Hydrogen

Creating a hydrogen market in Africa is a great opportunity to assist in the promotion of sustainable energy solutions and economic growth. This article addresses the legislation and regulations that need to be developed to facilitate growth in the hydrogen market and allow local green hydrogen offtake across the continent. By reviewing current policy and strategy within particular African countries and best practices globally from key hydrogen economies, the review establishes compelling issues, challenges, and opportunities unique to Africa. The study identifies the immense potential in Africa for renewable energy, and, in particular, for solar and wind, as the foundation for the production of green hydrogen. It examines how effective policy frameworks can establish a vibrant hydrogen economy by bridging infrastructural gaps, cost hurdles, and regulatory barriers. The paper also addresses how local offtake contracts for green hydrogen can be used to stimulate economic diversification, energy security, and sustainable development. Policy advice is provided to assist African authorities and stakeholders in the deployment of enabling regulatory frameworks and the mobilization of funds. The paper contributes to global hydrogen energy discussions by introducing Africa as an eligible stakeholder in the emerging hydrogen economy and outlining prospects for its inclusion into regional and global energy supply chains. Full article

Research on and the demand for hydrogen-powered vehicles have grown significantly over the past two decades as a solution for sustainable transportation. Bibliometric analysis helps to assess research trends, key contributions, and the impact of studies focused on the safety and reliability of hydrogen-powered vehicles. This study provides a novel methodology for bibliometric analysis that systematically evaluates the global research landscape on hydrogen-powered vehicle reliability using Scopus-indexed publication data (1965 to 2024). Eighteen key parameters were identified for this study that are often used by researchers for the bibliometric analysis of hydrogen-related studies. Data analytics, VOSviewer-based visualization, and research impact indicators were integrated to comprehensively assess publication trends, key contributors, and citation networks. The analysis revealed that hydrogen-powered vehicle reliability research has experienced significant growth over the past two decades, with leading contributions from high-impact journals, renowned institutions, and influential authors. The present study emphasizes the significance of greater funding as well as open-access distribution. Furthermore, while major worldwide institutions have significant institutional relationships, there are gaps in real-world hydrogen infrastructure evaluations, large-scale experimental validation, and policy-driven research. Full article

This article examines hydrogen production using Proton Exchange Membrane Electrolyzers (PEMELs) and photovoltaic (PV) panels using Maximum Power Point Tracking (MPPT). This method has great potential to maximize the production of pure hydrogen, making it possible to reduce and potentially eliminate the difficulties associated with sudden drops and interruptions in output power. The use of MPPT algorithms in conjunction with Direct Current to Direct Current (DC/DC) converters helps improve the energy efficiency of systems. This study aims to enhance green hydrogen production by optimizing PV-PEMEL performance using commercial power electronics, while improving energy storage and reducing costs for sustainable hydrogen generation. Full article

As the attention to using hydrogen as a potential energy storage medium for power generation and mobility increases, hydrogen production, storage, and transportation safety should be considered. For instance, hydrogen’s extreme physical and chemical properties and the wide range of flammable concentrations raise many concerns about the current safety measures in processing other flammable gases. Hydrogen cloud accumulation in the case of leakage in confined spaces can lead to reaching the hydrogen lower flammability limit (LFL) within seconds if the hydrogen is not properly evacuated from the space. At Jülich Research Centre, hydrogen mixed with natural gas is foreseen to be used as a fuel for the central heating system of the campus. In this work, the release, dispersion, formation, and spread of the hydrogen cloud in the case of hydrogen leakage inside the central utility building of the campus are numerically simulated using the OpenFOAM-based containmentFOAM CFD codes. Additionally, different ventilation scenarios are simulated to investigate the behavior of the hydrogen cloud. The results show that locating exhaust openings close to the ceiling and the potential leakage source can be the most effective way to safely evacuate hydrogen from the building. Additionally, locating the exhaust outlets near the ceiling can decrease the combustible cloud volume by more than 25% compared to side openings far below the ceiling. Also, hydrogen concentrations can reach the LFL in case of improper forced ventilation after only 8 s, while it does not exceed 0.15% in the case of natural ventilation under certain conditions. The results of this work show the significant effect of locating exhaust outlets near the ceiling and the importance of natural ventilation to mitigate the effects of hydrogen leakage. The approach illustrated in this study can be used to study hydrogen dispersion in closed buildings in case of leakage and the proper design of the ventilation outlets for closed spaces with hydrogen systems. Full article

Hydrogen atom transfer (HAT), a concerted charge transfer involving two elementary particles, a proton and an electron, plays a key role in many areas of chemistry and biochemistry. A molecular dynamics study based on density functional theory was performed to investigate the reaction mechanism of hydrogen atom transfer from quercetin anions to the hydroxyl radical in a neutral aqueous media. Intrinsic bond orbital (IBO) analysis of a series of structures obtained from trajectories was performed in simulations in which the reaction occurred, and the electron flow along the reaction coordinate was determined and applied to investigate the reaction mechanism. The reaction in the simulations proceeded rapidly as proton-coupled electron transfer (PCET) or electron transfer–proton transfer (ET-PT) depending on the initial position and solvation of the reactants. Full article

We investigated experimentally the influence of flow conditions and electrode position on a diffusion H₂–air flame subjected to an external electric field. We determined the minimum impurity level required to observe changes in flame properties with applied voltage. Flame OH chemiluminescence signals were recorded using a UV-sensitive CCD array as a function of voltage (+10 to −10 kV) applied to a stainless-steel ring electrode placed around the burner nozzle. Changes in chemiluminescence signals are reported as a function of electrode height above the burner, airflow, and fuel composition. Significant changes in OH* distributions were observed for voltages below −5 kV. Under optimum conditions, the height of the chemiluminescence flame decreased by up to 67% at the maximum applied voltage. The flame transitioned from a teardrop shape to a flat, open-tip flame at a voltage corresponding to an inflection point in the flame height–voltage profiles. Increasing the airflow rate shifted the inflection point to more negative values until almost suppressing the effect of the electric field on the flame structure. This study reveals that carbon impurities in hydrogen fuel as low as 10 ppm are sufficient to observe significant effects from external electric fields without changing the underlying neutral chemistry. We also determine the set of parameters that control the amplitude of the structural change. Full article

To pursue the total decarbonization goal set at 2050, the introduction of hydrogen to replace the usage of fossil fuel in hard-to-abate industrial sectors is crucial. Hydrogen will replace natural gas in hard-to-abate sectors where natural gas is required to make heat necessary for the industrial process. Naturally, all this is worthwhile if hydrogen is produced following a green pathway, meaning that it is connected with renewable sources. In this manuscript, a techno-economic analysis related to a real case scenario is carried out. The real system addressed involves continuous high-temperature industrial furnace operation with a seasonally variable but stable thermal energy demand, representing typical conditions of hard-to-abate industrial processes. Solar photovoltaic panels combined with batteries are used to generate and store electricity that in turn is used to generate green hydrogen. Different scenarios are considered, including mixed natural gas/hydrogen, the seasonal variability of industrial needs, and the variability of solar production. The economic aspects considered include the usage of anion exchange membrane water electrolyzers (AEMWEs) to produce green hydrogen, the improvement in efficiency during operations (operational costs, OPEX), and the decrease in the AEMWE cost (Capital expenditures, CAPEX) that occur over time. The study shows that the hydrogen production cost could decrease from 12.6 EUR kg⁻¹ in 2024 to 9.7 EUR kg⁻¹ in 2030, with further reduction to 8.7 EUR kg⁻¹ achievable through seasonal blending strategies. CO₂ emissions are significantly reduced through partial displacement of natural gas with green hydrogen, highlighting the environmental potential of the system. Full article

The gasification of cellulose typically requires high temperatures (>600 °C) due to the thermal stability of levoglucosan, a major intermediate formed during pyrolysis. In this study, we investigated the gasification behavior of cellulose by combining infrared (IR) heating with low-power dielectric barrier discharge (DBD) plasma treatment. Cellulose filter paper was first pyrolyzed using localized IR irradiation (2 kW for 30 s), generating mist-like volatile products including levoglucosan. These volatiles were then exposed to DBD plasma (16–64 W for 1 or 3 min) under Ar flow. Despite the relatively low estimated gas temperatures below 240 °C in the plasma region, gas yields, including H₂ and CO, increased markedly with discharge power, reaching up to 72.6 wt% at 64 W for 3 min—more than four times that obtained with IR heating alone. These results indicate that DBD plasma facilitates the gasification of pyrolysis volatiles under significantly lower temperature conditions than those required in conventional thermal gasification. This approach may offer a route toward low-temperature biomass gasification with reduced tar, coke, and clinker formation. Full article

The hydrogen fuel quality is critical to the efficiency and longevity of fuel cell electric vehicles (FCEVs), with ISO 14687:2019 grade D establishing stringent impurity limits. This study compared two different sampling techniques for assessing the hydrogen fuel quality, focusing on the National Physical Laboratory hydrogen direct sampling apparatus (NPL DirSAM) from a 35 MPa heavy-duty (HD) dispenser and qualitizer sampling from a 70 MPa light-duty (LD) nozzle, both of which were deployed on the same day at a local hydrogen refuelling station (HRS). The collected samples were analysed as per the ISO 14687:2019 contaminants using the NPL H₂-quality laboratory. The NPL DirSAM was able to sample an HD HRS, demonstrating the ability to realise such sampling on an HD nozzle. The comparison of the LD (H₂ Qualitizer sampling) and HD (NPL DirSAM) devices showed good agreement but significant variation, especially for sulphur compounds, non-methane hydrocarbons and carbon dioxide. These variations may be related to the HRS difference between the LD and HD devices (e.g., flow path, refuelling conditions and precooling for light duty versus no precooling for heavy duty). Further study of HD and LD H₂ fuel at HRSs is needed for a better understanding. Full article

The hydrogen (H₂) economy is seen as a crucial pathway for decarbonizing the energy system, with green H₂—i.e., obtained from water electrolysis supplied by renewable energy—playing a key role as an energy carrier in this transition. The growing interest in H₂ comes from its versatility, which means that H₂ can serve as a raw material or energy source, and various technologies allow it to be produced from a wide range of resources. Environmental impacts of H₂ production have primarily focused on greenhouse gas (GHG) emissions, despite other environmental aspects being equally relevant in the context of a sustainable energy transition. In this context, Life Cycle Assessment (LCA) studies of H₂ supply chains have become more common. This paper aims to compile and analyze discrepancies and convergences among recent reported values from 42 scientific studies related to different H₂ production pathways. Technologies related to H₂ transportation, storage and use were not investigated in this study. Three environmental indicators were considered: Global Warming Potential (GWP), Energy Performance (EP), and Water Consumption (WF), from an LCA perspective. The review showed that H₂ based on wind, photovoltaic and biomass energy sources are a promising option since it provides lower GWP, and higher EP compared to conventional fossil H₂ pathways. However, WF can be higher for H₂ derived from biomass. LCA boundaries and methodological choices have a great influence on the environmental indicators assessed in this paper which leads to great variability in WF results as well as GWP variation due credits given to avoid GHG emissions in upstream process. In the case of EI, the inclusion of energy embodied in renewable energy systems demonstrates great influence of upstream phase for electrolytic H₂ based on wind and photovoltaic electricity. Full article

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. Full article

International projects study the safety aspects of the storage and long-distance transportation of liquid hydrogen at large scales. Catalytic recombiners, which are today key elements of hydrogen risk mitigation in nuclear power plants, could become an efficient safety device to prevent flammable gas mixtures after liquid hydrogen leakages in closed rooms. This study tackles fundamental questions about the operational behavior of typical recombiner catalysts related to the conditions of the start-up and the termination of the catalytic reaction. For this purpose, small-scale catalyst sheets with coatings containing either platinum or palladium as active materials were exposed to gas mixtures of air and hydrogen of up to 4 vol.% at temperatures between −50 °C and 20 °C. Both platinum and palladium showed variation to performance and had stochastic results. Overall, the initialized platinum catalyst was better than the palladium. The experimental results show that the transfer of the recombiner technology from its current application is not easily possible. Full article

Hydrogen and some of its derivatives (such as e-methanol, e-methane, and e-ammonia) are promising energy carriers that have the potential to replace conventional fuels, thereby eliminating their harmful environmental impacts. An innovative use of hydrogen as a zero-emission fuel is forming weakly ionized plasma by seeding the combustion products of hydrogen with a small amount of an alkali metal vapor (cesium or potassium). This formed plasma can be used as a working fluid in supersonic open-cycle magnetohydrodynamic (OCMHD) power generators. In these OCMHD generators, direct-current (DC) electricity is generated straightforwardly without rotary turbogenerators. In the current study, we quantitatively and qualitatively explore the levels of electric conductivity and the resultant volumetric electric output power density in a typical OCMHD supersonic channel, where thermal equilibrium plasma is accelerated at a Mach number of two (Mach 2) while being subject to a strong applied magnetic field (applied magnetic-field flux density) of five teslas (5 T), and a temperature of 2300 K (2026.85 °C). We varied the total pressure of the pre-ionization seeded gas mixture between 1/16 atm and 16 atm. We also varied the seed level between 0.0625% and 16% (pre-ionization mole fraction). We also varied the seed type between cesium and potassium. We also varied the oxidizer type between air (oxygen–nitrogen mixture, 21–79% by mole) and pure oxygen. Our results suggest that the ideal power density can reach exceptional levels beyond 1000 MW/m³ (or 1 kW/cm³) provided that the total absolute pressure can be reduced to about 0.1 atm only and cesium is used for seeding rather than potassium. Under atmospheric air–hydrogen combustion (1 atm total absolute pressure) and 1% mole fraction of seed alkali metal vapor, the theoretical volumetric power density is 410.828 MW/m³ in the case of cesium and 104.486 MW/m³ in the case of potassium. The power density can be enhanced using any of the following techniques: (1) reducing the total pressure, (2) using cesium instead of potassium for seeding, and (3) using air instead of oxygen as an oxidizer (if the temperature is unchanged). A seed level between 1% and 4% (pre-ionization mole fraction) is recommended. Much lower or much higher seed levels may harm the OCMHD performance. The seed level that maximizes the electric power is not necessarily the same seed level that maximizes the electric conductivity, and this is due to additional thermochemical changes caused by the additive seed. For example, in the case of potassium seeding and air combustion, the electric conductivity is maximized with about 6% seed mole fraction, while the output power is maximized at a lower potassium level of about 5%. We also present a comprehensive set of computed thermochemical properties of the seeded combustion gases, such as the molecular weight and the speed of sound. Full article

A novel design of a proton exchange membrane electrolyzer is presented. In contrast to previous designs, the flow field plates are round and oriented horizontally with the feed water entering from a central hole and spreading evenly outward over the anode flow field in radial, interdigitated flow channels. The cathode flow field consists of a spiral channel with an outlet hole near the outside of the bipolar plate. This results in anode and cathode flow channels that run perpendicular to avoid shear stresses. The novel sealing concept requires only o-rings, which press against the electrolyte membrane and are countered by circular gaskets that are placed over the flow channels to prevent the membrane from penetrating the channels, which makes for a much more economical sealing concept compared to prior designs using custom-made gaskets. Hydrogen leaves the electrolyzer through a vertical outward pipe placed off-center on top of the electrolyzer. The electrolyzer stack is housed in a cylinder to capture the oxygen and water vapor, which is then guided into a heat exchanger section, located underneath the electrolyzer partition. The function of the heat exchanger is to preheat the incoming fresh water and condense the escape water, thus improving the efficiency. It also serves as internal phase separator in that a level sensor controls the water level and triggers a recirculation pump for the condensate, while the oxygen outlet is located above the water level and can be connected to a vacuum pump to allow for electrolyzer operation at sub-ambient pressure to further increase efficiency and/or reduce the iridium loading. Full article

Green hydrogen is gaining recognition as a viable substitute for fossil fuels, presenting a sustainable solution for global decarbonization. While significant progress has been made in hydrogen production, storage, and utilization, there remains a crucial need to assess its economic viability and integration into current energy systems and to reduce its emission footprint. This review delves into the prospects and challenges of green hydrogen deployment into the renewable energy mix, with a particular focus on cost reduction approaches, storage limitations, transportation, scalability, advancements in electrolysis, and diverse sectoral applications. By analyzing recent technological developments and policy frameworks, this review contributes a thorough evaluation of green hydrogen’s viability to achieve net-zero emissions. Furthermore, this review enhances understanding of the role of green hydrogen in climate change mitigation by identifying major scalability barriers and proffering actionable solutions, assessing life cycle emission reductions, and examining key policy measures required for large-scale adoption. Our analysis emphasizes the importance of advancing green hydrogen storage solutions, increasing the efficiency of electrolysis processes, reducing costs, and implementing stronger policy measures to support large-scale adoption. Our findings and results demonstrate that green hydrogen has 66–95% potential of reducing global warming when integrated with other renewables. Its widespread adoption will drastically reduce anticipated climate mitigation costs of $10.0–15.7 trillion in the next decades, with progress in electrolysis technology, cost efficiency, and various industrial applications. Our recommendation for future studies emphasizes improved catalyst durability, material enhancements for electrolyzer, integration of green hydrogen into hybrid renewable energy networks, and establishment of globally coordinated policies to accelerate its deployment. By bridging the divide between technological advancements and practical implementation, this research provides valuable guidance for scientists, policymakers, and industry stakeholders striving for a sustainable energy transition. Full article

This paper provides a system-level and dimensional analysis of green hydrogen, assessing its realistic deployment potential within broader energy transitions. While green hydrogen—produced via electrolysis using renewable electricity—is often promoted as a versatile decarbonization solution for industry, mobility, and civil applications, its practical implementation is constrained by high energy consumption, conversion inefficiencies, and complex supply chain requirements. This study highlights typical energy demands across key sectors and evaluates the scale of the renewable infrastructure needed to support them, offering quantitative insight into the feasibility of large-scale hydrogen integration. It also reflects current technological maturity, noting that many promising solutions remain far from industrial readiness. Finally, the paper underscores the importance of targeted policies and bankable investment models to foster the development of hydrogen ecosystems, emphasizing that its role should be framed within a selective, evidence-based strategy that focuses on high-impact applications. The analysis identifies key dimensional challenges, including the magnitude of renewable energy capacities required for sector-wide hydrogen integration and the scale of infrastructure investments needed to bridge current gaps. Full article

This study comparatively evaluates the performance of ABO₃ perovskite materials (A = La, Ca, Sr; B = Mn, Fe) as oxygen carriers in three-step Chemical Looping Hydrogen (CLH) technology, focusing on redox behavior, oxygen transport capacity, hydrogen production, and selectivity under controlled pulse-mode conditions. The redox behavior of the materials is analyzed in relation to their defect chemistry. Perovskites such as (La_1−xCa_x)MnO₃, (La_1−xSr_x)MnO₃, and (La_0.6Ca_0.4)(Mn_1−xFe_x)O₃ were synthesized via wet chemical methods and tested in chemical looping cycles. Doping A-site cations with Ca or Sr enhanced oxygen delivery capacity by more than 100% upon reduction with CH₄ when dopant content (x) increased from 0 to 0.5. However, H₂ selectivity decreased from 52% to 2.5% for (La_1−xCa_x)MnO₃ and from 46% to 14% for (La_1−xSr_x)MnO₃ under the same conditions. In contrast, substituting Mn with Fe significantly improved hydrogen production, particularly in LaFeO₃, which exhibited the highest hydrogen selectivity and yield. At 1000 °C, LaFeO₃ produced nearly 10 mmol H₂ g⁻¹, with 80% generated during the reduction step at 99.9% selectivity and the remaining 20% during the water-splitting step at 100% selectivity. These results are linked to the extent of B-site cation reduction reactions (i) B⁴⁺ → B³⁺, which facilitates complete fuel oxidation and (ii) B³⁺ → B²⁺, which leads to partial fuel oxidation. The reverse of (ii) also contributes to H₂ production during water splitting. Additionally, the study assesses the materials’ microstructure and stability over prolonged cycles. The findings highlight Fe-based perovskites, particularly LaFeO₃, as promising candidates for CLH applications, emphasizing the need for structural and compositional optimization to enhance hydrogen production efficiency. Full article

As hydrogen emerges as a pivotal energy carrier in the global transition towards net-zero emissions, addressing its technological and regulatory challenges is essential for large-scale deployment. The widespread adoption of hydrogen technologies requires extensive research, technical advancements, validation, testing, and certification to ensure their efficiency, reliability, and safety across various applications, including industrial processes, power generation, and transportation. This study provides an overview of key enabling technologies for green hydrogen production and distribution, highlighting the critical challenges that must be overcome to facilitate their widespread adoption. It examines key hydrogen use cases across multiple sectors, analysing their associated technical and infrastructural challenges. The technological advancements required to improve hydrogen production, storage, transportation, and end-use applications are discussed. The development of state-of-the-art testing and validation facilities is also assessed, as these are vital for ensuring safety, performance, and regulatory compliance. This work also reviews some of the ongoing academic and industrial initiatives in the UK aimed at promoting technological innovation, advancing hydrogen expertise, and developing world-class testing infrastructures. This study emphasises the need for stronger, more integrated collaboration between universities, industries, and certifying bodies for building a strong network that promotes knowledge sharing, standardisation, and innovation for expanding hydrogen solutions and creating a sustainable hydrogen economy. Full article

Acoustic oscillations in cryogenic systems can either be imposed intentionally, as in pulse-tube cryocoolers, or occur spontaneously due to Taconis-type thermoacoustic instabilities. To predict the propagation of sound waves in ducts with sudden changes in cross-sectional areas, minor losses associated with such transitions in oscillatory flows must be known. However, the current modeling approaches usually rely on correlations for minor loss coefficients obtained in steady flows, which may not accurately represent minor losses in sound waves. In this study, high-fidelity computational fluid dynamics simulations are undertaken for acoustic oscillations at transitions between tubes of different diameters filled with cryogenic hydrogen. The variable parameters include the tube diameter ratios, temperatures (80 K and 30 K), and acoustic impedances corresponding to standing and traveling waves. Computational simulation results are compared with reduced-order acoustic models to develop corrections for minor loss coefficients that describe transition losses in sound waves more precisely. The present findings can improve the accuracy of design calculations for acoustic cryocoolers and predictions of Taconis instabilities. Full article