Search Results (41)

The global energy landscape is transitioning towards cleaner solutions, with hydrogen emerging as a key energy source. To unlock hydrogen’s potential, it is crucial to prioritize the development of a more efficient, cost-effective, and environmentally friendly production process. Enhancing the efficiency and scalability of these technologies will not only reduce their environmental impact but also accelerate the adoption of hydrogen as a viable alternative energy solution, fostering a cleaner and more sustainable future. This paper presents a study on simulating a heat recovery system in an alkaline electrolyser consisting of 30 cells, which integrates a plate heat exchanger to preheat the water entering the system, and assessing how it affects efficiency. The study uses a thermal model, employing the concept of lumped thermal capacitance, to analyze the impact of the heat recovery system utilization on the overall performance of the electrolyser. MATLAB/Simulink was used to simulate and provide a detailed visualization of how recovery systems affect the electrolyser’s efficiency. The results of the simulations confirmed that incorporating a heat recovery system significantly improves the efficiency of alkaline electrolysers up to 8%. The study provides a promising outlook for the future of hydrogen production, emphasizing the potential of waste heat recovery systems to make green hydrogen production more viable and sustainable. Full article

Hydrogen is emerging as a key energy carrier in the transition to a low-carbon economy. This study reviews blue and green hydrogen, analysing their production technologies, environmental impacts, economic viability and global deployment trends. Blue hydrogen, derived from natural gas, coal or biomass with carbon capture, utilisation and storage, offers a transitional pathway by reducing emissions relative to unabated fossil routes, but its benefits depend on high CO₂ capture efficiencies and strict methane leakage control. Green hydrogen, produced via renewable-powered electrolysis and advanced thermochemical, photochemical and photoelectrochemical methods, represents the most sustainable long-term solution, though it is currently limited by cost and scale. This comparative assessment shows that green hydrogen’s production emissions, in the range of 0.67 kgCO-eq/kgH to 1.74 kgCO₂-eq/kgH₂, are substantially lower than those of blue hydrogen, in the range of 1.21 kgCO₂-eq/kgH₂ to 4.56 kgCO₂-eq/kgH₂, reinforcing its alignment with climate neutrality goals. Global production remains below 1% from low-emission sources, yet momentum is growing, with renewable-rich regions investing in large-scale electrolysers. A long short-term memory forecast suggests that blue hydrogen will dominate in the short term, but green hydrogen will surpass it around 2042. Together, both pathways are essential, blue hydrogen as a bridging option and green hydrogen as the foundation of a sustainable hydrogen economy. Full article

This paper compares national hydrogen (H₂) infrastructure plans in Canada, the United States (the USA), Singapore, and Sri Lanka, four countries with varying geographic and economic outlooks but shared targets for reaching net-zero emissions by 2050. It examines how each country approaches hydrogen production, pipeline infrastructure, policy incentives, and international collaboration. Canada focuses on large-scale hydrogen production utilizing natural resources and retrofitted natural gas pipelines supplemented by carbon capture technology. The USA promotes regional hydrogen hubs with federal investment and intersectoral collaboration. Singapore suggests an innovation-based, import-dominant strategy featuring hydrogen-compatible infrastructure in a land-constrained region. Sri Lanka maintains an import-facilitated, pilot-scale model facilitated by donor funding and foreign collaboration. This study identifies common challenges such as hydrogen embrittlement, leakages, and infrastructure scalability, as well as fundamental differences based on local conditions. Based on these findings, strategic frameworks are proposed, including scalability, adaptability, partnership, policy architecture, digitalization, and equity. The findings highlight the importance of localized hydrogen solutions, supported by strong international cooperation and international partnerships. Full article

In recent years, Co-based catalysts have attracted considerable attention in research on selective hydrogenation reactions because of their mild activities and favorable selectivities for producing intermediate products, especially in the selective hydrogenation of α,β-unsaturated aldehydes (UAL). However, the low activity of Co-based catalysts for activating hydrogen limits their application in industry, and the diversity of forms and electronic states of Co-based catalysts also leads to the development of complex products and hydrogenation mechanisms at Co active sites. This review provides a comprehensive and systematic overview of recent progress in the selective hydrogenation of UAL over Co-based catalysts, where the preparation methods, hydrogenation properties, and UAL hydrogenation mechanisms of Co-based catalysts are carefully discussed. The influences of nanosize effects, electronic effects, and coordination effects on Co metal and Co oxides are investigated. In addition, the different reaction mechanisms at Co active sites are compared, and their strengths and weaknesses for C=O hydrogenation are further proposed. Finally, the outlook and challenges for the future development of Co-based hydrogenation catalysts are highlighted. Full article

The growing demand for energy, coupled with the unsustainable nature of fossil fuels due to global warming and the greenhouse effect, have led to the advancement of renewable energy production concepts. Innovations such as photovoltaics, wind energy, and infrared energy harvesters are emerging as viable solutions. The challenge lies in the stochastic nature of renewable energy sources, which necessitates the implementation of electrical energy storage solutions, whether through batteries, supercapacitors, or hydrogen production. In this regard, innovative materials are essential to address the questions associated with these technologies. Metal-organic frameworks (MOFs) are crucial for achieving clean and efficient energy conversion in fuel cells and storage in batteries and supercapacitors. Metal-organic frameworks (MOFs) can be used as electrocatalytic materials, membranes for electrolytes, and energy storage materials. They exhibit exceptional design versatility, large surface, and can be functionalized with ligands with several charges and metallic centers. This article offers an in-depth examination of materials and devices utilizing metal-organic frameworks (MOFs) for electrochemical processes concerning the generation, transformation, and storage of electrical energy. This review specifically focuses on rechargeable batteries and fuel cells that incorporate MOFs. Finally, an outlook on the potential applications of MOFs in electrochemical industries is presented. Full article

The utilisation of fossil fuels has resulted in the continuous increase in anthropogenic carbon dioxide (CO₂) emissions and has led to significant environmental impacts. To this end, the catalytic hydrogenation of captured CO₂ into value-added C1 chemicals has attracted great attention. In this case, significant research efforts have been directed towards the development of heterogeneous catalysts. Owing to the unique properties and functionalities of hydridic hydrogen (H⁻), metal hydrides have shown great promise in hydrogen-involved catalytic processes. This is attributed to their enhanced hydrogen (H₂) absorption-desorption reversibility and newly developed active sites. Nevertheless, their application in the activation and hydrogenation of CO₂ has been overlooked. In this review paper, we provide an overview of recent advances in catalytic CO₂ hydrogenation using metal hydride-based materials. Firstly, the reaction mechanisms of CO₂ hydrogenation toward different C1 products (CO, CH₄, CH₃OH and HCOOH) are introduced to better understand their application trend. Thereafter, we highlight the challenges of developing robust hydride catalysts with different components and structures that enable tuning of their catalytic activity and selectivity. A brief introduction of the CO₂ hydrogenation over typical homogeneous metal hydrides complexes is also presented. Lastly, conclusion, future outlook and perspectives are discussed. Full article

The increasing demand for high-purity hydrogen (H₂) as renewable energy sources is driving advancements in membrane technology, which is essential for achieving efficient gas separation. Polyimide (PI) membranes have become an emerging option for H₂/CO₂ separation due to its excellent thermal stability and stability under harsh conditions. However, the neat PI membrane suffers performance loss due to CO₂ plasticization effect and an encountered trade-off limit between permeability and selectivity. Therefore, membrane modification by crosslinking and blending emerged as a recent strategy to enhance the membrane’s performance and properties. This paper provides: (1) An overview of the possible method to do the modification in PI membranes, including the advantages and challenges of the membrane modification types; (2) As blending and crosslinking is the most popular modification for the PI membrane, their roles in enhancing membrane properties for improved H₂/CO₂ separation are discussed; (3) The critical parameters of the blending and crosslinking processes are also clarified for the optimal purification process; (4) The future outlook for H₂/CO₂ separation using membrane technology is discussed, aiming to provide commercialization strategy for optimal H₂/CO₂ separation. Thus, this review could provide guidelines for the readers to implement changes that significantly enhance the membrane’s features for high-purity H₂ production. Full article

Life Cycle Assessment (LCA) methodology can be used to quantitatively assess the greenhouse gas emissions of low- or zero-carbon marine alternative fuels throughout their life cycle (from well to wake) and is an important basis for ensuring a green energy transition in the shipping industry. This paper first clarifies the trends and requirements of low-carbon development in shipping and introduces the major ship emission reduction technologies and evaluation methods. Next, the characteristics of various alternative marine fuels (i.e., LNG, hydrogen, methanol, ammonia, and biofuels) are comprehensively discussed and analyzed in terms of production, storage, transportation, and ship applications. In addition, this work provides a comprehensive overview of LCA methodology, including its relevant standards and assessment tools, and establishes a framework for LCA of marine alternative fuels. On this basis, a literature review of the current research on LCA of marine alternative fuels from the perspectives of carbon emissions, pollution emissions, and economics is presented. The case review covers 64 alternative-fueled ships and 12 groups of fleets operating in different countries and waters. Finally, this paper discusses the main shortcomings that exist in the current research and provides an outlook on the future development of LCA research of marine alternative fuels. Full article

Solar hydrogen production is a promising pathway for sustainable CO₂-free hydrogen production. It is mainly classified into three systems: photovoltaic electrolysis (PV-EC), photoelectrochemical (PEC) system, and particulate photocatalytic (PC) system. However, it still has trouble in commercialization due to the limitation of performance and economic feasibility in the large-scale system. In this review, the challenges of each large-scale system are, respectively, summarized. Based on this summary, recent approaches to solving these challenges are introduced, focusing on core components, fabrication processes, and systematic designs. In addition, several demonstrations of large-scale systems under outdoor conditions and performances of upscaled systems are introduced to understand the current technical level of solar-driven hydrogen production systems for commercialization. Finally, the future outlooks and perspectives on the practical application of large-scale solar-driven hydrogen production are discussed. Full article

This paper provides a comprehensive review and outlook on power converters devised for supplying polymer electrolyte membrane (PEM) electrolyzers from photovoltaic sources. The produced hydrogen, known as green hydrogen, is a promising solution to mitigate the dependence on fossil fuels. The main topologies of power conversion systems are discussed and classified; a loss analysis emphasizes the issues concerning the electrolyzer supply. The attention is focused on power converters of rated power up to a tenth of a kW, since it is a promising field for a short-term solution implementing green hydrogen production as a decentralized. It is also encouraged by the proliferation of relatively cheap photovoltaic low-power plants. The main converters proposed by the literature in the last few years and realized for practical applications are analyzed, highlighting their key characteristics and focusing on the parameters useful for designers. Future perspectives are addressed concerning the availability of new wide-bandgap devices and hard-to-abate sectors with reference to the whole conversion chain. Full article

Hydrogen production is one of the best solutions to the growing energy concerns, owing to its clean and sustainable assets. The current review gives an overview of various hydrogen production technologies, highlighting solar water splitting as a promising approach for its sustainable production. Moreover, it gives a detailed mechanism of the water-splitting reaction and describes the significance of titania-based catalysts for solar water splitting. It further highlights diversified strategies to improve the catalytic efficiency of TiO₂ for the enhanced hydrogen production. These strategies include the doping of TiO₂, dye sensitization, and the addition of co-catalysts. Doping reduces the bandgap by generating new energy levels in TiO₂ and encourages visible-light absorption. Sensitization with dyes tunes the electronic states, which in turn broadens the light-absorption capacity of titania. Constructing heterojunctions reduces the charge recombination of TiO₂, while co-catalysts increase the number of active sites for an enhanced reaction rate. Thus, every modification strategy has a positive impact on the stability and photocatalytic efficiency of TiO₂ for improved water splitting. Lastly, this review provides a comprehensive description and future outlook for developing efficient catalysts to enhance the hydrogen production rate, thereby fulfilling the energy needs of the industrial sector. Full article

The accumulation of organic dyes and heavy metals (HMs) in sewage sludge (SS) after wastewater treatment is a significant problem due to the non-degradable nature of these pollutants. Moreover, the simultaneous removal of HMs and dyes in the complex process of SS treatment, such as anaerobic digestion (AD), has become attractive. HMs and dyes present in SS can have a detrimental effect on anaerobic digesters. These pollutants not only inhibit the production of methane, which is crucial for biogas generation, but also affect the stability of AD treatment, which can result in failure or inadequate performance of the AD process. This review highlights a novel method of removing HMs and dyes from the AD process of SS through the use of biochar modified with polyvinyl alcohol (PVA) and chitosan (CTS). The applications of conventional biochar have been limited due to poor adsorption capacity. However, modification using PVA/CTS composites enhances properties such as surface functional groups, adsorption capacity, porosity, surface area selectivity, and stability. Furthermore, this modified version can function as an additive in AD of SS treatment to boost biogas production, which is a viable source for heat generation or electricity supply. In addition, the digestates can be further processed through plasma pyrolysis for the removal of HMs and dyes bound to the modified biochar. Plasma pyrolysis generates two major products: syngas and slag. The syngas produced can then be used as a source of hydrogen, heat, and electricity, while the slag can potentially be reused as an AD additive or as a biofertilizer in the agricultural sector. Additionally, this study addresses the challenges associated with this integration and biochar modifications, and offers an outlook on understanding the interactions between the modified biochar properties, microbial dynamics, and the presence of micropollutants to ensure the economic viability and scalability of this technology. This comprehensive review provides insights into the potential of PVA/CTS-modified biochar as an effective additive in AD systems, offering a sustainable approach to SS treatment and valuable resource recovery. Full article

Fermentation is an oxygen-free biological process that produces hydrogen, a clean, renewable energy source with the potential to power a low-carbon economy. Bibliometric analysis is crucial in academic research to evaluate scientific production, identify trends and contributors, and map the development of a field, providing valuable information to guide researchers and promote scientific innovation. This review provides an advanced bibliometric analysis and a future perspective on fermentation for hydrogen production. By searching WoS, we evaluated and refined 62,087 articles to 4493 articles. This allowed us to identify the most important journals, countries, institutions, and authors in the field. In addition, the ten most cited articles and the dominant research areas were identified. A keyword analysis revealed five research clusters that illustrate where research is progressing. The outlook indicates that a deeper understanding of microbiology and support from energy policy will drive the development of hydrogen from fermentation. Full article

Recently, worldwide, the attention being paid to hydrogen and its derivatives as alternative carbon-free (or low-carbon) options for the electricity sector, the transport sector, and the industry sector has increased. Several projects in the field of low-emission hydrogen production (particularly electrolysis-based green hydrogen) have either been constructed or analyzed for their feasibility. Despite the great ambitions announced by some nations with respect to becoming hubs for hydrogen production and export, some quantification of the levels at which hydrogen and its derived products are expected to penetrate the global energy system and its various demand sectors would be useful in order to judge the practicality and likelihood of these ambitions and future targets. The current study aims to summarize some of the expectations of the level at which hydrogen and its derivatives could spread into the global economy, under two possible future scenarios. The first future scenario corresponds to a business-as-usual (BAU) pathway, where the world proceeds with the same existing policies and targets related to emissions and low-carbon energy transition. This forms a lower bound for the level of the role of hydrogen and its penetration into the global energy system. The second future scenario corresponds to an emission-conscious pathway, where governments cooperate to implement the changes necessary to decarbonize the economy by 2050 in order to achieve net-zero emissions of carbon dioxide (carbon neutrality), and thus limit the rise in the global mean surface temperature to 1.5 °C by 2100 (compared to pre-industrial periods). This forms an upper bound for the level of the role of hydrogen and its penetration into the global energy system. The study utilizes the latest release of the annual comprehensive report WEO (World Energy Outlook—edition year 2023, the 26th edition) of the IEA (International Energy Agency), as well as the latest release of the annual comprehensive report WETO (World Energy Transitions Outlook—edition year 2023, the third edition) of the IRENA (International Renewable Energy Agency). For the IEA-WEO report, the business-as-usual situation is STEPS (Stated “Energy” Policies Scenario), and the emissions-conscious situation is NZE (Net-Zero Emissions by 2050). For the IRENA-WETO report, the business-as-usual situation is the PES (Planned Energy Scenario), and the emissions-conscious situation is the 1.5°C scenario. Through the results presented here, it becomes possible to infer a realistic range for the production and utilization of hydrogen and its derivatives in 2030 and 2050. In addition, the study enables the divergence between the models used in WEO and WETO to be estimated, by identifying the different predictions for similar variables under similar conditions. The study covers miscellaneous variables related to energy and emissions other than hydrogen, which are helpful in establishing a good view of how the world may look in 2030 and 2050. Some barriers (such as the uncompetitive levelized cost of electrolysis-based green hydrogen) and drivers (such as the German H2Global initiative) for the hydrogen economy are also discussed. The study finds that the large-scale utilization of hydrogen or its derivatives as a source of energy is highly uncertain, and it may be reached slowly, given more than two decades to mature. Despite this, electrolysis-based green hydrogen is expected to dominate the global hydrogen economy, with the annual global production of electrolysis-based green hydrogen expected to increase from 0 million tonnes in 2021 to between 22 million tonnes and 327 million tonnes (with electrolyzer capacity exceeding 5 terawatts) in 2050, depending on the commitment of policymakers toward decarbonization and energy transitions. Full article

Electrocatalytic and photocatalytic hydrogen evolution reactions (HERs) provide a promising approach to clean energy generation. Bimetallic single-atom catalysts have been developed and explored to be advanced catalysts for HER. It is urgent to review and summarize the recent advances in developing bimetallic single-atom HER catalysts. Firstly, the fundamentals of bimetallic single-atom catalysts are presented, highlighting their unique configuration of two isolated metal atoms on their supports and resultant synergistic effects. Secondly, recent advances in bimetallic single-atom catalysts for electrocatalytic HER under acidic/alkaline conditions are then reviewed, including W-Mo, Ru-Bi, Ni-Fe, Co-Ag, and other dual-atom systems on graphene and transition metal dichalcogenides (TMDs) with enhanced HER activity versus monometallic analogs due to geometric and electronic synergies. Then, photocatalytic bimetallic single-atom catalysts on semiconducting carbon nitrides for solar H₂ production are also discussed. Finally, an outlook is provided on opportunities and challenges in precisely controlling bimetallic single-atom catalyst synthesis and gaining in-depth mechanistic insights into bimetallic interactions. Further mechanistic and synthetic studies on bimetallic single-atom catalysts will be imperative for developing optimal systems for efficient and sustainable hydrogen production. Full article