Hydrogen

Although austenitic steels have been implemented in direct liquid hydrogen (LH₂) contact for decades, detailed microstructural and mechanical studies are still rare at a temperature of 20 K and inexistent for long-term exposure in LH₂. Therefore, austenitic stainless-steel parts, which were in direct contact with LH₂, from a container for LH₂ transport from the company Linde GmbH that has been in service for over 30 years, was chosen as a material model system for this investigation. In the present work, the possible influence of cryogenic gaseous and liquid H₂ (GH₂ and LH₂) on the micro- and macroscopic as well as mechanical properties of the container was investigated. Monitoring the properties after long-term GH₂ and LH₂-exposed material assesses the durability and the failure characteristics of these austenitic steels. A mean content of 2.5 ppm H was detected in the container walls after the long-term exposure. The microhardness of the long-term GH₂ and LH₂ are similar to an H₂ non-exposed sample. Based on the SEM investigations, no microstructural change could be detected in the material after long-term H₂ exposure and the residual tensile properties are still similar to those of ‘fresh’ non-exposed material. The hydrogen embrittlement (HE) occurred in the container material only after additional thermal H-charging, where the ductility reduced to about 50% at 200 K. Full article

This study explores a photovoltaic/thermal (PV/T)-based electrolysis system designed for dual production of hydrogen fuel and domestic hot water (DHW), providing a sustainable energy solution amid rising global emissions. A dynamic rule-based control mechanism with hysteresis thresholds on hydrogen-storage state of charge (SoC) is implemented to balance electrolyzer operation with intermittent solar availability, maintaining PV/T power outputs while preventing storage overfilling and minimizing start–stop cycling. The system is assessed across 27 geographically diverse cities spanning a wide range of solar irradiation and energy price structures. Annual hydrogen yields range from 20 kg/yr in high-latitude locations (Helsinki, Stockholm) to 33.5 kg/yr in high-irradiation regions (Riyadh, Abu Dhabi), while the levelized cost of hydrogen (LCOH) spans from 6.47 USD/kg (Riyadh) to 22.86 USD/kg (Helsinki). Economically, the system achieves its strongest performance in solar-rich, high-energy-cost environments: Rome records the highest net annual cash flow (858.9 USD/yr) and shortest payback period (2.47 years), followed by Davos, Madrid, Brasília, and Canberra. In contrast, locations with subsidized energy tariffs—such as Algiers, Kyiv, and Tehran—yield low or negative net cash flows, rendering the system economically unviable without policy support. Environmental analysis reveals annual CO₂ avoidance ranging from 0.33 ton/yr (Stockholm) to 2.97 ton/yr (Riyadh), with a global mean of 1.095 ton/yr and a combined total of approximately 29.6 tons/yr across all examined sites. A machine learning model is developed to generalize performance predictions across unseen locations, achieving leave-one-out (LOO) R² values of 0.953 (net cash flow), 0.935 (LCOH), and 0.947 (LCO-DHW), with mean absolute errors below ±1 USD/kg and ±0.03 USD/kWh. The findings confirm that, under fixed capital cost assumptions, local electricity price and solar irradiation are the dominant drivers of economic viability, while grid carbon intensity and solar resource jointly govern environmental performance, with markets offering irradiation above 1500 kWh/m²·yr and electricity prices exceeding 0.2 USD/kWh representing the most promising deployment targets. Full article

High-temperature gaseous deuterium charging was used to investigate hydrogen isotope permeation, retention, microstructural stability, and fracture response in 310S austenitic stainless steel. Gas-driven permeation, thermal desorption spectroscopy, two-dimensional diffusion simulation, XRD/EBSD characterization, tensile testing, and fractographic analysis were combined to correlate isotope transport with mechanical and fracture behavior. The deuterium permeability and diffusion coefficient followed an Arrhenius relationship, and the diffusion coefficient extrapolated at 673 K was 1.11 × 10⁻¹¹ m²/s. With increasing charging time, the deuterium distribution evolved from a surface-enriched unsaturated state to an overall near-saturated state with higher retention. Although deuterium charging had little influence on yield strength, ultimate tensile strength, and elongation under the present room-temperature tensile condition, local quasi-cleavage-like facets, secondary cracks, and serrated fracture edges became more evident after charging. These results indicate that the embrittlement response of 310S stainless steel was mainly characterized by localized hydrogen-assisted damage rather than dominant brittle fracture. Full article

High-pressure gaseous hydrogen storage is widely adopted in the hydrogen energy industry chain due to its simplicity, reliability, and economic viability. However, when these systems are subjected to rapid filling, a series of complex thermodynamic behaviors are induced. These have been identified as a bottleneck restricting the safety and service life of hydrogen storage and transportation equipment. In this paper, a detailed review is conducted on the recent domestic and international research progress regarding the thermodynamic issues encountered during the charging process of storage devices. Research achievements related to the thermodynamics of the process are systematically classified, summarized and discussed. These achievements are analyzed from four aspects: thermodynamic theoretical models, numerical simulation analysis, experimental testing, and thermal management strategies. The thermodynamic mechanism of the charging process is revealed, and the variation laws of thermodynamic responses during charging are sorted out. Key factors affecting the thermodynamic behaviors of charging are clarified, and the implementation effects of different thermal management strategies are elaborated. Finally, based on the future development trend and prominent potential challenges in high-pressure hydrogen storage, the future development directions of the thermodynamics of hydrogen fueling in storage and transportation devices are explored and prospected. Full article

The use of differential pressure energy for green hydrogen and ammonia comes with significant safety challenges. Two zero-emission technical schemes—one based on magnetic coupling transmission and another based on dual magnetic fluid seals—were proposed and designed. The energy performance of both schemes was first analyzed for a DN200 pipe using the DWSIM software (Version 8.6.6). Subsequently, the levelized cost of electricity and the dynamic payback period were evaluated and compared. The results show that the magnetic coupling transmission scheme exhibits relatively low energy efficiency (54.9–61.7%), whereas the scheme based on dual magnetic fluid seals is more complex yet achieves higher energy efficiency (65.8–67.1%). The levelized electricity cost of both schemes under a differential pressure of 0.5 MPa is estimated to be lower than the feed-in tariff of coal-fired power plants in China, and the dynamic payback period is estimated to be less than 5.5 years. Overall, both schemes provide benefits in energy savings and profitability. These schemes warrant further experimental investigation and pilot testing. Full article

Pressure ulcers are chronic wounds characterized by repeated ischemia–reperfusion injury, persistent inflammation, and redox imbalance, in which excessive production of reactive oxygen species (ROS) contributes to delayed healing. Thus, debridement is an essential therapeutic procedure for removing necrotic tissue and biofilm, thereby reconstructing the wound microenvironment. Recent experimental studies suggest that molecular hydrogen may improve wound healing through attenuation of oxidative stress and modulation of inflammatory responses, while debridement represents a dynamic intervention phase in which redox imbalance may transiently develop. Here, we propose the hypothesis that the use of hydrogen-enriched saline as an irrigation solution during hydrosurgical debridement may attenuate excessive redox imbalance and stabilize the wound microenvironment during this dynamic intervention phase. Such intra-procedural modulation may facilitate the transition from inflammation to the proliferative phase of wound healing, thereby promoting tissue repair. This approach is expected to attenuate the transient oxidative burst following debridement, as reflected by reductions in redox-related biomarkers in the wound environment, including ROS levels and oxidative damage markers such as 8-hydroxy-2′-deoxyguanosine and lipid peroxidation products, with relative decreases in these biomarkers compared with conventional debridement, potentially consistent with reductions observed in preclinical oxidative stress models. These findings are consistent with findings from previous experimental studies demonstrating attenuation of oxidative stress markers following hydrogen administration. This hypothesis introduces a novel therapeutic concept, redox modulation during the debridement process, offering a practical strategy for integrating hydrogen-based therapy into existing wound management without altering current surgical techniques. Full article

The reaction of aluminum with water is a promising method for producing hydrogen on demand for autonomous energy systems. However, its practical implementation faces the challenge of process control due to high exothermicity, leading to particle sintering and thermal instability, especially when using highly reactive nanopowders. The goal of this study is to implement an integrated approach to controlling this reaction, aimed at minimizing these risks. The approach is based on the principle of spatial and temporal distribution of reactants to ensure uniform heat release. Two process management methods were investigated: electrostatic application of aluminum powder to the reactor walls with its gradual release and pre-treatment of a nanopowder-ice mixture. Using a macrokinetic mathematical model, calculations of the conversion kinetics and heat release were performed and compared with experimental data. The results showed that both methods prevent slurry self-heating and achieve uniform hydrogen generation at a constant rate. In particular, the use of a pre-frozen mixture ensured stable hydrogen production over a long period of time without additional heating or stirring. The proposed approaches can be used in the design of safe and efficient hydrogen generators for autonomous power plants. Full article

The main goal of this study was to develop and validate a laboratory-scale prototype of a rechargeable metal hydride (MH)–air battery integrating gas diffusion electrodes (GDEs) and MH electrodes with stable performance over extended operation (>500 h) and repeated charge–discharge cycling (>100 cycles). This work addresses the critical transition from optimized electrode materials to a functioning system by investigating its operation under deep-discharge conditions, a key but still insufficiently explored regime in the context of stationary renewable energy storage. In this respect, this study explicitly targets the practical applicability of the developed system rather than focusing solely on material-level performance. The most efficient electrode materials, previously optimized, were successfully integrated into a single-cell configuration and systematically evaluated under various operating conditions. By determining the limiting current density for stable GDE operation, an appropriate operating window was defined, enabling maximum capacity utilization without compromising electrode integrity. At a current density of 10 mA, the maximum depth of discharge was achieved at a cell voltage of 575 mV, ensuring operation in a regime that limits GDE degradation while maintaining high energy efficiency. In addition, the electrode retains its mechanical stability after operation is interrupted, indicating good structural robustness. Furthermore, the performance of two identical cells connected in series was investigated to assess system scalability. The cells were operated under near-limit conditions and exhibited stable behavior. Overall, the present results confirm that the developed MH–air battery system extends beyond laboratory-scale validation and shows strong potential for implementation in stationary energy storage applications. Full article

Decarbonizing maritime transport requires hydrogen storage technologies that are efficient, safe, and compatible with fuel cell systems. This study evaluates three hydrogen storage technologies (compressed hydrogen (CH₂), liquid hydrogen (LH₂), and metal hydrides (MH)) based on five key criteria: safety, autonomy, environmental impact, cost, and implementation feasibility. Applying two multi-criteria decision-making (MCDM) methods, Analytic Hierarchy Process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), the alternatives are systematically ranked to identify the most suitable option. Both methods consistently highlight compressed hydrogen as the most viable storage solution, offering a good balance of safety, infrastructure maturity, and economic performance. Liquid hydrogen, despite its superior autonomy, is limited by high energy and infrastructure costs. Metal hydrides, although safer and more compact in terms of volumetric density, are limited by low gravimetric efficiency at the system level due to the additional weight of the storage material and associated components. Full article

In the context of global carbon neutrality goals, substituting hydrogen for carbon as a reductant represents a critical pathway for mitigating emissions in the iron and steel industry. Hydrogen-based molten reduction technology, characterized by its rapid reaction kinetics and high feedstock flexibility, has emerged as a pivotal direction for the industry’s low-carbon transition. This article systematically reviews research progress on the hydrogen-based reduction of molten iron oxides. The thermodynamic behavior of molten systems is discussed, confirming the feasibility of reducing molten FeO with hydrogen at elevated temperatures. Furthermore, discrepancies and nonlinear characteristics within current mainstream thermodynamic databases regarding the high-temperature molten region are identified. Kinetic studies demonstrate that reduction rates in the molten state significantly exceed those in the solid state. The rate-limiting step is shown to vary with reaction conditions, primarily shifting between interfacial chemical reaction and liquid-phase mass transfer control. Additionally, the influence mechanisms of key parameters—including temperature, reaction time, gas flow rate, gas composition, and slag composition—on the reduction process are comprehensively reviewed. By synthesizing existing methodologies and theoretical advancements, this review aims to provide a theoretical reference for optimizing hydrogen-based molten reduction processes for iron oxides. Full article

Large-scale and long-term hydrogen storage is one of the main obstacles to the wider use of hydrogen as a possible substitute for natural gas. A solution could be depleted natural gas fields, which have proven capacity and are already geologically prospected. However, part of this field remains occupied by residual natural gas, meaning that hydrogen is mixed with natural gas during storage and purification after extraction is therefore necessary. The aim of this study was to design and evaluate a hydrogen purification process for separating hydrogen from natural gas after extraction from a depleted natural gas field while maintaining the required hydrogen purity and recovery. Input data provided by Nafta a.s. were used for the mathematical simulation of hydrogen separation throughout a 150-day extraction period. A mathematical model of membrane separation and pressure swing adsorption (PSA) was developed. A single membrane stage was only able to operate effectively during the first 50 days of withdrawal while maintaining at least 80% hydrogen recovery. A two-stage membrane configuration achieved hydrogen purity above 98% with final recoveries above 80–85%, while the hybrid membrane–PSA system enabled hydrogen purity of 99.8% and total recovery of 82.5% on the last day of extraction. Full article

The production of green hydrogen via aqueous electrolysis of hydrogen sulfide (H₂S) holds significant potential to address challenges related to sustainable energy generation and environmental protection. The electrocatalytic splitting of water polluted with highly toxic H₂S is attractive for industrial applications because the process: (i) is less power-consuming than direct thermal H₂S decomposition; (ii) achieves high Faradaic efficiencies for hydrogen production; and (iii) yields elemental sulfur as an added-value by-product. This review covers a brief discussion on sulfide-containing water sources and electrochemical methods for hydrogen production from H₂S, specifically Direct, Indirect, and Electrochemical Membrane Reactor (EMR) systems. To become commercially and economically attractive, these approaches require improvements in electrolysis efficiency through the development of low-cost electrode materials that are resistant to sulfur poisoning and corrosion, while possessing high catalytic activity, enhanced stability, and durability. Early research focused on carbon-based materials combined with noble metal oxides, transition metal compounds, and related materials. Since their practical performance is limited, investigations have shifted toward nanostructured electrocatalysts with unique crystal structures and designs, which show significantly improved efficiency for H₂S electrolysis. This review highlights the potential of H₂S electrolysis for hydrogen production, giving special attention to recent advancements in electrode materials. Full article

An empirical model of the kinetics of Hydrogen-Induced Cracking (HIC) in API 5L steels was derived using the best-fit equation for experimental data obtained from cathodic charging tests. The model represents the growth of both individual and interconnecting cracks, using a double exponential equation known as the Gumbel distribution. Current density was the main independent input variable, as it is related to the hydrogen influx during the cathodic charging experiment. The results indicated that in the initial hours of cathodic charging most of the available HIC nucleation sites are activated, the growth of these individual cracks being the main contribution to the overall kinetics. Further crack growth is due to the interconnection of individual cracks, decreasing the growth rate until it becomes nearly zero. The proposed model is used in a simulation algorithm that accurately describes the complete HIC kinetics, for both short- and long-term hydrogen charging exposure, reproducing the effects of applied current density on the total cracked area and growth rates. Finally, the simulation algorithm adequately predicts the spatial distribution of HIC in a bidimensional plane that emulates the detection of HIC by C-scan ultrasonic inspection. Full article

Hydrogen-enriched fuel injection in staged gas-turbine combustors is commonly achieved through jet-in-crossflow (JICF) configurations, where flame stabilization is governed by a local balance between flow-induced strain/mixing and chemical reaction rates. This work investigates turbulent reacting JICF relevant to staged combustion conditions using high-fidelity simulations with adaptive mesh refinement (AMR) and differential-diffusion effects together with Lagrangian particle statistics. Chemistry model uncertainties are incorporated by using a projection method that maps uncertainty estimates from detailed mechanisms into the model used in this work. Results show that the macroscopic flame topology remains in a stable two-branch regime (lee-stabilized and lifted) and is primarily controlled by the jet momentum–flux ratio J. Visualization of the normalized scalar dissipation rate reveals that the flame front resides on the low-dissipation side of intense mixing layers, occupying an intermediate region between over-strained and under-mixed regions. While hydrogen content does not significantly change the global stabilization mode for the cases studied, uncertainty analysis reveals composition-dependent differences that are not apparent in the mean behavior alone. In particular, visualization in Eulerian (χ, T) state-space analysis and particle statistics conditioned on the stoichiometric surface demonstrate that higher-hydrogen cases observe a lower scalar dissipation rate and exhibit substantially reduced variability in OH production under kinetic-parameter perturbations, whereas lower-hydrogen blends experience higher dissipation and amplified chemical sensitivity. These findings highlight that, even in globally similar JICF regimes, the hydrogen content can modify the local response of the flame to kinetic-parameter uncertainty, motivating uncertainty-aware interpretation and design for hydrogen-fueled staging systems. Full article

Hydrogen (H₂) was produced from recycled aluminum microparticles (180–250, 300–425, and 425–500 μm) via alkaline hydrolysis using a 1.0 M NaOH solution to enhance oxide layer removal and aluminum dissolution. Maximum hydrogen flow rates of approximately 13, 15, and 19 mL·min⁻¹ were obtained, confirming that smaller particle sizes promote faster reaction rates due to increased specific surface area. The hydrogen evolution exhibited two-stage kinetic behavior: an initial stage characterized by rapid aluminum dissolution and increasing H₂ production, followed by a gradual decline associated with the formation of a passivating Al(OH)₃ layer. Despite the higher reaction rates observed for smaller particles, the maximum cumulative hydrogen production was obtained for the intermediate particle size (363 µm, 132 mL), compared to 106 mL and 102 mL for 215 µm and 463 µm, respectively, indicating a trade-off between surface area and passivation effects. Kinetic analysis based on the shrinking core model showed excellent agreement (R² = 99.94–99.97%), with rate constants of 0.137, 0.064, and 0.050 min⁻¹. The relationship k ∝ d⁻ⁿ (n ≈ 1.4) suggests a mixed kinetic regime involving both surface reaction and diffusion through the Al(OH)₃ layer. These findings indicate that hydrogen generation can be modulated by particle size; however, the relatively low flow rates and yields limit its immediate practical applicability. Full article

Hydrogen is a clean energy carrier with broad application potential. This study focuses on improving hydrogen production efficiency in a proton exchange membrane (PEM) electrolyzer system that integrates a photovoltaic (PV) array, a battery energy storage system, and the electrolyzer. The PV array is interfaced with the electrolyzer through a buck converter using a maximum power point tracking (MPPT) algorithm to ensure maximum energy harvesting. A key contribution of this work is the integration of a battery system through a dual-active-bridge (DAB) converter. The DAB converter employs a multilayer perceptron (MLP) model to dynamically regulate the electrolyzer current and maintain optimal operating efficiency. An adaptive energy management strategy is further proposed to address solar irradiance fluctuations and enhance long-term operational stability. The MLP model is developed in Python and embedded into a PLECS simulation environment. The simulation results verify the effectiveness of the proposed control approach and efficiency optimization scheme. Throughout the simulation period, the PEM electrolyzer sustains an optimal efficiency of 69.9% under maximum PV power output. A limitation of this study is that the efficiency model is derived from the literature and does not yet consider all operational factors, indicating the need for refinement in future work. Full article

The development of a green hydrogen industry is a strategic priority for Russia’s energy transition, yet the dynamics of scaling up this nascent sector remain poorly understood. This study uses agent-based modeling (ABM) to simulate the co-evolution of Russia’s electricity, hydrogen, and electrolyzer sectors over 2024–2050. The model incorporates three types of heterogeneous agents (power producers, hydrogen producers, and electrolyzer manufacturers) operating under bounded rationality. Four scenarios are examined across 50 Monte Carlo runs each, varying the electrolyzer learning rate (10–25%), willingness to pay for green hydrogen (2–6 $/kg), and government support intensity. The results reveal an endogenous three-phase development pattern: Phase I (2024–2028) dominated by renewable capacity build-up reaching ~30 GW; Phase II (2029–2040) characterized by rapid electrolyzer deployment scaling to 14.5 GW; and Phase III (2041–2050) marked by stabilization at approximately 30 GW producing 1.12 Mt/year at 3.1 $/kg. Two critical thresholds are identified: renewable capacity exceeding 30–38 GW and low-cost electricity above 4–7 TWh/year. The electrolyzer learning rate emerges as the most influential parameter, while the pessimistic scenario confirms market failure without a green premium (WTP < 2 $/kg). Strategic investment losses of 2–6 billion USD are necessary catalysts for industry emergence. Russia’s 2030 production target (0.55 Mt) is found structurally infeasible under all scenarios. Full article

One of the main challenges in hydrogen production via electrolysis is the reliable measurement of the electrical work supplied. In this work, a robust electronic data acquisition system was developed to obtain precise and accurate data to evaluate the electrical work. The electrolytic concentration and electrical work were the main variables in this study. The supplied electrical energy was analyzed under both constant and pulsed voltage conditions. The results reveal that hydrogen production depends on voltage amplitude, PWM, and electrolyte concentration. The applied voltage shows a slight positive correlation with hydrogen production. PWM influences hydrogen production in the range of 0 to 1 Hz, while no significant effect is observed at higher frequencies. Electrolyte concentration has a stronger influence on hydrogen production in the range of 0.125 to 0.25 M. The optimal operating conditions were identified at 0.375 M, 1 Hz and 6 VDC, and under these conditions the hydrogen production is 0.145 mL/s and the specific energy is 165 kWh/kg. Full article

The rally to mitigate growing carbon emissions and climate change necessitates decarbonization strategies, with hydrogen emerging as a key candidate option across multiple sectors. This review examines the current state of the hydrogen economy, including production, implementation, and associated risks. Hydrogen’s versatility in industry, transportation, and energy storage is highlighted, alongside the challenges of transitioning from fossil fuel-based production. It explores the current state of hydrogen technologies, differentiating between green, blue, and gray hydrogen production methods, and highlights advancements in production techniques like thermochemical water splitting. Key findings show that while green hydrogen offers the cleanest pathway, high production costs and infrastructure limitations remain significant barriers to widespread adoption. This study also addresses safety concerns and public perception, emphasizing the need for robust risk assessment methodologies and management approaches. Furthermore, this paper underscores the importance of technological innovations, such as high-temperature electrolysis and synergies with renewable energy sources, to enhance efficiency and sustainability. Policy recommendations include financial incentives, regulatory frameworks, and international cooperation to accelerate hydrogen adoption and balance its development with other low-carbon solutions. Full article