Mapping Green Hydrogen and Renewable Energy Research in Extended BRICS (Brazil, Russia, India, China, South Africa and Others): A Bibliometric Approach with a Future Agenda

Abstract

Green hydrogen has emerged as a critical pillar of sustainable energy transitions, with its potential as a carbon-free fuel to decarbonize hard-to-electrify sectors while bolstering energy security. This study examines the trajectory of green hydrogen and renewable energy research within extended BRICS nations (the five core BRICS plus recent entrants) using bibliometric analysis, aiming to map publication trends, thematic focus, and collaborative networks from 2005 to 2024. A comprehensive dataset of 292 publications (2005–2024) was retrieved from Scopus. The results reveal a rapidly growing body of literature with an accelerating output in recent years and substantial citation impact. China leads in both publication volume and influence, followed by India and Russia, attesting to robust national research initiatives. Approximately one-quarter of the studies involve international co-authorship, underlining active collaboration among these countries and beyond. The novelty of this study lies in conducting the first comprehensive bibliometric analysis of green hydrogen and renewable energy research within the extended BRICS, highlighting publication trends, collaboration patterns, and thematic evolution to inform future research and policy development. These bibliometric insights offer valuable guidance for policymakers and industry stakeholders by highlighting core strengths (hydrogen production technologies) and pinpointing gaps where capacity-building is needed.

1. Introduction

Climate change and energy security concerns have made the global shift to renewable energy an urgent priority. According to the Intergovernmental Panel on Climate Change (IPCC, 2018), restricting global temperature rise to 1.5 °C demands urgent and extensive shifts within energy infrastructures worldwide underscoring the need to accelerate clean energy adoption. In this context, green hydrogen has risen to prominence as a sustainable energy carrier and a key pillar of decarbonization strategies. Produced via electrolysis powered by renewables, green hydrogen can replace fossil fuels in applications that are hard to electrify—such as heavy industry, long-haul transport, and seasonal storage—without emitting carbon dioxide. However, developing efficient and low-cost noble-metal-free photocatalysts remains one of the daunting challenges in low-cost H₂ production [1]. Many decarbonization scenarios now anticipate hydrogen playing an important role in achieving a net-zero level in the future, for example, the International Energy Agency (IEA, 2019) projects that hydrogen could meet roughly 12–13% of the global final energy demand by 2050. This growing optimism reflects hydrogen’s immense potential to drive the transition to a carbon-neutral world. Emerging economies in the extended BRICS group (Russia, China, South Africa, India, and Brazil) are central to the renewable energy transition due to their sheer scale and rapid growth. Collectively, the nation’s comprising BRICS represent approximately 40% of the global population and consume close to 40% of the world’s energy consumption, and they generate a substantial share of greenhouse gas emissions [2]. Their energy policies and innovation trajectories will thus heavily influence global decarbonization efforts. Recognizing this responsibility, BRICS nations have increasingly turned their focus toward renewable energy and green hydrogen development. China and India, in particular, have launched ambitious national hydrogen programs (e.g., China’s fuel cell vehicle plans and India’s National Hydrogen Mission), while Russia, Brazil, and South Africa are investing in pilot projects and strategies to harness green hydrogen for industrial use and export [3,4]. This momentum across the extended BRICS group points to their intention to become key players in the emerging hydrogen economy. Indeed, strengthening research and innovation in green hydrogen will be pivotal to positioning these nations at the forefront of the global transition toward sustainable clean energy.

Despite the growing importance of green hydrogen in the extended BRICS group, there is a notable gap in the literature when it comes to systematically mapping and understanding the research in this domain for these countries. To date, most bibliometric analyses of hydrogen energy have taken a global or technology-specific view, without a dedicated focus on the BRICS economies. For instance, Ref. [5] conducted a bibliometric study on green hydrogen production, storage, and utilization worldwide, demonstrating extensive research activity in sustainable hydrogen technologies. Similarly, various studies have reviewed renewable energy research trends in general (e.g., using bibliometric methods to analyze the water–energy–food nexus or renewable integration) without zooming in on the BRICS context. However, no prior work—to our knowledge—has specifically examined the evolution of the green hydrogen research within the extended BRICS nations as a distinct group. This represents a significant research gap, given that these countries’ trajectories in hydrogen R&D may differ from global patterns due to their unique economic, policy, and resource contexts. Addressing this gap is not only of academic interest but also of practical importance. A systematic mapping of the scientific literature in this domain can yield critical insights for policymakers, researchers, and industry stakeholders. By revealing who is publishing on green hydrogen, in what subtopics, and with what impact, such an analysis helps identify the strengths and weaknesses in the current knowledge base. It can inform decision-makers about where to channel resources or foster collaborations, and highlight opportunities for technology transfer and innovation. In essence, bibliometric mapping provides a mirror of the research landscape, helping stakeholders see the trends and networks that might otherwise remain obscure in the deluge of publications. Therefore, a bibliometric approach is an invaluable tool for understanding the progress of green hydrogen research in the extended BRICS group and for guiding its future development.

Based on the foregoing ideas, this study seeks to fill the noted gap by systematically analyzing the green hydrogen and renewable energy research landscape in the extended BRICS countries using bibliometric methods. Specifically, this study examines publications from 2005 to 2024 to characterize how this field has evolved in these emerging economies. We investigate publication trends, key sources of knowledge, collaborative networks, and the thematic structure of the research, with the goal of providing a wide-ranging and in-depth synthesis of green hydrogen research in the BRICS context. To guide this investigation, we pose the following research questions:

RQ1: How have annual scientific production and influence evolved between 2005 and 2024?

RQ2: Which sources are the most impactful, prominent, and dynamic in this field?

RQ3: How is the impact and collaboration of different countries distributed in this domain?

RQ4: What is the intellectual structure of the field, including the most influential documents, co-citation patterns, and the historiographic evolution of manuscripts?

RQ5: How is the conceptual structure of the research field characterized, based on elements such as TreeMap visualization, three-field plot (Countries–Keyword–Source), co-occurrence network, and thematic evolution?

By addressing these questions, this study provides a data-driven picture of green hydrogen and renewable energy research in the extended BRICS milieu. The novelty and originality of this study lie in its exclusive bibliometric focus on the extended BRICS nations—a region that has been largely overlooked in previous hydrogen energy analyses. Unlike prior global or technology-specific bibliometric reviews, this study systematically maps the green hydrogen research landscape in these emerging economies, providing the first evidence-based synthesis of publication trends, influential actors, and thematic developments within this strategic geopolitical bloc.

The subsequent sections of this manuscript are arranged in the order described below:

Section 2 presents a succinct literature review that synthesizes previous work on green hydrogen and renewable energy, highlighting both bibliometric studies and alternative review approaches. Section 3 describes the methodology, detailing the data collection process, filtering criteria, and the bibliometric tools used for performance, intellectual, and conceptual analysis. Section 4 reports the results, including publication trends, key metrics, and network visualizations. Section 5 discusses these findings in light of the policy implications and future research directions, and Section 6 brings the discussion to a close by recapping the main contributions and offering suggestions for future research. Finally, Section 7 presents the conclusion, summarizing the key findings, addressing the limitations, and suggesting future research directions for further exploration in the field.

2. Literature Review

The current research on green hydrogen and renewable energy is developing at a high speed because nations worldwide strive to progress toward sustainable carbon-neutral power systems. The production technique of green hydrogen through the electrolysis of water driven by renewable energy sources has made it appealing for the decarbonizing industry as well as transportation sectors and power generation facilities [6]. The worldwide adoption rate of RE technologies continues to increase because they help modernize the global energy system. The scientific field analyzes the research evolution of green hydrogen and renewable energy by developing several methods to explore challenges and opportunities. The most widely used methodology employed today is bibliometric analysis because it helps the researchers study research trends and thematic evolution and explore knowledge networks. Academic researchers in this field now embrace a diversity of review techniques encompassing systematic research with narrative reports and techno-economic breakdowns that support bibliometric measurements for more complete assessments. This literature review organizes the existing research into three fundamental sections, including bibliometric studies of GH beyond RE, bibliometric studies of RE beyond GH, and alternative review methods that cannot be restricted to bibliometric analysis.

2.1. Bibliometric Studies on Green Hydrogen Beyond Renewable Energy

Green hydrogen research has expanded its analysis from renewable energy applications into multiple technological aspects along with economic factors and policy considerations. Ref. [5] performed a bibliometric investigation of green hydrogen generation storage utilization, which demonstrated extensive research activity in sustainable hydrogen technologies. Research investigations focusing on green hydrogen production without RE dependence are evident in [6], who studied production systems and technological developments. Ref. [4] evaluated hydrogen production from water industries using bibliometrics, integrating circular economy perspectives. A bibliometric study and literature review by [7] delved into hydrogen production methodologies, emphasizing green and blue hydrogen as pivotal for future energy systems. The study discussed the potential of these technologies to significantly reduce greenhouse gas emissions. Ref. [8] used bibliometric analysis and state-of-the-art assessing photoanodes for green hydrogen production, emphasizing their environmental feasibility. Ref. [3] studied green hydrogen scientific literature through thematic mapping to reveal cooperation networks, which emphasized sustainability goals through, mainly, social network analysis (SAR) and a bibliometric technique.

2.2. Bibliometric Studies on Renewable Energy Beyond Green Hydrogen

The renewable energy research in multiple fields has become more prominent than its direct connection with green hydrogen emissions according to bibliometric research studies. Power system integration of renewable energy has received a broad analysis throughout multiple studies. Ref. [9] described two major difficulties when using Scopus data to model system complexities and define boundaries. The study by [10] utilized bibliometric methods to investigate the water–energy–food nexus, particularly its relationship to land use. Ref. [11], among other authors, conducted supply chain performance research, which mainly studied solar and wind energy systems to identify their logistical and economic barriers.

Ref. [12] examined multi-criteria decision models for a renewable energy evaluation while stressing the requirement to extend sustainability assessment indicators. Ref. [13] studied the development history of 100% RE systems modeling through an analysis of increasing publications. The study by [14] analyzed how artificial intelligence helps RE through its applications for solar and wind energy forecasting and stability assessments. Different research projects analyzed both RE sustainability and technological developments. The research by [15] through a bibliometric analysis showed theoretical modeling to be the primary focus area for ocean RE. The paper by [16] used a bibliometric analysis and systematic literature review based on Scopus and Web of Science data to compare renewable energy sources and sustainability aspects. The research into renewable energy in Africa shows specific trends according to [17], who identified solar power and rural power supply and economic development as major research areas. The research by [18] analyzed how renewable energy systems are applied in shipping but placed environmental advantages above monetary considerations. Ref. [19] analyzed how renewable energy sources contribute to energy conservation through green policy assessments.

Studies today highlight renewable energy’s significant contribution to attaining both economic sustainability as well as environmental sustainability. Ref. [20] conducted a study through bibliometric methods to investigate how renewable energy supports economic development in developing countries. Ref. [21] conducted a study to gauge RE research effects on environmental sustainability while describing the research collaborations through citation networks. Ref. [22] analyzed RE integration into economic systems while uncovering essential factors for deploying RE technologies. The research conducted by [23] examined how sustainable development relates to RE technology innovation processes. These studies demonstrate the various uses of renewable energy studies as they gain importance beyond their contribution to global heating.

2.3. Alternative Review Approaches in the Green Hydrogen and Renewable Energy Research Beyond the Bibliometric Approach

The valuable findings from the bibliometric analysis result in an enhanced understanding when combined with different review strategies. Both narrative and systematic reviews provide essential knowledge synthesis methods after bibliometric mapping has been completed. Ref. [24] conducted a qualitative synthesis that studied green hydrogen’s implementation in isolated communities while assessing them from both positive and negative perspectives as well as system decentralization hurdles. In a critical review, Ref. [25] examined the contributions of green hydrogen energy systems to achieving near-zero greenhouse gas emissions. The paper offered an in-depth evaluation of green hydrogen as a transformative alternative within renewable energy frameworks. Ref. [26] investigated green hydrogen socioeconomic elements through systematic review methods to establish how storage technology and blending practices alongside risk management will develop in the future. The mix of techno-economic assessments together with life cycle assessments produces vital information regarding the sustainable aspects of renewable energy and green hydrogen. The analysis conducted by [27] demonstrates how different methodological limitations influence the environmental effects observed when applying the life cycle assessment (LCA) alongside life cycle cost (LCC) to unitized regenerative fuel cells in green hydrogen applications. The analysis of policy frameworks along with socio-technical elements has been studied using other conceptual methods. Additionally, a systematic literature review by [28] analyzed societal acceptance and stakeholders’ perceptions of hydrogen technologies. The study provided insights into the social dimensions of hydrogen adoption, which is crucial for policy and implementation strategies.

3. Research Gap and Future Agenda

The work conducted by [29] serves as the main relevant research regarding our topic because it applies a bibliometric method to combine green hydrogen and renewable energy throughout all countries from 2018 to 2022. The publications from the expanded BRICS region make up nearly one-third of total field publications while only constituting 5% of world countries according to [30]. This observation caught the attention and underscores the uniqueness of this study focusing on this narrower region. This study extends the duration covered from [29] by using the same bibliometric analytical approach. Additional detailed bibliometric studies about evolving research trends and policy-driven research connections and collaborative relationships need to be analyzed in this specific geopolitical context. Additional studies must be performed to achieve a thorough examination of technological developments and socioeconomic difficulties together with environmental factors. Future research needs to establish the geographical mapping of green hydrogen and renewable energy research in the expanded BRICS region while evaluating its effects on regional energy policies and developing sustainable transition tactics for these economies.

4. Methodology, Tools, and Materials

4.1. Data Collection

To conduct this bibliometric study on green hydrogen and renewable energy research within the extended BRICS group, we retrieved data from the Scopus database. SCOPUS was selected for its extensive coverage of scientific materials [30,31]. The search strategy was formulated using two sets of descriptors to ensure a comprehensive dataset (see

Table 1. Sets of descriptors used in the search query.

Set 1	Set 2
Green hydrogen	Renewable energ *
Hydrogen production	Renewable sources
Green hydrogen	Solar energ*
Hydrogen fuel cells	Wind power
Hydrogen technolog *	Renewable energ * integration
Green hydrogen econom *	Renewable energ * policies

Note: * is used to include all the possible endings of a descriptor, for instance, energ * includes “energy”, “energies”, “energical”, etc.

).

The search query applied in Scopus was as follows:

((“Green hydrogen” OR “Hydrogen production” OR “Green hydrogen” OR “Hydrogen fuel cells” OR “Hydrogen technolog*” OR “Green hydrogen econom*”) AND (“Renewable energ*” OR “Renewable sources” OR “Solar energ*” OR “Wind power” OR “Renewable energ* integration” OR “Renewable energ* policies”)).

It is important to note that the search was designed to broadly encompass green hydrogen research, without restricting the dataset to specific production methods, such as electrocatalytic or photocatalytic water-splitting. This approach ensures a comprehensive overview of the research trends across technological, economic, and policy dimensions.

The term renewable energy was included to ensure the dataset captured studies explicitly linking green hydrogen to renewable sources, such as solar, wind, and biomass-based energy systems, rather than limiting it to electrochemical or photochemical processes alone.

4.2. Data Processing Following the PRISMA Approach

We processed the retrieved the data through the PRISMA approach according to Figure 1. Simultaneously, 623 documents were found in the Scopus database search. A total of 572 manuscripts, which appeared between 2005 and 2024, were considered for analysis after applying the filtering process, but 51 records were excluded, which had publication dates in the range of 1972–2004 and 2025. A further inspection reduced the comprehensive dataset to 292 documents after eliminating 280 publications that stemmed from countries beyond the BRICS intercontinental group, however the 292 papers included the core BRICS countries, Brazil, Russia, India, China, and South Africa, along with Argentina, Egypt, Ethiopia, Iran, Saudi Arabia, and the United Arab Emirates. The analysis included different document categories, including articles, conference papers, book chapters and reviews, and data papers and books. All these types of documents were used in both qualitative and quantitative bibliometric analyses.

4.3. Main Keys in Bibliometric Studies

Various essential bibliometric indicators served as the basis for the analysis. A research trend analysis was established through published annual production metrics and influence evaluations between 2005 and 2024. This research evaluated powerful and changing sources within the field while investigating international collaboration patterns and country impact distributions. Co-citation analysis along with the identification of the top influential documents and manuscript historiographic evolution produced the intellectual mapping of the research domain. This research utilized treemaps together with three-field plots that connected countries to keywords and sources as well as co-occurrence networks to analyze conceptual structures and thematic time-sensitive changes. The proposed research framework system tracks every aspect of green hydrogen and renewable energy studies in extended BRICS territories and helps create future policy frameworks.

5. Results

5.1. Description Statistics

$$\mathrm{Annual} \mathrm{Growth} \mathrm{Rate} (\%)=\left({\left({\displaystyle \frac{\mathrm{N}\mathrm{t}}{\mathrm{N}0}}\right)}^{{\displaystyle \frac{1}{\mathrm{t}}}}-1\right) \mathrm{\times } 100$$

How: Nt: Number of documents in the last year, N0: Number of documents in the first year, t: Number of years between the first and last publication year

Average Age = Current Year − (∑Publication Year of Each Document/Total Number of Documents)

Average Citations per Doc = (Total Number of Citations/Total Number of Documents)

From

Table 2. Dataset main information.

Description	Results
Main information About Data
Timespan	2005:2024
Sources (Journals, Books, etc.)	139
Documents	292
Annual Growth Rate %	27.22
Document Average Age	3.45
Average Citations per Doc	25.29
Keywords Plus (ID)	2064
Author’s Keywords (DE)	800
Authors	981
Authors Collaboration
Single-Authored Docs	7
Co-Authors per Doc	4.67
International Co-Authorships %	25.68

Note: the calculation was powered by Bolioshiny based on R Language.

, it can be seen that this research incorporates 292 publications between 2005 and 2024 that originated from 139 sources, including books and journals. The documents found in the dataset have existed for 3.45 years on average, implying that the analysis includes older academic literature than that in Table 1. The 27.22% growth rate shows steady growth based on publications from 2005 to 2024 at a slower pace than the data from the first analysis. The academic recognition of these works is greater in this dataset since the researchers cited each document at an average of 25.29 times. The collection contains 2064 Keywords Plus (ID) and 800 Author’s Keywords (DE), which demonstrate extensive thematic variety. Authors Collaboration: The dataset contains 981 authors who typically collaborate for research instead of working solo because there are only seven authors who published single-authored documents. The number of researchers involved in writing each document reaches 4.67 on average while maintaining a similar collaborative approach as before. International co-authorship appears in 25.68% of the documents, indicating a strong trend toward an academic collaboration between researchers from different countries.

5.2. Annual Scientific Production and Influence Evolution

• Annual production (2005–2024)

The academic research flow in this field is presented through a cumulative rate curve spanning 2005 to 2024. Within the Figure 2. the line indicates the overall trend during this period whose mathematical description is y = 0.0337 × −0.1817, while R² = 0.5991 confirms a moderate association between the variables. The cumulative rate shows gradual growth throughout the period in 2005–2012. Cumulative academic production reached 3.42% during the period from 2008 to 2008, which showed moderate research activity. This gradual trend continues until 2012. During 2013 through 2017, there was a sustained upward development in academic productivity. Academic productivity data between 2014 and 2017 generated a 6.85% increase followed by a 12.67% rate at the end of the period. The persistent growth pattern shows academic productivity has been improving in this studied time span. The rise in the cumulative rate becomes steeper between 2018 and 2020 because it reaches a value of 20.89% in 2020. The starting point for increased academic output emerges during this phase. The research data demonstrate maximum expansion during the time period from 2021 to 2024. From 2022 to 2023, the cumulative rate increases dramatically from 29.45% to 66.78% before reaching 100% by 2024. The analysis shows that the academic work volume achieved 33.22% of its total output during this time frame, which represents a significant productivity breakthrough, possibly because of technological progress funding and strategic approaches. The sharp growth in academic productivity indicates a transformational phase in which the researchers dedicated themselves to making research contributions and improving their productivity levels. Further research efforts will reveal the particular elements that motivated this outstanding increase.

• Annual influence (2005–2024)

Table 3. Citations per Publication (ACP) and Citations per Year (ACY) over time.

Year	N	ACP	ACY
2005	1.00	0	0.00
2006	1.00	2	0.10
2009	5.00	7.8	0.46
2010	3.00	45.67	2.85
2012	3.00	12	0.86
2013	3.00	38.33	2.95
2014	1.00	74	6.17
2015	3.00	112	10.18
2016	3.00	25	2.50
2017	9.00	70.44	7.83
2018	5.00	229.4	28.68
2019	13.00	39	5.57
2020	11.00	44.09	7.35
2021	25.00	22.64	4.53
2022	45.00	38.11	9.53
2023	64.00	17.64	5.88
2024	97.00	3.99	2.00

Note: ACP = Average Citation per Document; ACY = Average Citation per year.

highlights the trends in Average Citations per Publication (ACP) and Average Citations per Year (ACY) from 2005 to 2024, revealing notable fluctuations. ACP numbers together with ACY numbers remained steady at low levels in 2005–2009, yet exhibited a modest improvement trend throughout that period. From 2010 to 2015, ACP rose to 112 alongside ACY reaching its highest point of 10.18 as ACP and ACY demonstrated exceptional analysis performances. During the 2016 to 2020 period, the citation impact showed fluctuations that caused a noticeable decline in 2020. During the time span of 2021 to 2024, there was a steep fall in both ACP and ACY. The decline could be explained by growing field competition or changing citation norms as well as increased numbers of published articles. The recent years show declining citation rates that call for additional research to determine the root causes behind this trend change.

5.3. Impactent, Prominent, and the More Dynamic Sources

Based on

Table 4. Most impactful and prolific sources.

Element	TC	TC Rank	NP	NP Rank	H_Index	G_Index	M_Index	PY_Start
International Journal of Hydrogen Energy	2088	1	47	1	23	45	1.438	2010
Energy Conversion and Management	811	2	15	2	13	15	1.444	2017
Renewable and Sustainable Energy Reviews	369	3	3	7	3	3	0.333	2017
Sustainable Energy Technologies and Assessments	206	4	6	5	5	6	0.714	2019
Applied Energy	174	5	5	6	3	5	0.500	2020
Energy	172	6	7	4	6	7	0.545	2015
Journal of Materials Chemistry A	152	7	3	7	3	3	0.231	2013
Renewable Energy	127	8	9	3	5	9	0.833	2020
Solar Energy	106	9	3	7	3	3	0.300	2016
Journal of cleaner Production	87	10	3	7	3	3	0.750	2022

Note: TC = total citation, number of paper, and PY_start = journal’s start year.

, the BRICS region demonstrates distinct strengths through the three top sources explained in

Table 5. Contribution of corresponding author’s countries.

Country	Articles	SCP	MCP	Freq	MCP_Ratio
China	149	129	20	0.51	0.134
India	19	15	4	0.065	0.211
Egypt	12	6	6	0.041	0.5
Iran	11	9	2	0.038	0.182
Brazil	7	5	2	0.024	0.286
Saudi Arabia	6	5	1	0.021	0.167

Note: SCPs = single corresponding author papers; MCPs = multiple corresponding author papers.

that make significant contributions to green hydrogen and renewable energy. The International Journal of Hydrogen Energy serves as the top source in the research community due to its highest total citations of 2088 paper count at 47 and h-index of 23, which proves its key role in advancing the research of green hydrogen specifically. The journal Energy Conversion and Management positions itself in second place by accumulating 811 total citations (TCs) while maintaining a moderate 15 number of papers (NPs), which demonstrates its ability to produce influential research. The research journal maintains an h_index value of 13 that demonstrates a substantial scholarly impact on both green hydrogen and renewable energy fields. The Renewable and Sustainable Energy Reviews earns the third place in TCs with 369 citations from only three published papers that place it 7th place in the NPs rankings. The journal demonstrates an outstanding impact through each article it produces, which focuses on critical subjects in Renewable Energy research. Its h_index of three underscores its limited but highly influential contributions. These journals demonstrate diverse approaches to progress in and RE by emphasizing either high productivity and consistent impact or the selective publication of high-impact research within the BRICS territory.

Trends in the dataset show an increasing interest in green hydrogen and renewable energy in these journals, due to several motives, such as the growing concerns over the necessity for cleaner energy, such as green hydrogen and climate change solutions. The depicted data in Figure 3 and Table 4 add researchers, authors, and editor boards teams to understand the trends in the field and present research projects and publications for the future. Positively, all these journals have been recorded as specialist publications in the scope of hydrogen and/or energy.

5.4. Distribution of Countries’ Impacts and Collaboration

5.4.1. Most Authors’ Citations by Country

Figure 4 demonstrates that China dominates the field through its substantial 3506 citations, which exceed those of other countries. The research field shows India and Iran along with Egypt experiencing increasing importance as demonstrated by their rising citation numbers (513, 382, and 369, respectively). The research output from Brazil, Saudi Arabia, South Africa, Ethiopia, and Argentina is lower than the other nations in the green hydrogen and renewable energy research. Research activities in China currently dominate the field, but India together with Iran and Egypt demonstrate a growing research influence. Research impact development opportunities remain available to various countries.

5.4.2. Distribution of Articles and Corresponding Author Types

As Figure 5 and Table 5 indicate, China leads all other countries by producing 149 research articles, which account for 51% of the total studies analyzed. India stands as the second-largest contributor to the research output with 19 articles (6.5% of the total) after China. The remaining countries, including Egypt, Iran, Brazil, and Saudi Arabia, produced fewer articles ranging from 6 to 12 papers. Among the countries analyzed, the data reveal an important pattern regarding the distribution of single corresponding author papers (SCPs). SCPs make up 87% of all articles in China, which accounts for 129 out of its total 149 publications. The majority of scientific papers in India (78.9%) and Iran (81.8%) have a single corresponding author as their leader. Egypt along with Brazil demonstrates an almost equal distribution of SCPs and MCPs.

5.4.3. Collaboration Trends and MCP Ratios

The data indicate that Egypt and India demonstrate elevated MCP ratios due to their patterns of collaborative research. Egypt demonstrates a 50% multiple corresponding author paper ratio in their research by presenting six articles with multiple authors (6 out of 12 articles). The MCP ratio in India reaches 21.1%, which indicates moderate circumstances of multi-author research collaboration. The research collaboration in Brazil and Saudi Arabia extends beyond one corresponding author but remains lower than other countries at 28.6% and 16.7%, respectively. China presents the lowest multi-corresponding author percentage ratio at 13.4% because its science output depends mainly on single authors. The MCP ratios demonstrate that Egypt leads the collaborative research, while China and Iran conduct their studies independently.

5.4.4. Insights into Research Collaboration and Future Trends

Research practices among the countries of extended BRICS show distinctive patterns according to the statistical findings. The extensive number of articles published by China does not translate to equal collaboration levels since MCPs are less common in the Chinese research, thus indicating that the Chinese research operates as a standalone system, which avoids international cooperation. Egypt demonstrates a higher engagement in worldwide research networks through its MCP ratio, which exceeds that of other nations, specifically in green hydrogen and renewable energy fields. The research landscape of India demonstrates strong international potential because 21.1% of its scientific papers include multiple corresponding authors. The article counts for Brazil and Saudi Arabia remain low indicating these countries might pursue additional international research connections in the future. Future research collaboration trends show evidence that Egypt and India will become leading partners in international joint research projects because of their elevated MCP ratios.

5.5. Intellectual Structure

Intellectual structure refers to the network of knowledge that outlines a research area by recognizing the most influential works, authors, and theoretical foundations. The aim of analyzing the intellectual structure is to explore the knowledge base by determining when the most-cited works and their authors (including institutional affiliations) emerged and how they have influenced the field. This analysis is primarily based on co-citation networks, historiography, and bibliographic coupling, which help visualize the connections between academic contributions. By mapping these relationships, it reveals the evolution of knowledge, major schools of thought, and shared or divergent research themes. Additionally, the findings from this analysis provide a structured summary of the field’s intellectual development, highlighting key paradigms and theoretical frameworks. The comprehensive approach not only identifies the most influential contributions but also encapsulates various intellectual perspectives, ultimately offering insights that guide future research and reveal knowledge gaps.

5.6. Most-Influential Documents

Table 6. Most-influential works.

Paper	Title	Journal	DOI	TC	TC Rank	ACY	ACY Rank
Chi J, 2018	Water electrolysis based on renewable energy for hydrogen production	Cuihua Xuebao Chin J Catalysis	https://doi.org/10.1016/S1872-2067(17)62949-8	1044	1	130.50	1
Amin M, 2022	Hydrogen production through renewable and non-renewable energy processes and their impact on climate change	Int J Hydrogen Energy	https://doi.org/10.1016/j.ijhydene.2022.07.172	320	2	80.00	2
Kalinci Y, 2015	Techno-economic analysis of a stand-alone hybrid renewable energy system with hydrogen production and storage options	Int J Hydrogen Energy	https://doi.org/10.1016/j.ijhydene.2014.10.147	289	3	26.27	7
Singh A, 2017	Techno-economic feasibility analysis of hydrogen fuel cell and solar photovoltaic hybrid renewable energy system for academic research building	Energy Convers Manage	https://doi.org/10.1016/j.enconman.2017.05.014	210	4	23.33	8
Wang M, 2019,	Review of renewable energy-based hydrogen production processes for sustainable energy innovation	Glob Energy Interconnect	https://doi.org/10.1016/j.gloei.2019.11.019	198	5	28.29	6
Qolipour M, 2017	Techno-economic feasibility of a photovoltaic-wind power plant construction for electric and hydrogen production: A case study	Renewable Sustainable Energy Rev	https://doi.org/10.1016/j.rser.2017.04.088	164	6	18.22	9
Khan T, 2022	Review on recent optimization strategies for hybrid renewable energy system with hydrogen technologies: State of the art, trends and future directions	Int J Hydrogen Energy	https://doi.org/10.1016/j.ijhydene.2022.05.263	143	7	35.75	5
Bhattacharyya R, 2017	Photovoltaic solar energy conversion for hydrogen production by alkaline water electrolysis: Conceptual design and analysis	Energy Convers Manage	https://doi.org/10.1016/j.enconman.2016.11.057	131	8	14.56	10
Chen H, 2023	Low-carbon economic dispatch of integrated energy system containing electric hydrogen production based on VMD-GRU short-term wind power prediction	Int J Electr Power Energy Syst	https://doi.org/10.1016/j.ijepes.2023.109420	124	9	41.33	3
Li X, 2023	Latest approaches on green hydrogen as a potential source of renewable energy towards sustainable energy: Spotlighting of recent innovations, challenges, and future insights	Fuel	https://doi.org/10.1016/j.fuel.2022.126684	124	9	41.33	4

showcases the important research contributions, which guide studies on green hydrogen and renewable energy throughout the BRICS extended region and additional countries. Among the publications from 2018 and prior dates, there exists a higher TC count compared to newer papers because they acquired additional time to attract citations and impact their field. The scientific manuscript “Water Electrolysis Based on Renewable Energy for Hydrogen Production” by CHI J gained 1044 citations, which earned it the title of top paper within the dataset. This research paper maintains a strong and active role in hydrogen production studies as demonstrated by its 130.50 Average Citations per Year indicator. The dark fermentation method for bio-hydrogen production published by Amin M shows rapid, increasing interest with 320 citations along with an 80.00 citations per year average. Among the recent publications, Chen H, and Li X, achieved a citation average of 41.33 each year since their release. The dataset encompasses several areas in hydrogen production and renewable energy through studies about electrolysis and catalytic advancement (Chi J and Li X), hydrogen production methods from biomass and organic waste (Amin M, and Qolipour M), and techno-economic and life cycle assessments (SINGH A and BHATTACHARYYA R) with sustainable energy systems and global energy interconnections (Wang M). The research into hydrogen production and renewable energy maintains its essential role in developing sustainable energy solutions because these studies receive numerous citations, and new publications demonstrate strong potential to direct upcoming discussions.

5.7. Historiographic Evolution of Manuscripts

The term historiographic analysis defines the total number of occurrences a research work receives within a predetermined bibliometric range according to [32]. Through the extraction of paper text titles along with keywords, the researchers can analyze citation patterns to determine which search scopes boost work citations combined with their chronological positioning in the research network. The definition complements the broader historiographic research in bibliometrics since it tracks how the academic literature develops throughout time. Historiographic analysis produces its findings through evaluations of the Local Citation Score (LCS) and Global Citation Score (GCS) that measure scholarly influence. The LCS optimizes field-specific key work identification by studying citation patterns in chosen datasets; therefore, it allows scholars to track the historical development of research ideas among specific academic groups. The GCS provides an evaluation of a work’s total disciplinary influence, which helps recognize the foundational research that defines major academic fields of study. The researchers use the LCS and GCS comparison to distinguish between works that significantly influence narrow domains (a high LCS and low GCS) from important studies that impact multiple domains (a high GCS and high LCS) in historiographic mapping. Bibliometric historiography creates intellectual field history by examining information from citation networks as well as co-citation relationships alongside authorship patterns and journal influence combined with keyword shifts to reconstruct research field development. Historiographic analysis established by [32] offers researchers a numerical system that evaluates scholarly impact through bibliometric historiography, which places these findings within academic evolution patterns to reveal academic contribution effects on evolving knowledge systems.

In

Table A1. Historiographic evolution of manuscript.

Paper	Title	Author_Keywords	Year	LCS	GCS
Sharma Rs, 2005, Proc Sol World Congr: Bringing Water World, Incl Proc Ases Annu Conf Proc Natl Passive Sol Conf	Conceptualization of renewable energy balancing cycle (REBC) for hydrogen production and mitigation of the global warming through solar thermal power generation	convergence schemes; hydrogen production; pressurized volumetric air receiver technology; renewable energy balancing cycle (REBC); ut-3 process	2005	0	0
Chen X-R, 2006, Huagong Xiandai	Research progress in hydrogen production from water on photocatalysts with solar energy	hydrogen production; photocatalysts; solar energy; water decomposition	2006	0	2
Gao B, 2009, Wnwec—World Non-Grid-Connected Wind Power Energy Conf	Analysis of a non-grid-connected wind power-seawater desalination and hydrogen production base distribution in China	distribution; hydrogen production industry; non-grid-connected wind power; seawater desalination	2009	0	2
Jin C, 2009, Wnwec—World Non-Grid-Connected Wind Power Energy Conf	Wind energy exploitation and hydrogen production bases construction applying non-grid-connected wind power in jiangsu coastal areas	hydrogen production base; non-grid-connected; wind energy	2009	0	0
.....	.....	.....	…
He L, 2024, Manuf Serv Oper Manage	From curtailed renewable energy to green hydrogen: infrastructure planning for hydrogen fuel cell vehicles	green transportation; hydrogen fuel cell vehicles; infrastructure planning; power systems	2024	0	1
Mohammadi Z, 2024, Int J Hydrogen Energy	An innovative transient simulation of a solar energy system with a thermochemical hydrogen production cycle for zero-energy buildings	hydrogen; optimization; thermochemical cycle; trnsys software; zero-energy buildings	2024	0	2
Gupta M, 2024, Proc—Int Conf Comput Model, Simul Optim, Iccmso	A comparative study and mathematical modeling of pbucp using renewable energy sources and hydrogen fuel cell vehicle	hydrogen fuel cell vehicle; profit based unit commitment problem; renewable energy sources; unit commitment	2024	0	0
Hong C, 2024, Int J Hydrogen Energy	Layout optimization of the “pipe + ship” transmission network for the decentralized offshore wind power-hydrogen production	decentralized offshore wind power-hydrogen production; hydrogen transmission network; layout optimization; location−allocation problem; pipe-ship hybrid mode; shipping route optimization	2024	0	4
Qi X, 2024, Int J Hydrogen Energy	Energy, exergy, exergoeconomic and exergoenvironmental analyses of a hybrid renewable energy system with hydrogen fuel cells	energy storage; exergoeconomic; exergoenvironmental analysis; renewable energy systems	2024	0	14
Pal P, 2021, Renewable Sustainable Energy Rev	Off-grid solar photovoltaic/hydrogen fuel cell system for renewable energy generation: an investigation based on techno-economic feasibility assessment for the application of end-user load demand in north-east india	cost of energy; fuel cell; hydrogen production; net present cost; photovoltaic	2021	0	95
Luo Z, 2022, Int J Hydrogen Energy	Hydrogen production from offshore wind power in south China	hydrogen production; offshore wind power; water electrolysis	2022	0	88

(See Appendix A), the historiographic analysis explores the research development of green hydrogen and renewable energy across extended BRICS nations through four important phases.

• The research period from 2005 to 2012 introduced basic concepts about producing hydrogen from solar power and wind power along with biomass energy sources. Gao, Jin, and He conducted research that studied how non-grid wind power could produce hydrogen alongside seawater desalination operations. Large-scale production of hydrogen using wind energy and bio-ethanol and solar energy in 2012 became the basis for additional advancements.
• Researchers began testing new experimental technologies that combined photocatalysis with biomass gasification and wind power hybrid systems during the years from 2013 to 2017. The studies evaluated the financial attractiveness of independent renewable hydrogen systems and presented results that supported BRICS countries pursuing diverse energy systems, what Kalinci figured in his work (Appendix A).
• Economic viability and efficient operations along with grid connectivity became the primary areas of study from 2018 to 2020. The research analyzed three methods for large-scale hydrogen optimization, which included chemical-looping hydrogen production alongside seawater electrolysis combined with biogas reforming. The implemented methods provided BRICS nations solutions to their energy access inequalities by optimizing their exploitation of renewable energy sources.
• Recent studies from the year 2021 to the present day focus on several essential aspects of hydrogen commercialization combined with policy development and infrastructure establishment for large-scale production. Studies investigate off-mains solar PV–hydrogen fuel cell systems, as described by the paper of Pal (See Appendix A), and offshore wind-based hydrogen production according to the work of Luo (consult Appendix A). Future research in 2023–2024 will concentrate on three areas: decreasing the carbon footprint through improved hydrogen supply chain management while establishing global market links.

For future research directions, green hydrogen production predicts the extended BRICS nations to become global leaders through their large-scale transformation from the experimental research to standardized economic developments. Key future research areas include:

-

Hydrogen infrastructure development and supply chain optimization studies should focus on finding ways to decrease costs when producing electrolysis systems and renewable hydrogen power.

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Hydrogen storage solutions and energy security policies.

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International cooperation for hydrogen trade and technology transfer.

5.8. Conceptual Structure

During bibliometric analysis, the conceptual structure demonstrates how researchers organize intellectual knowledge by showing how different concepts relate to themes and topics across literature collections. The mapping system serves a critical function to observe knowledge development patterns and establish research direction trends. The two central components for understanding conceptual structure consist of co-word analysis alongside thematic mapping. The fundamental relationship between keywords in co-word analysis uses network visualization to display keyword clusters, which helps identify main topics and their connections. Research topics receive classification during thematic mapping, which assigns them to three distinct categories, such as motor themes, emerging themes, and niche themes, using diagrams based on density and centrality. Both TreeMap visualization and its corresponding representation enable the researchers to view hierarchical research themes in a dynamic interface that showcases dominant and new academic areas in a research domain.

5.8.1. TreeMap

The TreeMap technique shows the actual term frequencies proportional to their importance in studies about green hydrogen and renewable energy within the expanded BRICS framework. The research field emphasizes hydrogen production as its most important subject because it appears 23% of the time in the analysis, as is shown in Figure 6 and Figure 7. The trend toward hydrogen generation methods represents an essential part in building sustainable energy systems. The second most-important topic in this investigation pertains to renewable energy with a frequency of 16% as it demonstrates how green hydrogen can be integrated into sustainable energy systems. The research foundation built upon hydrogen receives special recognition with ten percent occurrence throughout this academic field. The production methods, including solar energy at 11%, water electrolysis at 5%, and electrolysis at 4%, demonstrate the importance of renewable energy sources together with electrochemical methods for hydrogen generation. Wind power along with offshore wind power establish their significance within the hydrogen economy through appearance data at 4% and 3%, respectively. The prominence of “Green Hydrogen” (7%) highlights a significant focus on environmentally sustainable hydrogen production within BRICS nations. The fundamental research spans three areas through the appearance of “Fuel Cell” (3%), “Hydrogen Energy” (3%), “Energy Storage” (3%), and “Optimization” (2%). These concepts concentrate on hydrogen applications through fuel cells, hybrid energy storage systems, and optimization techniques. Solar system research occurs through the exploration of photovoltaic technology (2%) within the field of hydrogen production. TreeMap provides evidence of intensive academic research activities that focus on hydrogen manufacturing techniques together with renewable energy system integration. The visual structure helps to develop the overall paper’s structure by presenting the main themes and new directions, which will drive future green hydrogen and renewable energy strategies in BRICS nations.

5.8.2. Three-Field Plot Countries: Keyword Source

The three-field Sankey chart in Figure 8 displays the interconnected relationships of Countries (AU_CO), Keywords (ID), and Sources (SO) through its rectangular-node representations and line placement. The height values of the rectangular nodes show how often particular connections occur, and the width measurements on links describe the relationship strengths between nodes. China discovered itself as the leading influence in all three areas during the analysis. Hydrogen Production and Solar Power Generation stand among the leading Keywords in which the Topic is connected while the International Journal of Hydrogen Energy serves among its primary information sources. The analysis placed India in second place because its influence is strong in Solar Energy and Wind Power and it supports important Sources, including Energy Conversion and Management. The research of Iran, Saudi Arabia, Brazil showed average performances through connections with productive Sources as well as relevant Keywords. The Keyword Hydrogen Production stood out as the most frequently used term because it demonstrated a strong link between China and other leading countries while also gaining prominence through its appearances in the International Journal of Hydrogen Energy. The combination of Solar Power Generation and Renewable Energies functioned as notable Keywords, which demonstrate worldwide significance. The keywords Electrolysis and Wind Power represented supplemental research areas, but occurred with reduced frequency compared to other keywords. The International Journal of Hydrogen Energy proved to be the most significant source, which linked strongly to various countries while connecting to multiple Keywords. The reviewed Sources Energy Conversion and Management and Taiyangneng Xuebao (Solar Energy Journal) along with the Sustainable Energy Technologies and Assessments Journal demonstrated their dedication to sustainable renewable energy systems. Overall, Figure 8 demonstrates a significant collaborative effort in the renewable energy research, with China leading the contributions across all fields. The focus on hydrogen production and the related areas reflects a global interest in advancing sustainable energy solutions. Leading Sources, particularly the International Journal of Hydrogen Energy, play a pivotal role in disseminating this research, showcasing the interconnected nature of the global research network in fostering innovation in hydrogen and renewable energy technologies.

5.8.3. Co-Occurrence Network

Bibliometric analysis uses co-occurrence networks as essential tools for visualizing and analyzing the relationships and connections between keywords and concepts from the research publications. The method works to determine significant research themes by studying common keyword patterns, which indicate primary-knowledge areas in the studied domain. The map created by this network system presents the conceptual framework of a discipline by showing the alignments between the research concepts, thereby delivering complete intellectual mapping that promotes subfield detection. The research theme intellectual organization becomes the focus of a co-occurrence analysis that works through Biblioshiny’s network evaluation of keywords. This approach utilizes author keywords together with keyword plus elements from different databases to produce a systemic understanding of diverse research domains with their connected elements. The evaluation exhibits networks of common keyword occurrences, which display the relationship structures in both green hydrogen and renewable energy domains. Each research cluster includes systematically positioned keywords, which create unified stories and help the researchers grasp complex green hydrogen and renewable energy developments. This research design simultaneously detects literature-connected disciplines while revealing unexplored areas in the academic publications and delivers a comprehensive method to study research field development and structure [33,34,35]

This research shows Cluster 1 as the largest cluster with 20 nodes while using a red-color designation (Figure 9 and

Table 7. Co-occurrence words.

Node Color	Cluster Name	Nodes
Red	Hydrogen Technologies and Applications	Hydrogen Production, Renewable Energy, Solar Energy, Water Electrolysis, Wind Power, Hydrogen, Energy Storage, Electrolyzer, Hydrogen Storage, Water Splitting, Fuel Cell
	Renewable Energy Systems and Techniques	Biomass, Renewable Energy Sources, Organic Rankine Cycle, Photocatalysis, Non-grid-connected, Photovoltaic, Hydrogen Production System, Exergy Analysis, Wind Power Generation
Blue	Advanced Hydrogen and Emerging Technologies	Green Hydrogen, Offshore Wind Power, Hydrogen Energy, Optimization, Wind Energy, Green Ammonia, Electrolysis, Green Hydrogen Production
Green	Economic and Strategic Analysis	Economic Analysis

). This cluster splits into two smaller clusters that demonstrate its different topics. The first sub-cluster, “Hydrogen Technologies and Applications”, focuses on core areas, such as Hydrogen Production, Renewable Energy, Solar Energy, Water Electrolysis, Energy Storage, and Fuel Cell. The group of keywords demonstrates the research about green hydrogen production along with energy storage mechanisms alongside the cutting-edge hydrogen technology advancement toward hydrogen economic systems. The second sub-cluster, “Renewable Energy Systems and Techniques”, depicts the backing technologies of Biomass together with Renewable Energy Sources and Photovoltaics and the Organic Rankine Cycle, which demonstrate the integration of multiple renewable energy systems during hydrogen production. The combination of these sub-clusters demonstrates how green hydrogen plays an essential part in all BRICS energy transition operations since it advances both decarbonization initiatives and sustainable development needs. Cluster 2, which appears in blue, represents eight nodes while having the name “Advanced Hydrogen and Emerging Technologies”. This research focuses on high-tech GH production through various keywords, including Green Hydrogen, Offshore Wind Power, Hydrogen Energy, Optimization, and Electrolysis. The cluster shows innovation techniques for using renewable wind energy sources along with optimizations to maximize the performance and broad applicability of hydrogen production methods. The BRICS countries use emerging technologies, such as Green Ammonia and Electrolysis, to advance their pursuit of diversified hydrogen generation strategies while recognizing technological advances as fundamental to implementing hydrogen adoption. A single node in the green cluster of Cluster 3 performs Economic and Strategic Analysis. The Economic Analysis cluster demonstrates how strategic research in green hydrogen should focus on affordable solutions that embed hydrogen technologies into a sustainable transition process. The BRICS nations face a strategic need to merge economic development with sustainable targets for promoting regional and worldwide green hydrogen adoption.

This research shows Cluster 1 as the largest cluster with 20 nodes while using a red-color designation (Figure 9 and Table 7). This cluster splits into two smaller clusters that demonstrate its different topics. The first sub-cluster, “Hydrogen Technologies and Applications”, focuses on core areas, such as Hydrogen Production, Renewable Energy, Solar Energy, Water Electrolysis, Energy Storage, and Fuel Cell. The group of keywords demonstrates the research about green hydrogen production along with energy storage mechanisms alongside the cutting-edge hydrogen technology advancement toward hydrogen economic systems. The second sub-cluster, “Renewable Energy Systems and Techniques”, depicts the backing technologies of Biomass together with Renewable Energy Sources and Photovoltaics and the Organic Rankine Cycle, which demonstrate the integration of multiple renewable energy systems during hydrogen production. The combination of these sub-clusters demonstrates how green hydrogen plays an essential part in all BRICS energy transition operations since it advances both decarbonization initiatives and sustainable development needs. Cluster 2, which appears in blue, represents eight nodes while having the name “Advanced Hydrogen and Emerging Technologies”. This research focuses on high-tech GH production through various keywords, including Green Hydrogen, Offshore Wind Power, Hydrogen Energy, Optimization, and Electrolysis. The cluster shows innovation techniques for using renewable wind energy sources along with optimizations to maximize the performance and broad applicability of hydrogen production methods. The BRICS countries use emerging technologies, such as Green Ammonia and Electrolysis, to advance their pursuit of diversified hydrogen generation strategies while recognizing technological advances as fundamental to implementing hydrogen adoption. A single node in the green cluster of Cluster 3 performs Economic and Strategic Analysis. The Economic Analysis cluster demonstrates how strategic research in green hydrogen should focus on affordable solutions that embed hydrogen technologies into a sustainable transition process. The BRICS nations face a strategic need to merge economic development with sustainable targets for promoting regional and worldwide green hydrogen adoption.

For the future, the co-occurrence network analysis reveals important research trends for GH and RE within BRICS countries, which include three main points: (1) BRICS nations will develop advanced production techniques through electrolysis and renewable energy integration for expanding their growing energy needs. (2) The implementation of innovative renewable platforms, including wind power together with solar power along with biomass methods for hydrogen generation, benefits BRICS countries due to their high availability of clean energy sources. (3) Management of economic factors together with policy development must proceed in order to advance sustainable energy transitions through hydrogen-based systems. (4) The production of hydrogen for global environmental targets sustainable demands along with decarbonized methods that minimize emissions. (5) Life cycle analysis takes place alongside enhanced attention to minimize GH system carbon footprints to achieve maximum environmental advantages and an independent energy status. This research evaluation demonstrates both the combined nature of green hydrogen and renewable energy science through BRICS frameworks as well as the essential innovative and strategic elements for hydrogen-powered sustainability.

5.8.4. Thematic Evolution

This research presented essential themes about green hydrogen and renewable energy across different timeframes in the extended BRICS region. These developing themes demonstrate the research moving from basic investigations to developments in technology together with economic priorities (see Figure 10).

• 2005–2018 (Initial Period)

The basic concepts of “hydrogen”, “wind energy”, and “hydrogen production” defined this time period. The main emphasis during this research phase centered on learning the essential elements of hydrogen energy and wind power systems before advancing to later stages. Educational institutions and research organizations are developing “non-grid-connected” systems to explore decentralized renewable energy solutions for off-grid applications. These thematic elements proved to be dominant characteristics within this literature area since their Weighted Inclusion and Inclusion Indexes reached a maximum score of 1.00. These themes received little stability based on their low Stability Index because the research trends shifted after the study period.

• 2019–2023 (Expansion Period)

The research on renewable energy has established itself as the primary investigation focus by incorporating several sub-themes, including offshore wind power, hydrogen production, renewable energy sources, process design, and electrolysis. The research interest regarding “offshore wind power” has increased as scientists seek more effective methods to produce hydrogen using renewable wind resources, which follows ongoing global transitions toward renewable energy. Multiple research topics in this area demonstrated a high Occurrence Index of 22 because the field of study is rapidly expanding. Process design and electrolysis now appear as fundamental elements of the research devoted to technological aspects alongside engineering considerations of hydrogen production systems. Specialized studies about hydrogen generation process optimization began to replace broad renewable energy discussions during this period.

5.8.5. The Conceptual Structure Map Using the MCA Method

A Conceptual Structure Map within the Figure 11. demonstrates the connections between green hydrogen and renewable energy research keywords and the authors through MCA. The data accommodate 61.89% of its variance through Dim 1 at 37.64% and Dim 2 at 24.25%. Hydrogen production technologies form a separate dimension from renewable energy integration in the Conceptual Structure Map. The second dimension shows distinctions between energy efficiency, environmental matters, technical production aspects. Two major clusters emerge. The red polygon cluster comprises the research on hydrogen production along with utilization activities that stress the technical aspects of generating hydrogen under its main keywords: Hydrogen Production, Water Electrolysis, Energy Utilization, and Fuel Cells. This section comprises three parts that demonstrate sustainability and decarbonization: Renewable Energies together with Solar Energy and Carbon Dioxide. Economic Analysis accompanies Hydrogen Storage solutions to handle these respective problems. Hydrogen Production Utilization Sustainability serves as the most predominant subject.

The blue triangle cluster contains renewable energy sources and alternative application terms, including Green Hydrogen, Renewable Energy Resources, Fuel Cells, and Alternative Energy. The group focuses on renewable energy involvement in clean energy integration alongside green hydrogen development, as its thematic core is “Renewable Energy Sources and Green Hydrogen Development”. The two clusters connect through a direct link between renewable energy hydrogen production systems in the red cluster and sustainable renewable energy management in the blue cluster. Cross-dimensional terms like Economic Analysis bridge technical production with broader policy considerations. The map highlights two core objectives, which combine renewable power systems with hydrogen technologies through technical developments while promoting sustainable practices. Strategic developments will focus on improving renewable energy connections, cost optimization in hydrogen systems, broadening fuel cell capabilities, and reducing carbon emissions to fulfil hydrogen technology objectives.

6. Discussion

The bibliometric analysis of the green hydrogen and renewable energy research within the extended BRICS nations provides a structured understanding of the research field. This discussion responds to the key research questions by examining the trends in scientific production, the most influential sources, international collaboration, intellectual development, and the conceptual structure of the field.

R-Quest1: Evolution of Annual Scientific Production and Influence (2005–2024)

GH and RE research output has grown steadily between 2005 and 2024, with a notable surge after 2018. Early research between 2005 and 2012 largely focused on fundamental hydrogen production methods and renewable energy integration, as noted by [6]. The subsequent period (2013–2024) saw a transition towards applied investigations, including economic feasibility, policy frameworks, and electrolysis advancements [36]. This pattern aligns with the global shift toward decarbonization policies, which have fueled scientific and industrial interest in GH technologies. However, citation analysis highlights a fluctuating impact, with a peak in citations between 2015 and 2020, which can be attributed to major breakthroughs in hydrogen storage and utilization [8]. The declining trend in recent years suggests an increasing volume of publications leading to citation dispersion, a phenomenon observed in maturing research fields [23].

R-Quest2: Most Impactful, Prominent, and Dynamic Sources

The International Journal of Hydrogen Energy emerges as the most influential journal in the field, with a high total citation count and productivity, reflecting its pivotal role in advancing the hydrogen technology research [4]. Other impactful sources include Energy Conversion and Management and Renewable and Sustainable Energy Reviews, both of which have contributed significantly to studies on renewable integration and techno-economic evaluations of hydrogen production [13,16]. Additionally, Applied Energy and the Journal of Cleaner Production have provided substantial contributions to the economic and sustainability aspects of hydrogen energy, indicating an increasing interdisciplinary focus on the GH research [12]. The diversity of sources highlights a convergence of the technical, economic, and policy-driven research on green hydrogen and renewable energy within the extended BRICS region.

R-Quest3: Impact and Collaboration of Different Countries

China leads the GH and RE research in the extended BRICS group, both in terms of the output and impact, followed by India and Russia, reflecting their strong governmental and industrial commitments to hydrogen development [3]. India focuses on solar-based hydrogen production and electrolysis, while Russia’s contributions highlight the advances in hydrogen storage and hybrid energy systems [17]. South Africa and Brazil, though with less contributors, show a growing engagement in the hydrogen research, often in collaboration with global partners. International co-authorship rates stand at 25.68%, signifying a robust global collaboration, particularly between BRICS and European institutions [10]. The partnerships reflect the global urgency for hydrogen-based solutions and the role of BRICS nations in shaping the future of sustainable energy transitions.

R-Quest4: Intellectual Structure and Historiographic Evolution

The historiographic analysis identifies the key foundational works that have significantly influenced GH and RE research trajectories. Studies, such as [37], on water electrolysis [38], on bio-hydrogen production, and [38,39,40] on techno-economic assessments serve as major intellectual anchors in the field. Co-citation analysis reveals thematic clusters, primarily focused on hydrogen production technologies, economic feasibility studies, and policy frameworks [25]. The research has evolved from theoretical production models to applied solutions addressing commercialization and supply chain optimization [28]. Bibliographic coupling further indicates an interdisciplinary transition, linking the hydrogen research with sustainable development, climate change mitigation, and policy implementation [27]. This intellectual progression suggests a maturing research field with increasing real-world applicability and policy relevance.

R-Quest5: Conceptual Structure of the Research Field

The TreeMap visualization of the GH and RE research highlights “Hydrogen Production” as the dominant thematic area (23%), followed by “Renewable Energy” (16%) and “Water Electrolysis” (5%), reflecting the field’s emphasis on production methods and energy integration [6]. The three-field plot further establishes strong associations between leading research nations (China, India, and Iran), primary research themes (Hydrogen Production, Solar Energy, and Wind Power), and major publishing sources (International Journal of Hydrogen Energy, Energy Conversion and Management), confirming the interconnected nature of research productivity and knowledge dissemination [26].

Co-occurrence network analysis identifies three major research clusters. The Hydrogen Technologies and Applications cluster focuses on production, fuel cells, and storage solutions, reflecting industry-driven technological development [9]. The Advanced Hydrogen and Emerging Technologies cluster examines offshore wind-based hydrogen production, electrolysis advancements, and process optimization, showcasing the research priorities in increasing efficiency [15]. The Economic and Strategic Analysis cluster addresses financial feasibility, policy frameworks, and international hydrogen trade, demonstrating a shift toward market integration [22].

Thematic evolution analysis classifies green hydrogen and renewable energy research into three periods. The 2005−2012 phase focuses on early hydrogen production techniques, particularly non-grid wind power generation [18]. The 2013−2017 phase is an expansion into experimental technologies, such as biomass gasification and hybrid wind–solar hydrogen production [16]. The 2018−2024 period is characterized by a shift toward commercialization, supply chain optimization, and large-scale hydrogen integration within systems [20]. This evolution aligns with increasing industry participation and government policies supporting hydrogen economy development.

7. Conclusions

This research problem required a bibliometric investigation to study green hydrogen and renewable energy research developments in extended BRICS nations. The research into decarbonization and emerging economy contributions to global energy transformations requires a deep understanding of field development patterns and international partnerships and topics. This research study filled an important knowledge gap by creating maps of BRICS nations’ research publications about green hydrogen and renewable energy and analyzing their intellectual organization to develop strategic directions for future development.

This research shows that the green hydrogen and renewable energy investigation shows a steady expansion within the BRICS group after 2018, while China dominates in both research production and academic influence. Three main influential publications in the GH and RE research are the International Journal of Hydrogen Energy, Energy Conversion and Management, and Renewable and Sustainable Energy Reviews. Research collaborations primarily extend between BRICS institutions and their European counterparts. The research field on hydrogen production shifted from basic technical methods to add disciplinary applications, which focus on policy generation alongside economic validation and industrial use. The conceptual research directions concentrate on hydrogen production methods and electrolysis innovation as well as green hydrogen economic sustainability.

7.1. Discuss Implications

This research adds value to professional domains by conducting an extensive bibliometric evaluation of green hydrogen and renewable energy studies throughout BRICS economies. This study demonstrates the requirement for focused hydrogen technology investments as well as improved international sector collaborations and research agendas influenced by policy principles. BRICS nations continue their technological progress, which establishes them as leading stakeholders in the worldwide hydrogen economic framework. This research delivers valuable findings to help policymakers and stakeholders in funding agencies alongside industry leaders develop better energy transition approaches.

This research contains several limitations due to its extensive bibliometric method. The use of the Scopus database as an information source omits the research that appears in non-scoped journals together with regional research repositories. Malfunctions in bibliometric analysis generate useful quantitative data while lacking the capacity to measure policy effectiveness alongside the socioeconomic effects of adopting technologies for promotion. Additional research would benefit from including expert interviews as well as case studies to improve the bibliometric findings.

7.2. Future Research and Recommendation

Further research needs to evaluate the extended policy implications, which BRICS economies face due to their investments in green hydrogen and renewable energy development. Further insights into global energy transitions can be developed by performing a comparative analysis between the BRICS nations and other emerging economies. Environmental impact assessments and economic modeling methods combined with life cycle analyses will help professionals better evaluate the practicality of using GH. Research effectiveness would increase if studies delved into precise industrial sectors (such as transportation and heavy manufacturing) and their processes of transitioning to hydrogen-based energy systems.