Production & Supply Chain

Dark fermentation (DF) has gained increasing interest over the past two decades as a sustainable route for biohydrogen production; however understanding how reproducible the process can be both from macro- and microbiological perspectives remains limited. This study assessed the reproducibility of a parallel continuous DF system using fruit-vegetable waste as a substrate under strictly controlled operational conditions. Three stirred-tank reactors were operated in parallel for 90 days monitoring key process performance indicators. In addition to baseline operation different process enhancement strategies were tested including bioaugmentation supplementation with nutrients and/or additional fermentable carbohydrates and modification of key operational parameters such as pH and hydraulic retention time all widely used in the field to improve DF performance. Microbial community structure was also analyzed to evaluate its reproducibility and potential relationship with process performance and metabolic patterns. Under these conditions key performance indicators and core microbial features were reproducible to a large extent yet full consistency across reactors was not achieved. During operation unforeseen operational issues such as feed line clogging pH control failures and mixing interruptions were encountered. Despite these disturbances the system maintained an average hydrogen productivity of 3.2 NL H2/L-d with peak values exceeding 6 NL H2/L-d under optimal conditions. The dominant microbial core included Bacteroides Lactobacillus Veillonella Enterococcus Eubacterium and Clostridium though their relative abundances varied notably over time and between reactors. An inverse correlation was observed between lactate concentration in the fermentation broth and the amount of hydrogen produced suggesting it can serve as a precursor for hydrogen. Overall the findings presented here demonstrate that DF processes can be resilient and broadly reproducible. However they also emphasize the sensitivity of these processes to operational disturbances and microbial shifts. This underscores the necessity for refined control strategies and further systematic research to translate these insights into stable high-performance real-world systems.

Water electrolyzers play a crucial role in green hydrogen production. However their efficiency and scalability are often compromised by bubble dynamics across various scales from nanoscale to macroscale components. This review explores multi-scale modeling as a tool to visualize multi-phase flow and improve mass transport in water electrolyzers. At the nanoscale molecular dynamics (MD) simulations reveal how electrode surface features and wettability influence nanobubble nucleation and stability. Moving to the mesoscale models such as volume of fluid (VOF) and lattice Boltzmann method (LBM) shed light on bubble transport in porous transport layers (PTLs). These insights inform innovative designs including gradient porosity and hydrophilic-hydrophobic patterning aimed at minimizing gas saturation. At the macroscale VOF simulations elucidate two-phase flow regimes within channels showing how flow field geometry and wettability affect bubble discharging. Moreover artificial intelligence (AI)-driven surrogate models expedite the optimization process allowing for rapid exploration of structural parameters in channel-rib flow fields and porous flow field designs. By integrating these approaches we can bridge theoretical insights with experimental validation ultimately enhancing water electrolyzer performance reducing costs and advancing affordable highefficiency hydrogen production.

The paper investigates the potential of co-electrolysis as a viable pathway for hydrogen production and industrial decarbonization expanding on previous studies on water electrolysis. The analysis adopts a general and critical perspective aiming to assess the realistic scope of this technology with regard to current energy and environmental needs. Although co-electrolysis theoretically offers improved efficiency by simultaneously converting H2O and CO2 into syngas the practical advantages are difficult to consolidate. The study highlights that the energetic margins of the process remain relatively narrow and that several key aspects including system irreversibility and the limited availability of CO2 in many contexts significantly constrain its applicability. Despite the growing interest and promising technological developments co-electrolysis still faces substantial challenges before it can be implemented on a larger scale. The findings suggest that its success will depend on targeted integration strategies advanced thermal management and favorable boundary conditions rather than on the intrinsic efficiency of the process alone. However there are specific sectors where assessing the implementation potential of co-electrolysis could be of interest a perspective this paper aims to explore.

The current study evaluates the feasibility of a forward osmosis membrane bioreactor (FO-MBR) for dark fermentation aiming at simultaneous biohydrogen production and wastewater treatment. Optimal microbial inoculation was achieved via heat-treated activated sludge enriching Clostridium sensu stricto 1 and yielding up to 2.21 mol H2.(mol hexose)− 1 in batch mode. In continuous operation a substrate concentration of 4.4 g L− 1 and a hydraulic retention time (HRT) of 12 h delivered the best results producing 1.51 mol H2.(mol hexosesupplied) − 1 . The FO-MBR configured with a 1.1 m2 hollow fiber side-stream membrane module and operated under dynamic HRT (2.5–12 h) dependent on membrane flux was integrated with intermittent CSTR (Continuous stirred tank reactor) operation to counter metabolite accumulation. This system outperformed a conventional CSTR achieving a hydrogen yield of 1.78 mol H2.(mol hexosesupplied) − 1 . Remarkable treatment efficiencies were observed with BOD5 COD and TOC removal rates of 95.32 % 99.02 % and 99.10 % respectively and an 83.8 % reduction in total waste volume. Additionally the FO-MBR demonstrated strong antifouling performance with 96.14 % water flux recovery achieved after a brief 5 min hydraulic rinse following 47.5 h of continuous highstrength broth exposure. These results highlight the FO-MBR system’s ability as a sustainable and highperformance alternative for integrated hydrogen production and effluent treatment. Further studies are recommended to address long-term fouling control and metabolite management for industrial scalability.

Photoelectrochemical (PEC) water splitting is a promising technology for green hydrogen production by harnessing solar energy. Traditionally this sustainable approach is studied under light intensity of 100 mW/cm2 mimicking the natural solar irradiation at the Earth’s surface. Sunlight can be easily concentrated using simple optical systems like Fresnel lens to enhance charge carrier generation and hydrogen production in PEC water splitting. Despite the great potentials this strategy has not been extensively studied and faces challenges related to the stability of photoelectrodes. To prompt the investigations and applications this work outlines the best practices and protocols for conducting PEC solar water splitting under concentrated sunlight illumination incorporating our recent advancements and providing some experimental guidelines. The key factors such as light source calibration photoelectrode preparation PEC cell configuration and long-term stability test are discussed to ensure reproducible and high performance. Additionally the challenges of the expected photothermal effect and the heat energy utilization strategy are discussed.

This study focuses on enhancing the efficiency of alkaline water electrolysis technology a key process in green hydrogen production by leveraging the synergy of magnetic fields and in situ electrode activation. Optimizing AWE efficiency is essential to meet increasing demands for sustainable energy solutions. In this research nickel mesh electrodes were modified through the application of magnetic fields and the addition of hypo-hyper d-metal (cobalt complexes and molybdenum salt) to the electrolyte. These enhancements improve mass transfer facilitate bubble detachment and create a high-surface-area catalytic layer on the electrodes all of which lead to improved hydrogen evolution rates. The integration of magnetic fields and in situ activation achieved over 35% energy savings offering a cost-effective and scalable pathway for industrial green hydrogen production.

This review investigates hydrogen production via photocatalysis using ammonia a carbon-free source potentially present in wastewater. Photocatalysis offers low energy requirements and high conversion efficiency compared to electrocatalysis thermocatalysis and plasma catalysis. However challenges such as complex material synthesis low stability spectral inefficiency high costs and integration barriers hinder industrial scalability. The review addresses thermodynamic requirements reaction mechanisms and the role of pH in optimizing photocatalysis. By leveraging ammonia’s potential and advancing photocatalyst development this study provides a framework for scalable sustainable hydrogen production and simultaneous ammonia decomposition paving the way for innovative energy solutions and wastewater management.

This study offers a novel techno-economic evaluation of a small hydrogen generation system included into a residential villa in Sharjah. The system is designed to utilize solar energy for hydrogen production using an electrolyzer. The study assesses two scenarios: one lacking a fuel cell and the other incorporating a fuel cell stack for backup power. The initial scenario employs a solar-powered electrolyzer for hydrogen production attaining a competitive levelized cost of energy (LCOE) of $0.1846 per kWh and a hydrogen cost of $4.65 per kg. These data underscore the economic viability of utilizing electrolyzers for hydrogen generation. The system produces around 1230 kg of hydrogen per annum rendering it appropriate for many uses. Nevertheless the original investment expenditure of $73980 necessitates more optimization. The second scenario includes a 10 kW fuel cell for energy autonomy. This scenario has a marginally reduced LCOE of 0.1811 $/kWh and a cumulative net present cost of $72600. The fuel cell runs largely at night proving the efficiency of the downsizing option in decreasing capital expense. The system generates electricity from solar panels (66.1 MWh/year) and the fuel cell (16.9 MWh/year) exhibiting a multi-source power generating technique. The results indicate that scaled-down hydrogen generation systems both with and without fuel cells may offer sustainable and possibly lucrative renewable energy options for household use especially in areas with ample solar resources such as Sharjah.

Green hydrogen (GH2) a sustainable and clean energy carrier is increasingly regarded as a solution to energy challenges and environmental issues. Industrial wastewater possesses a significant potential for hydrogen generation using biological chemical and electrochemical methods. This review analysis evaluates progress in GH2 production from industrial wastewater highlighting its environmental and cost benefits. Process optimization technological improvements and enhancements in catalysts for chemical and electrochemical hydrogen generation are also provided. It also considers the integration of GH2 production methods with wastewater treatment procedures to achieve synergistic benefits including enhanced pollutant removal and energy recovery. Challenges associated with GH2 production include substrate variability economic viability reactor scalability and environmental sustainability are also discussed. Also this review provides a future outlook to promote sustainable energy solutions and tackle global environmental issues related to GH2 from industrial wastewater.

This study investigates the integration of multiple energy carriers within a unified multi-carrier energy system using an energy cascade approach. The system harnesses geothermal energy to power interconnected subsystems including an organic Rankine cycle (ORC) liquefied natural gas (LNG) and a solid oxide fuel cell (SOFC) stack. The dual ORC system and LNG stream are directly fed from the geothermal source while the SOFC stack uses methane produced during LNG regasification. Besides electricity the system generates hydrogen and desalinated water by incorporating a proton exchange membrane (PEM) electrolyzer and a reverse osmosis (RO) desalination plant. The electricity produced by the upper ORC powers the PEME for hydrogen production while freshwater production is supported by the combined output from the lower ORC LNG turbine and SOFC. A detailed thermo-economic analysis assesses the system’s efficiency and economic feasibility. Optimization efforts focus on three areas: electrical efficiency hydrogen and freshwater production using artificial neural networks (ANN) and genetic algorithms (GA). The optimization results reveal that Ammonia-propylene excels in electrical efficiency R1234ze(Z)-ethylene in net power output R1233zd(E)-propylene in cost-effectiveness R1234ze(Z)-propylene in hydrogen production and Ammonia-ethane in water production. The study offers valuable insights into enhancing the efficiency cost-effectiveness and sustainability of integrated energy systems.

Developing clean and renewable energy instead of the ones related to hydrocarbon resources has been known as one of the different ways to guarantee reduced greenhouse gas emissions. Geothermal systems and native hydrogen exploration could represent an opportunity to diversify the global energy matrix and lower carbon-related emissions. All of these natural energy sources require a well to be drilled for its access and/or extractions similar to the petroleum industry. The main focuses of this technical–scientific contribution and research are (i) to evaluate the global energy matrix; (ii) to show the context over the years and future perspectives on geothermal systems and natural hydrogen exploration; and (iii) to present and analyze the importance of developing technologies on drilling process optimization aiming at accessing these natural energy resources. In 2022 the global energy matrix was composed mainly of nonrenewable sources such as oil natural gas and coal where the combustion of fossil fuels produced approximately 37.15 billion tons of CO2 in the same year. In 2023 USD 1740 billion was invested globally in renewable energy to reduce CO2 emissions and combat greenhouse gas emissions. In this context currently about 353 geothermal power units are in operation worldwide with a capacity of 16335 MW. In addition globally there are 35 geothermal power units under pre-construction (project phase) 93 already being constructed and recently 45 announced. Concerning hydrogen the industry announced 680 large-scale project proposals valued at USD 240 billion in direct investment by 2030. In Brazil the energy company Petroleo Brasileiro SA (Petrobras Rio de Janeiro Brazil) will invest in the coming years nearly USD 4 million in research involving natural hydrogen generation and since the exploration and access to natural energy resources (oil and gas natural hydrogen and geothermal systems among others) are achieved through the drilling of wells this document presents a technical–scientific contextualization of social interest.

The widespread penetration of hydrogen in mainstream energy systems requires hydrogen production processes to be economically competent and environmentally efficient. Hydrogen if produced efficiently can play a pivotal role in decarbonizing the global energy systems. Therefore this study develops a framework which evaluates hydrogen production processes and quantifies deficiencies for improvement. The framework integrates slack-based data envelopment analysis (DEA) with fuzzy analytical hierarchy process (FAHP) and fuzzy technique for order of preference by similarity to ideal solution (FTOPSIS). The proposed framework is applied to prioritize the most efficient and sustainable hydrogen production in Pakistan. Eleven hydrogen production alternatives were analyzed under five criteria including capital cost feedstock cost O&M cost hydrogen production and CO2 emission. FAHP obtained the initial weights of criteria while FTOPSIS determined the ultimate weights of criteria for each alternative. Finally slack-based DEA computed the efficiency of alternatives. Among the 11 three alternatives (wind electrolysis PV electrolysis and biomass gasification) were found to be fully efficient and therefore can be considered as sustainable options for hydrogen production in Pakistan. The rest of the eight alternatives achieved poor efficiency scores and thus are not recommended.

In this paper we propose an alternative strategy to produce green hydrogen in a more sustainable way than standard water electrolysis where a substantial amount of the electrical energy is wasted in the oxygen evolution quite often simply released in the atmosphere. The HER (hydrogen evolution reaction) is effectively coupled with the oxidation of guaiacol at the anode leading to the simultaneous production of H2 and valuable guaiacol oligomers. Significative points i) a substantial decrease of the potential difference for the HER 0.85 V with guaiacol ii) HER is accompanied by the production of industrially appealing and sustainable guaiacol based oligomers iii) guaiacol oxidation runs efficiently on carbon-based surfaces like graphite and glassy carbon which are cheap and not-strategic materials. Then the electrochemical oxidation mechanism of guaiacol is studied in detail with in-situ EPR measurements and post-electrolysis product characterization: LC-DAD LC-MS and NMR. Experimental results and theoretical calculations suggest that guaiacol polymerization follows a Kane-Maguire mechanism.

In Spain the winery industry exerts a great influence on the national economy. Proportional to the scale of production a significant volume of waste is generated estimated at 2 million tons per year. In this work a laboratory-scale reactor was used to study the feasibility of the energetic valorization of winery effluents into hydrogen by means of dark fermentation and its subsequent conversion into electrical energy using fuel cells. First winery wastewater was characterized identifying and determining the concentration of the main organic substrates contained within it. To achieve this a synthetic winery effluent was prepared according to the composition of the winery wastewater studied. This effluent was fermented anaerobically at 26 ◦C and pH = 5.0 to produce hydrogen. The acidogenic fermentation generated a gas effluent composed of CO2 and H2 with the percentage of hydrogen being about 55% and the hydrogen yield being about 1.5 L of hydrogen at standard conditions per liter of wastewater fermented. A gas effluent with the same composition was fed into a fuel cell and the electrical current generated was monitored obtaining a power generation of 1 W·h L−1 of winery wastewater. These results indicate that it is feasible to transform winery wastewater into electricity by means of acidogenic fermentation and the subsequent oxidation of the bio-hydrogen generated in a fuel cell.

A comprehensive literature review highlights how the nature of active metals support materials promoters and synthesis methods influences catalytic performance with particular attention to ruthenium-based catalysts as the current benchmark. Kinetic models are presented to describe the reaction pathway and predict catalyst behavior. Various reactor configurations including fixed-bed membrane catalytic membrane perovskitebased and microreactors are evaluated in terms of their suitability for ammonia decomposition. While ruthenium remains the benchmark catalyst alternative transition metals such as iron nickel and cobalt have also been investigated although they typically require higher operating temperatures (≥500 °C) to achieve comparable conversion levels. At the industrial scale catalyst development must balance performance with cost. Inexpensive and scalable materials (e.g. MgO Al2O3 CaO K Na) and simple preparation techniques (e.g. wet impregnation incipient wetness) may offer lower performance than more advanced systems but are often favored for practical implementation. From a reactor engineering standpoint membrane reactors emerge as the most promising technology for combining catalytic reaction and product separation in a single unit operation. This review provides a critical overview of current advances in ammonia decomposition for hydrogen production offering insights into both catalytic materials and reactor design strategies for sustainable energy applications.

The production of hydrogen through water electrolysis has emerged as a promising alternative to decarbonizing the energy sector especially when integrated with renewable energy sources. Among the key operational parameters that affect electrolysis performance temperature and current density play a critical role in determining the energy efficiency hydrogen yield and durability of the system. The study presents a Systematic Literature Review (SLR) that includes peer-reviewed publications from 2018 to 2025 focusing on the effects of temperature and current density across a variety of electrolysis technologies including alkaline (AEL) proton exchange membrane (PEMEL) and solid oxide electrolysis cells (SOEC). A total of seven high-quality studies were selected following the PRISMA 2020 framework. The results show that high temperatures improve electrochemical kinetics and reduce excess potential especially in PEM and SOEC systems but can also accelerate component degradation. Higher current densities increase hydrogen production rates but lead to lower Faradaic efficiency and increased material stress. The optimal operating range was identified for each type of electrolysis with PEMEL performing best at 60–80 ◦C and 500–1000 mA/cm2 and SOEC at >750 ◦C. In addition system-level studies emphasize the importance of integrating hydrogen production with flexible generation and storage infrastructure. The review highlights several research gaps including the need for dynamic modeling multi-parameter control strategies and techno-economic assessments. These findings provide a basic understanding for optimizing hydrogen electrolysis systems in low-carbon energy architectures.

Hydrogen (H2) yields from various gasification and hydrothermal processes demonstrate significant variability depending on feedstock catalysts and process parameters. This systematic review explores hydrogen production through hydrochar-based gasification technologies focusing on the unique properties of hydrochar derived from biomass. Known for its ability to enhance syngas production especially hydrogen hydrochar’s porous structure high surface area and active catalytic sites significantly improve syngas quality and hydrogen yield. Studies show that supercritical water gasification (SCWG) of almond shells with hydrochars yielded up to 11.63 mmol/g while catalytic subcritical and SCWG of waste tires reached 19.7 mmol/g. Hydrothermal carbonization (HTC) coupled with gasification yields as high as 76.7 g H2/kg biochar for sewage sludge hydrochar with processes like anaerobic digestion and HTC producing 1278 mL/g from hemp hurd hydrochar. Key aspects such as the catalytic influence of hydrochar the role of additives and co-catalysts and optimization of gasification parameters including temperature pressure and equivalence ratios are explored. The review also delves into hydrochar preparation advancements such as alkali and alkaline earth metals (AAEMs) incorporation and highlights hydrochar’s role in reducing tar formation enhancing H2/CO ratios and stabilizing syngas heating value.

The industrial sector’s movement toward decarbonization is regarded as essential for governments. This paper assesses a system that uses only solar energy to synthesize liquid hydrogen and ammonia as energy carriers. Photovoltaic modules deliver electrical power while parabolic dish collectors are responsible for directing thermal energy to the solid oxide electrolyzer for hydrogen production which then mixes with nitrogen to produce ammonia after a number of compression stages. To investigate the proposed system comprehensive thermodynamic and exergo-economic studies are performed using an engineering equation solver and ASPEN PLUS software.

The present work aims to develop a uniquely designed experimental test rig for hydrogen (H2) production from hydrogen sulfide (H2S) and perform performance tests. The experimental activity focuses on the FeCl3 hybrid process for H2S cracking followed by H2S absorption sulfur purification and electrolysis for efficient H2 production. Hydrogen production is studied using KOH and FeCl3 electrolytes under varying temperatures between 20-80 ◦C. An electrochemical impedance spectroscopy (EIS) is employed to characterize the electrochemical cell under potentiostatic (0.5-2.0 V) and galvanostatic (0-0.5 mA) modes to analyze the system’s electrochemical response. The study results showed that hydrogen production increased by over 426 % from 20 ◦C to 80 ◦C. EIS analysis under potentiostatic mode showed Nyquist semicircle diameter reduced as the applied voltage increased from 0.5 V to 1.5 V and phase angle shifted from -5.59◦ to -1.27◦ confirming enhanced conductivity. Under galvanostatic mode the impedance dropped from ~25 Ω to ~21 Ω as current increased demonstrating improved kinetics for efficient H2 production.

Green hydrogen plays a vital role in facilitating the transition to sustainable energy systems with stable and high-capacity offshore wind resources serving as an ideal candidate for large-scale green hydrogen production. However as the capacity of offshore wind turbines continues to grow the increasing size and weight of these systems pose significant challenges for installation and deployment. This study investigates the application of high-temperature superconducting (HTS) materials in the generator and the power conducting cables as a promising solution to these challenges. Compared to conventional wind turbines HTS wind turbines result in significant reductions in weight and size while simultaneously enhancing power generation and transmission efficiency. This paper conducts a comprehensive review of mainstream electrolysis-based hydrogen production technologies and advanced hydrogen storage methods. The main contribution of this research is the development of an innovative conceptual framework for a superconducting offshore windto-hydrogen energy system where a small amount of liquid hydrogen is used to provide a deep-cooling environment for the HTS wind turbine and the remaining liquid hydrogen is used for the synthesis of ammonia as a final product. Through functional analysis this study demonstrates its potential for enabling large-scale offshore hydrogen production and storage. Additionally this paper discusses key challenges associated with real-world implementation including optimizing the stability of superconducting equipment and ensuring component coordination. The findings offer crucial insights for advancing the offshore green hydrogen sector showing that HTS technology can significantly enhance the energy efficiency of offshore wind-to-hydrogen systems. This research provides strong technical support for achieving carbon neutrality and fostering sustainable development in the offshore renewable energy sector.

High-temperature electrolysis offers a solution for industry decarbonisation by high-efficiency hydrogen production. This study presents a system based on Solid Oxide Electrolysis Cells (SOEC) fed by photovoltaic and waste heat recovery for hydrogen blending with natural gas in industrial burners. The aim of this work is to assess techno-economic feasibility of the proposed configuration investigating hydrogen blending limits Levelized Cost of Hydrogen (LCOH) and decarbonisation cost. LCOH values below 6 €/kgH2 cannot be achieved at current SOEC costs. The system can be applied without significant burner modifications since maximum hydrogen volumetric fractions are less than 20 %. Higher efficiency and emission reduction potential in comparison to alkaline electrolysers can be achieved but they are offset by higher LCOH and carbon abatement costs. Forthcoming reduction in SOEC costs can improve the cost-effectiveness and high natural gas prices experienced during the energy crisis make the decarbonisation cost competitive with the emission trading system.

N-type sulfide semiconductors are promising photocatalysts due to their broad visible-light absorption facile synthesis and chemical diversity. However photocorrosion and limited electron transport in one-step excitation and solid-state Z-scheme systems hinder efficient overall water splitting. Liquidphase Z-schemes offer a viable alternative but sluggish mediator kinetics and interfacial side reactions impede their construction. Here we report a stable Z-scheme system integrating n-type CdS and BiVO₄ with a [Fe(CN)₆]³⁻/[Fe(CN)₆]⁴⁻ mediator achieving 10.2% apparent quantum yield at 450 nm with stoichiometric H₂/O₂ evolution. High activity reflects synergies between Pt@CrOx and Co3O4 cocatalysts on CdS and cobalt-directed facet asymmetry in BiVO₄ resulting in matched kinetics for hydrogen and oxygen evolution in a reversible mediator solution. Stability is dramatically improved through coating CdS and BiVO4 with different oxides to inhibit Fe4[Fe(CN)6]3 precipitation and deactivation by a hitherto unrecognized mechanism. Separate hydrogen and oxygen production is also demonstrated in a twocompartment reactor under visible light and ambient conditions. This work unlocks the long-sought potential of n-type sulfides for efficient durable and safe solar-driven hydrogen production.

Hydrogen plays a key role in many industrial applications and is currently seen as one of the most promising energy vectors. Many efforts are being made to produce hydrogen with zero CO 2 footprint via water electrolysis powered by renewable energies. Nevertheless the use of fossil fuels is essentialin the short term. The conventional coal gasification and steam methane reforming processes for hydrogen production are undesirable due to the huge CO2 emissions. A cleaner technologybased on natural gas that has received special attention in recent years is methane pyrolysis. The thermal decomposition of methane gives rise to hydrogen and solid carbon and thus the release of greenhouse gases is prevented. Therefore methane pyrolysis is a CO2-free technology that can serve as a bridge from fossil fuels torenewable energies.

As global energy demand increases and reliance on fossil fuels becomes unsustainable hydrogen presents a promising clean energy alternative due to its high energy density and potential for significant CO2 emission reductions. However current hydrogen production methods largely depend on fossil fuels contributing to considerable CO2 emissions and underscoring the need to transition to renewable energy sources and improved production technologies. Life Cycle Analysis (LCA) is essential for evaluating and optimizing hydrogen production by assessing environmental impacts such as Global Warming Potential (GWP) energy consumption toxicity and water usage. The key findings indicate that energy sources and feedstocks heavily influence the environmental impacts of hydrogen production. Hydrogen production from renewable energy sources particularly wind solar and hydropower demonstrates significantly lower environmental impacts than grid electricity and fossil fuel-based methods. Conversely hydrogen production from grid electricity primarily derived from fossil fuels shows a high GWP. Furthermore challenges related to data accuracy economic analysis integration and measuring mixed gases are discussed. Future research should focus on improving data accuracy assessing the impact of technological advancements and exploring new hydrogen production methods. Harmonizing assessment methodologies across different production pathways and standardizing functional units such as “1 kg of hydrogen produced “ are critical for enabling transparent and consistent sustainability evaluations. Techniques such as stochastic modelling and Monte Carlo simulations can improve uncertainty management and enhance the reliability of LCA results.

Hydrogen gas is a promising clean-energy vector that can alleviate the current imbalance between energy supply and demand diversify the energy portfolio and underpin the sustainable development of oil and gas resources. This study pinpoints the factors that govern hydrogen quantification by pulsed-neutron logging. Monte Carlo simulations were performed to map the spatial distribution of capture γ-rays in formations saturated with either water or hydrogen and to systematically assess the effects of pore-fluid composition hydrogen density gas saturation lithology and borehole-fluid type. The results show that the counts of capture γ-rays are litter in hydrogen-bearing formations. For lowto moderate-porosity rocks the dynamic response window for hydrogensaturated pores is approximately 10% wider than that for methane-saturated pores. Increasing hydrogen density or decreasing gas saturation raises the capture-γ ratio while narrowing the dynamic range. Changes in borehole fluid substantially affect the capture-γ ratio yet have only a minor impact on the dynamic range. Lithology imposes an additional control: serpentinite enriched in structural water generates markedly higher capture-γ ratios that may complicate the quantitative evaluation of hydrogen.

Hydrogen has the potential to revolutionize how we power our lives from transportation to energy production. This study aims to compare the climate change impacts and the main factors affecting them for different categories of hydrogen production including grey hydrogen (SMR) blue hydrogen (SMR-CCS) turquoise hydrogen (TDM) and green hydrogen (PEM electrolysis). Grey hydrogen blue hydrogen and turquoise hydrogen which are derived from fossil sources are produced using natural gas and green hydrogen is produced from water and renewable electricity sources. When considering natural gas as a feedstock it is sourced from the pipeline route connected to Russia and through the liquefied natural gas (LNG) route from the USA. The life cycle assessment (LCA) result showed that grey hydrogen had the highest emissions with the LNG route showing higher emissions 13.9 kg CO2 eq. per kg H2 compared to the pipeline route 12.3 kg CO2 eq. per kg H2. Blue hydrogen had lower emissions due to the implementation of carbon capture technology (7.6 kg CO2 eq. per kg H2 for the pipeline route and 9.3 kg CO2 eq. per kg H2 for the LNG route) while turquoise hydrogen had the lowest emissions (6.1 kg CO2 eq. per kg H2 for the pipeline route and 8.3 kg CO2 eq. per kg H2 for the LNG route). The climate change impact showed a 12–25% increase for GWP20 compared to GWP100 for grey blue and turquoise hydrogen. The production of green hydrogen using wind energy resulted in the lowest emissions (0.6 kg CO2 eq. per kg H2) while solar energy resulted in higher emissions (2.5 kg CO2 eq. per kg H2). This article emphasizes the need to consider upstream emissions associated with natural gas and LNG extraction compression liquefaction transmission and regasification in assessing the sustainability of blue and turquoise hydrogen compared to green hydrogen.

A key factor in reducing the cost of green hydrogen production projects using water electrolysis systems is to minimize the degradation of the electrolyzer stacks as this impacts the lifetime of the stacks and therefore the frequency of their replacement. To create a better understanding of the economics of stack degradation we present a linear optimization approach minimizing the costs of a green hydrogen supply chain including an electrolyzer with degradation modeling. By calculating the levelized cost of hydrogen depending on a variable degradation threshold the cost optimal time for stack replacement can be identified. We further study how this optimal time of replacement is affected by sensitivities such as the degradation scale the load-dependency of both degradation and energy demand and the costs of the electrolyzer. The variation of the identified major sensitivity degradation scale results in a difference of up to 9 years regarding the cost optimal time for stack replacement respectively lifetime of the stacks. Therefore a better understanding of the degradation impact is imperative for project cost reductions which in turn would support a proceeding hydrogen market ramp-up.

This prospective life cycle assessment (LCA) compares the environmental impacts of alkaline electrolyser (AE) and proton exchange membrane (PEM) electrolyser systems for green hydrogen production with a special focus on the stack components. The study evaluates both baseline and near-future advanced designs considering cradle-to-gate life cycle from material production to operation. The electricity source followed by the stacks are identified as major contributors to environmental impacts. No clear winner emerges between AE and PEM in relation to environmental impacts. The advanced designs show a reduced impact in most categories compared to baseline designs which can mainly be attributed to the increased current density. Advanced green hydrogen production technologies outperform grey and blue hydrogen production technologies in all impact categories except for minerals and metals resource use due to rare earth metals in the stacks. Next to increasing current density decreasing minimal load requirements. improving sustainable mining practices (including waste treatment) and low carbon intensity steel production routes can enhance the environmental performance of electrolyser systems aiding the transition to sustainable hydrogen production.

The transition toward low-carbon energy systems requires reliable tools for assessing renewable-based hydrogen production under real-world climatic and economic conditions. This study presents a novel probabilistic framework integrating the following three complementary elements: (1) a Photovoltaic Geographical Information System (PVGIS) for high-resolution location-specific solar energy data; (2) Metalog probability distributions for advanced modeling of variability and uncertainty in photovoltaic (PV) energy generation; and (3) Levelized Cost of Hydrogen (LCOH) calculations to evaluate the economic viability of hydrogen production systems. The methodology is applied to three diverse European locations—Lublin (Poland) Budapest (Hungary) and Malaga (Spain)—to demonstrate regional differences in hydrogen production potential. The results indicate annual PV energy yields of 108.3 MWh 124.6 MWh and 170.95 MWh respectively which translate into LCOH values of EUR 9.67/kg (Poland) EUR 8.40/kg (Hungary) and EUR 6.13/kg (Spain). The probabilistic analysis reveals seasonal production risks and quantifies the probability of achieving specific monthly energy thresholds providing critical insights for designing systems with continuous hydrogen output. This combined use of a PVGIS Metalog and LCOH calculations offers a unique decision-support tool for investors policymakers and SMEs planning green hydrogen projects. The proposed methodology is scalable and adaptable to other renewable energy systems enabling informed investment decisions and improved regional energy transition strategies.

Methanol steam reforming (MSR) represents a highly promising pathway for sustainable hydrogen production due to its favorable hydrogen-to-carbon ratio and relatively low operating temperatures. The performance of the MSR process is strongly dependent on the selection and rational design of catalysts which govern methanol conversion hydrogen selectivity and the suppression of undesired side reactions such as carbon monoxide formation. Moreover advancements in reactor configuration and thermal management strategies play a vital role in minimizing heat loss and enhancing heat and mass transfer efficiency. Effective carbon monoxide removal technologies are indispensable for obtaining high-purity hydrogen particularly for applications sensitive to CO contamination. This review systematically summarizes recent progress in catalyst development reactor design and gas purification technologies for MSR. In addition the key technical challenges and potential future directions of the MSR process are critically discussed. The insights provided herein are expected to contribute to the development of more efficient stable and scalable MSR-based hydrogen production systems.

Given the rising interest in hydrogen economy alternative feedstocks are explored for their potential use for hydrogen production such as H2S a notable byproduct from oil and gas operations. This study presents a computational investigation on the thermodynamics kinetics and mechanisms of non-catalytic H2S-steam reforming (H2SSR) as a pathway for H2S-to-H2 benchmarked to H2S thermal decomposition (H2SPyrol) (as a limiting case without water). The mechanism integrates key elementary steps form different reaction pathways including H2S partial oxidation H2O reduction and H2S thermal decomposition. Results from the model are validated using available experimental data for H2SPyrol and H2SSR. Homogeneous gas-phase reactions are modelled at different H2O:H2S ratios reaction temperatures pressure and times. Thermodynamically the H2SSR reaction is unfavorable due to the presence of water and its role in increasing the reaction complexity and endothermicity; however kinetically water contributes to increasing the hydrogen yield at least 9 times that from H2SPyrol achieving 99.23 % H2S conversion at 1473 K with an excess H2O:H2S feed ratio of 200:1. The contribution of water during the H2SSR reaction is interpreted using reaction path and rate of production analyses demonstrating its role in producing an abundant pool of OH and H radicals. These radicals catalyze the cleavage of H2S-SH bonds accelerating hydrogen production at an optimal reaction time of 0.07–0.105 s. This study paves the path for future kinetic and catalytic research to optimize the technical viability of H2SSR as a promising H2S-to-H2 conversion pathway for sour wastewater reutilization.

The carbon-neutral and carbon-negative energy utilization technologies have long been people pursued to realize the strategic objective of carbon neutrality. Herein we propose a cation-exchange membrane (CEM) direct formate-CO2 fuel cell that possesses the capability of simultaneously generating electricity and producing hydrogen as well as continuously transforming carbon dioxide into pure sodium bicarbonate. Using the CO2- derived formate fuel the roof-of-concept CEM direct formate-CO2 fuel cell exhibits a peak power density of 38 mW cm− 2 at 80 ◦C without the assistance of additional electrolyte. The fairly stable constant-current discharge curve along with the detected hydrogen and pure sodium bicarbonate prove the conceptual feasibility of this electricity‑hydrogen-bicarbonate co-production device. By adding alkaline electrolyte to the anode we achieved a higher peak power density of 63 mW cm− 2 at the corresponding hydrogen production rate of 0.57 mL min− 1 cm− 2 . More interestingly the concentrations of pure NaHCO3 solution can be controlled by adjusting the cathode water flow rate and fuel cell discharge current density. This work presents a theoretically feasible avenue for coupling hydrogen production and CO2 utilization.

Scaling up water electrolyzers for green hydrogen production poses challenges in predicting megawatt-to gigawatt (MW/GW)-class system behavior under renewable energy power fluctuations. A fundamental evaluation is warranted to connect the characteristics of W- to kW-class laboratory electrolyzers with those of MW- to GW-class systems in practical applications. This study evaluates a 50 kW-class proton exchange membrane water electrolyzer with 30 cells using an accelerated degradation test protocol a simulated renewable energy power and a constant current of 800 A (1.33 A cm− 2 ) and the results show average degradation rates per cell of 40.4 27.2 and 5.6 μV h− 1 respectively. Evidently a voltage as approximate indicator exists for each cell to effectively suppress degradation. Durability tests reveal reductions in anode catalyst loading on the membrane electrode assemblies and inhomogeneous oxidation of the anode current collector. The findings contribute to predicting the stacking performance of electrolyzers for practical applications.

Methane pyrolysis produces hydrogen (H2) with solid carbon black as a co-product eliminating direct CO2 emissions and enabling a low-carbon supply when combined with renewable or low-carbon heat sources. In this study we propose a hybrid geothermal pyrolysis configuration in which an enhanced geothermal system (EGS) provides baseload preheating and isothermal holding while either electrical or solar–thermal input supplies the final temperature rise to the catalytic set-point. The work addresses four main objectives: (i) integrating field-scale geothermal operating envelopes to define heatintegration targets and duty splits; (ii) assessing scalability through high-pressure reactor design thermal management and carbon separation strategies that preserve co-product value; (iii) developing a techno-economic analysis (TEA) framework that lists CAPEX and OPEX incorporates carbon pricing and credits and evaluates dual-product economics for hydrogen and carbon black; and (iv) reorganizing state-of-the-art advances chronologically linking molten media demonstrations catalyst development and integration studies. The process synthesis shows that allocating geothermal heat to the largest heat-capacity streams (feed recycle and melt/salt hold) reduces electric top-up demand and stabilizes reactor operation thereby mitigating coking sintering and broad particle size distributions. Highpressure operation improves the hydrogen yield and equipment compactness but it also requires corrosion-resistant materials and careful thermal-stress management. The TEA indicates that the levelized cost of hydrogen is primarily influenced by two factors: (a) electric duty and the carbon intensity of power and (b) the achievable price and specifications of the carbon co-product. Secondary drivers include the methane price geothermal capacity factor and overall conversion and selectivity. Overall geothermal-assisted methane pyrolysis emerges as a practical pathway to turquoise hydrogen if the carbon quality is maintained and heat integration is optimized. The study offers design principles and reporting guidelines intended to accelerate pilot-scale deployment.

Photocatalytic membrane reactors (PMRs) which combine photocatalysis with membrane separation represent a pivotal technology for sustainable water treatment and resource recovery. Although extensive research has documented various configurations of photocatalytic-membrane hybrid processes and their potential in water treatment applications a comprehensive analysis of the interrelationships among reactor architectures intrinsic physicochemical mechanisms and overall process efficiency remains inadequately explored. This knowledge gap hinders the rational design of highly efficient and stable reactor systems—a shortcoming that this review seeks to remedy. Here we critically examine the connections between reactor configurations design principles and cutting-edge applications to outline future research directions. We analyze the evolution of reactor architectures relevantreaction kinetics and key operational parameters that inform rational design linking these fundamentals to recent advances in solar-driven hydrogen production CO2 conversion and industrial scaling. Our analysis reveals a significant disconnect between the mechanistic understanding of reactor operation and the system-level performance required for innovative applications. This gap between theory and practice is particularly evident in efforts to translate laboratory success into robust and economically feasible industrial-scale operations. We believe that PMRs willrealize theirtransformative potential in sustainable energy and environmental applications in future.

The main component of the hydrogen production system is the electrolyzer (EL) which is used to convert electrical energy and water into hydrogen and oxygen. The power converter supplies the EL and the controller is used to ensure the global stability and safety of the overall system. This review aims to investigate and analyze each one of these components: Proton Exchange Membrane Electrolyzer (PEM EL) electrical modeling DC/DC power converters and control approaches. To achieve this desired result a review of the literature survey and an investigation of the PEM EL electrical modeling of the empirical and semi-empirical including the static and dynamic models are carried out. In addition other sub-models used to predict the temperature gas flow rates (H2 and O2 ) hydrogen pressure and energy efficiency for PEM EL are covered. DC/DC power converters suitable for PEM EL are discussed in terms of efficiency current ripple voltage ratio and their ability to operate in the case of power switch failure. This review involves analysis and investigation of PEM EL control strategies and approaches previously used to achieve control objectives robustness and reliability in studying the DC/DC converter-PEM electrolyzer system. The paper also highlights the online parameter identification of the PEM electrolyzer model and adaptive control issues. Finally a discussion of the results is developed to emphasize the strengths weaknesses and imperfections of the literature on this subject as well as proposing ideas and challenges for future work.

In the search of low-carbon hydrogen production routes this study evaluates four biomass gasification processes: conventional steam gasification (CSG) sorption-enhanced gasification (SEG) and their solar-assisted variants (SSG and SSEG). The comparison focuses on three key aspects: hydrogen production overall energy efficiency (to H2 and power) and carbon capture potential (generation of a pure CO2 process stream for storage or utilization). For a realistic comparison a pseudo-equilibrium model of a double-bed gasifier was developed based on experimental correlations of char conversion under conventional and SEG conditions. The solar processes were designed for stable year-round operation considering seasonal weather variations by appropriately dimensioning the heliostat field and the thermal and chemical energy storage systems whose inventory dynamics were modelled. Both the gasifier and central solar tower models were rigorously validated with published data enhancing the reliability of the results. Solar-assisted configurations significantly outperform non-solar ones in hydrogen production with SSEG yielding 128 kg H2/ton biomassdaf compared to 90–95 kg for non-solar options. SEG demonstrates superior carbon capture potential (76 %) while solar-assisted systems achieve higher energy efficiency (67–73 % vs. 60–63 % for non-solar). These results underscore the potential of solar-assisted gasification for sustainable hydrogen production offering enhanced yields improved efficiency and substantial carbon capture capabilities. Future work will involve economic and environmental analysis to determine the best overall configuration.

As highlighted by the recent roadmaps from the European Union and the United States water electrolysis is the most valuable high-intensity technology for producing green hydrogen. Currently two commercial low-temperature water electrolyzer technologies exist: alkaline water electrolyzer (A-WE) and proton-exchange membrane water electrolyzer (PEM-WE). However both have major drawbacks. A-WE shows low productivity and efficiency while PEM-WE uses a significant amount of critical raw materials. Lately the use of anion-exchange membrane water electrolyzers (AEM-WE) has been proposed to overcome the limitations of the current commercial systems. AEM-WE could become the cornerstone to achieve an intense safe and resilient green hydrogen production to fulfill the hydrogen targets to achieve the 2050 decarbonization goals. Here the status of AEM-WE development is discussed with a focus on the most critical aspects for research and highlighting the potential routes for overcoming the remaining issues. The Review closes with the future perspective on the AEM-WE research indicating the targets to be achieved.

Solid oxide electrolysis cells (SOECs) have emerged as a promising technology for efficient energy storage and CO2 utilization via H2O–CO2 co-electrolysis. While most previous studies focused on planar or tubular configurations this work investigated a novel flat tubular SOEC design using a comprehensive 3D multi-physics model developed in COMSOL Multiphysics 5.6. This model integrates charge transfer gas flow heat transfer chemical/electrochemical reactions and structural mechanics to analyze operational behavior and thermo-mechanical stress under different voltages and pressures. Simulation results indicate that increasing operating voltage leads to significant temperature and current density inhomogeneity. Furthermore elevated pressure improves electrochemical performance possibly due to increased reactant concentrations and reduced mass transfer limitations; however it also increases temperature gradients and the maximum first principal stress. These findings underscore that the design and optimization of flat tubular SOECs in H2O–CO2 co-electrolysis should take the trade-off between performance and durability into consideration.

Hydrogen production from natural gas or biogas at different purity levels has emerged as an important technology with continuous development and improvement in order to stand for sustainable and clean energy. Regarding biogas which can be obtained from multiple sources hydrogen production through the steam reforming of methane is one of the most important methods for its energy use. In that sense the role of catalysts to make the process more efficient is crucial normally contributing to a higher hydrogen yield under milder reaction conditions in the final product. The aim of this review is to cover the main points related to these catalysts as every aspect counts and has an influence on the use of these catalysts during this specific process (from the feedstocks used for biogas production or the biodigestion process to the purification of the hydrogen produced). Thus a thorough review of hydrogen production through biogas steam reforming was carried out with a special emphasis on the influence of different variables on its catalytic performance. Also the most common catalysts used in this process as well as the main deactivation mechanisms and their possible solutions are included supported by the most recent studies about these subjects.

In this work we present the simulation of a plant for the exploitation of renewable hydrogen (e.g. from biomass gasification) with production of renewable ammonia as hydrogen vector and energy storage medium. The simulation and sizing of all unit operations were performed with Aspen Plus® as software. Vegetable waste biomass is used as raw material for hydrogen production more specifically pine sawdust.<br/>The hydrogen production process is based on a gasification reactor operating at high temperature (700–800 °C) in the presence of a gasifying agent such as air or steam. At the outlet a solid residue (ash) and a certain amount of gas which mainly contains H2 CH4 CO and some impurities (e.g. sulphur or chlorine compounds) are obtained. Subsequently this gas stream is purified and treated in a series of reactors in order to maximize the hydrogen yield. In fact after the removal of the sulphur compounds through an absorption column with MEA (to avoid poisoning of the catalytic processes) 3 reactors are arranged in series: Methane Steam Reforming (MSR) High temperature Water-Gas Shift (HT-WGS) Low temperature Water-Gas Shift (LT-WGS).<br/>In the first MSR reactor methane reacts at 1000 °C in presence of steam and a nickel-based catalyst in order to obtain mainly H2 CO and CO2. Subsequently two steps of WGS are present to convert most of the CO into H2 and CO2. Also these reactions are carried out in the presence of a catalyst and with an excess of water.<br/>All the oxygenated compounds must be carefully eliminated: the remaining traces of CO are methanated while CO2 is removed by a basic scrubbing with MEA (35 wt%) inside an absorption column. The Haber-Bosch synthesis of ammonia was carried out at 200 bar and in a temperature range between 300 and 400 °C using two catalysts: Fe (wustite) and Ru/C.<br/>As overall balance from an hourly flow rate of 1000 kg of dry biomass and 600 kg of nitrogen 550 kg of NH3 at 98.8 wt% were obtained demonstrating the proof of concept of this newly designed process for the production of hydrogen from renewable waste biomass and its transformation into a liquid hydrogen vector to be easily transported and stored.

The current fossil fuel-based generation of energy has led to large-scale industrial development. However the reliance on fossil fuels leads to the significant depletion of natural resources of buried combustible geologic deposits and to negative effects on the global climate with emissions of greenhouse gases. Accordingly enormous efforts are directed to transition from fossil fuels to nonpolluting and renewable energy sources. One potential alternative is biohydrogen (H2) a clean energy carrier with high-energy yields; upon the combustion of H2 H2O is the only major by-product. In recent decades the attractive and renewable characteristics of H2 led us to develop a variety of biological routes for the production of H2. Based on the mode of H2 generation the biological routes for H2 production are categorized into four groups: photobiological fermentation anaerobic fermentation enzymatic and microbial electrolysis and a combination of these processes. Thus this review primarily focuses on the evaluation of the biological routes for the production of H2. In particular we assess the efficiency and feasibility of these bioprocesses with respect to the factors that affect operations and we delineate the limitations. Additionally alternative options such as bioaugmentation multiple process integration and microbial electrolysis to improve process efficiency are discussed to address industrial-level applications.

This study tested a cogeneration (desalination/hydrogen production) system with natural and black sand as sensible heat storage considering the thermal efficiencies environmental impact water quality cost aspects and hydrogen generation rate. The black sand-modified distiller attained the highest water production of 4645 mL more than the conventional distiller by 1595 mL. It also offered better energy and exergy efficiencies of 45.26% and 3.72% respectively compared to 32.10% and 2.19% for the conventional one. Both modified distillers showed impressive improvements in water quality by significant reductions in total dissolved solids (TDS) from 29300 mg/L to 60–61 mg/L. Moreover the black sand-modified still reduced chemical oxygen demand (COD) to 135 mg/L. The production cost was minimized by using black sand to 0.0111$/L higher than one-fifth in the case of the lab-based distiller. Regarding hydrogen production the highest rate was obtained using distilled water from a labbased distiller of 0.742 gH₂/hr with an energy efficiency of 11.00%; however it was not much higher than the case of black sand-modified still (0.736 gH₂/hr production rate and 10.91% efficiency). Moreover the black sand-modified still showed the highest annual exergy output of 70.4 kWh/year with a significant annual decarbonization of 1.69 ton-CO2.

Hydrogen is a critical enabler of CO2 valorization essential for the synthesis of carbon-neutral fuels such as efuels and advanced biofuels. Biohydrogen produced from renewable biomass is a stable and dispatchable source of low-carbon hydrogen helping to address supply fluctuations caused by the intermittency of renewable electricity and the limited availability of electrolytic hydrogen. This study experimentally demonstrates that sorption-enhanced steam reforming (SESR) is a robust and adaptable process for hydrogen production from biomass-derived syngas-like gas streams. By incorporating in situ CO2 capture SESR overcomes the thermodynamic limits of conventional reforming achieving high hydrogen yields (>96 %) and purities (up to 99.8 vol%) across a wide range of syngas compositions. The process maintains high conversion efficiency despite variations in CO CH4 and CO2 concentrations and sustains performance even with H2-rich feeds conditions that typically inhibit reforming reactions. Among the operating parameters temperature has the greatest influence on performance followed by the steam-to-carbon ratio and space velocity. Multi-objective optimization shows that SESR can maintain high hydrogen yield (>96 %) selectivity (>99 %) and purity (>99.5 vol%) within a moderately flexible operating window. Methane reforming is identified as the main performance-limiting step with a stronger constraint on H2 yield and purity than CO conversion through the water–gas shift reaction. In addition to hydrogen SESR produces a concentrated CO2 stream suitable for downstream utilization or storage. These results support the potential of SESR as a flexible and efficient approach for hydrogen production from heterogeneous renewable feedstocks.

Anion exchange membrane (AEM) alkaline water electrolyser s are a promising reactor in large - scale industrial green hydrogen production. However the configurations of electrolysers especially the flow channel are not well optimised. In this work we demonstrate that the several existing flow channel designs e.g. single serpentine parallel pin can significantly affect the AEM electrolysers’ performance. The two -phase flow behaviours associated with the mass transfer of both electrolyte and produced gas bubbles within these flow channels have been simulated and thoroughly studied via a three -dimensional (3D) computational fluid dynamics (CFD) model . A novel flow channel design named Parpentine that combines the features of Parallel and Single serpentine designs is proposed with an optimised balance among the electrolyte flow distribution bubble removal rate and pressure drop. The superiority of the Parpentine flow channel is well verified in practical AEM water electrolyser experiments using commercial Ni foam and self-designed efficient NiFe and NiMo electrodes. At a cell voltage of 2.5 V compared to the benchmark serpentine design a 12.4% ~ 34.8% increase in hydrogen production efficiency can be achieved in both 1 M and 5 M KOH conditions at room temperature. This work discovers a novel design and a new method for highly efficient water electrolysers.

Ammonia (NH3) has emerged as a promising hydrogen carrier due to its high hydrogen content favourable storage and transport properties and carbon-free utilisation. Its ability to be stored as a liquid under relatively mild conditions and its compatibility with existing industrial infrastructure make it an efficient and scalable solution for hydrogen distribution. This study conducts a detailed investigation into the kinetics of ammonia decomposition over rutheniumbased catalysts which are known for their high catalytic activity for ammonia cracking. Experimental data across a wide range of operating conditions are used to validate the proposed models with a promising catalyst (0.5 wt.% Ru/Al2O3). The study employs kinetic models based on different theoretical frameworks such as the Langmuir isotherm the Temkin-Pyzhev approach and the microkinetic model focusing on evaluating various rate-determining steps. A comparison of these models shows that those that consider nitrogen desorption a ratedetermining step provide the best predictions of NH3 conversion effectively capturing the dependencies on temperature and feed molar fractions of reactants and products. This multifaceted approach integrates experimental data with proposed kinetic models contributing to a better understanding of NH3 decomposition through parameter optimisation. The findings provide valuable insights for modelling catalytic reactors optimising conditions and enhancing catalyst performance for efficient hydrogen production from ammonia.

Green H2 production using electrolyzer technology is an emerging method in the current mandate using renewable-based power sources integrated with electrolyzer technology. Prior research has been extensively studied to understand the effects of intermittent power sources on the hydrogen production output. However in this context the characteristics of the working electrolyzer behave differently under system-level operation. In this paper we investigated a 25 kW alkaline electrolyzer for its stack performance in terms of stack efficiency the stack current vs. stack voltage and the relationship between the H2 flow rate and stack current. It was found that the current of 52 A produces the best system efficiency of 64% under full load operation for 1 h. The H2 flow rate behaves in an exponential asymptotic pattern and it is also found that the ramp-up time for hydrogen generation by the electrolyzer is significantly low thus marking it as an efficient option for producing green hydrogen with the input of a hybrid grid and renewable PV-based power sources. Hydrogen production techno-economic analysis has been conducted and the LCOH is found to be on the higher side for the current electrolyzer under investigation.

This study explored the optimization of green hydrogen production via seawater electrolysis powered by a hybrid photovoltaic (PV)-wind system in KwaZulu-Natal South Africa. A Box–Behnken Design (BBD) adapted from Response Surface Methodology (RSM) was utilized to address the synergistic effect of key operational factors on the integration of renewable energy for green hydrogen production and its economic viability. Addressing critical gaps in renewable energy integration the research evaluated the feasibility of direct seawater electrolysis and hybrid renewable systems alongside their techno-economic viability to support South Africa’s transition from a coal-dependent energy system. Key variables including electrolyzer efficiency wind and PV capacity and financial parameters were analyzed to optimize performance metrics such as the Levelized Cost of Hydrogen (LCOH) Net Present Cost (NPC) and annual hydrogen production. At 95% confidence level with regression coefficient (R2 > 0.99) and statistical significance (p < 0.05) optimal conditions of electricity efficiency of 95% a wind-turbine capacity of 4960 kW a capital investment of $40001 operational costs of $40000 per year a project lifetime of 29 years a nominal discount rate of 8.9% and a generic PV capacity of 29 kW resulted in a predictive LCOH of 0.124$/kg H2 with a yearly production of 355071 kg. Within the scope of this study with the goal of minimizing the cost of production the lowest LCOH observed can be attributed to the architecture of the power ratios (Wind/PV cells) at high energy efficiency (95%) without the cost of desalination of the seawater energy storage and transportation. Electrolyzer efficiency emerged as the most influential factor while financial parameters significantly affected the cost-related responses. The findings underscore the technical and economic viability of hybrid renewable-powered seawater electrolysis as a sustainable pathway for South Africa’s transition away from coal-based energy systems.

Hydrogen crossover limits the load range of alkaline water electrolyzers hindering their integration with renewable energy. This study examines the impact of the electrode-diaphragm gap on crossover focusing on diffusive transport. Both finite-gap and zero-gap designs employing the state-of-the-art Zirfon UTP Perl 500 and UTP 220 diaphragms were investigated at room temperature and with a 12 wt% KOH electrolyte. Experimental results reveal a relatively high crossover for a zero-gap configuration which corresponds to supersaturation levels at the diaphragm-electrolyte interface of 8–80 with significant fluctuations over time and between experiments due to an imperfect zero-gap design. In contrast a finite-gap (500 μm) has a significantly smaller crossover corresponding to supersaturation levels of 2–4. Introducing a cathode gap strongly decreases crossover unlike an anode gap. Our results suggest that adding a small cathode-gap can significantly decrease gas impurity potentially increase the operating range of alkaline electrolyzers while maintaining good efficiency.

A proton exchange membrane electrolyzer can effectively utilize the electricity generated by intermittent solar power. Different methods of generating electricity may have different efficiencies and hydrogen production rates. Two coupled systems namely PV/T- and CPV/T-coupling PEMEC respectively are presented and compared in this study. A maximum power point tracking algorithm for the photovoltaic system is employed and simulations are conducted based on the solar irradiation intensity and ambient temperature of a specific location on a particular day. The simulation results indicate that the hydrogen production is relatively high between 11:00 and 16:00 with a peak between 12:00 and 13:00. The maximum hydrogen production rate is 99.11 g/s and 29.02 g/s for the CPV/T-PEM and PV/T-PEM systems. The maximum energy efficiency of hydrogen production in CPV/T-PEM and PV/T-PEM systems is 66.7% and 70.6%. Under conditions of high solar irradiation intensity and ambient temperature the system demonstrates higher total efficiency and greater hydrogen production. The CPV/T-PEM system achieves a maximum hydrogen production rate of 2240.41 kg/d with a standard coal saving rate of 15.5 tons/day and a CO2 reduction rate of 38.0 tons/day. Compared to the PV/T-PEM system the CPV/T-PEM system exhibits a higher hydrogen production rate. These findings provide valuable insights into the engineering application of photovoltaic/thermal-coupled hydrogen production technology and contribute to the advancement of this field.