Hydrogen, Volume 4, Issue 4 (December 2023) – 16 articles

Research into safer, durable steels to be used in hydrogen-rich environments has been gaining importance in recent years. In this work, 42CrMo4 steel was subjected to quenched and tempered heat treatments using different temperature and time durations, in order to obtain different tempered martensite microstructures. Tensile tests on smooth and notched specimens were then performed in the air as well as with in situ electrochemical hydrogen charging using two different hydrogenated conditions. The harmful effects of hydrogen are more evident in tensile tests performed on notched specimens. The harder (stronger) the steel, the more hydrogen embrittlement occurs. As the steel’s internal local hydrogen concentration rises, its strength must be gradually reduced in order to choose the best steel. The observed embrittlement differences are explained by modifications in the operative failure micromechanisms. These change from ductile (microvoid coalescence) in the absence of hydrogen, or under low hydrogen levels in the case of the softest steels, to brittle (cleavage or even intergranular fracture) under the most severe conditions. Full article

In this work, we reported the results of systematic studies of various configurations of chemically adsorbed hydrogen atoms on the surface of corrugated graphene induced by in-plane uniaxial compression. Different magnitudes of the substrate corrugations have been considered. Results of the calculations demonstrate the visible difference in the electronic structure of corrugated non-hydrogenated graphene, contrary to the absence of a visible effect of corrugation of graphene. The reciprocal effect of corrugation and local hydrogenation on the permeation of protons (H⁺) throughout the graphene membrane is also discussed. Results of the periodic DFT calculations demonstrate that binding energy between graphene and large hydrogen clusters drastically decreases with increasing the magnitudes of the corrugation graphene substrate. A similar effect of decreasing hydrogen binding energies was also observed for corrugated graphane. The obtained results can be used to control the release of hydrogen from graphene by switching mechanical stress on and off without applying additional heat. Full article

CFD modelling of compressed hydrogen fuelling provides information on the hydrogen and tank structure temperature dynamics required for onboard storage tank design and fuelling protocol development. This study compares five turbulence models to develop a strategy for cost-effective CFD simulations of hydrogen fuelling while maintaining a simulation accuracy acceptable for engineering analysis: RANS models k-ε and RSM; hybrid models SAS and DES; and LES model. Simulations were validated against the fuelling experiment of a Type IV 29 L tank available in the literature. For RANS with wall functions and blended models with near-wall treatment, the simulated average hydrogen temperatures deviated from the experiment by 1–3% with CFL ≈ 1–3 and dimensionless wall distance y⁺ ≈ 50–500 in the tank. To provide a similar simulation accuracy, the LES modelling approach with near-wall treatment requires mesh with wall distance y⁺ ≈ 2–10 and demonstrates the best-resolved flow field with larger velocity and temperature gradients. LES simulation on this mesh, however, implies a ca. 60 times longer CPU time compared to the RANS modelling approach and 9 times longer compared to the hybrid models due to the time step limit enforced by the CFL ≈ 1.0 criteria. In all cases, the simulated pressure histories and inlet mass flow rates have a difference within 1% while the average heat fluxes and maximum hydrogen temperature show a difference within 10%. Compared to LES, the k-ε model tends to underestimate and DES tends to overestimate the temperature gradient inside the tank. The results of RSM and SAS are close to those of LES albeit of 8–9 times faster simulations. Full article

Considering the mismatch between the renewable source availability and energy demand, energy storage is increasingly vital for achieving a net-zero future. The daily/seasonal disparities produce a surplus of energy at specific moments. The question is how can this “excess” energy be stored? One promising solution is hydrogen. Conventional hydrogen storage relies on manufactured vessels. However, scaling the technology requires larger volumes to satisfy peak demands, enhance the reliability of renewable energies, and increase hydrogen reserves for future technology and infrastructure development. The optimal solution may involve leveraging the large volumes of underground reservoirs, like salt caverns and aquifers, while minimizing the surface area usage and avoiding the manufacturing and safety issues inherent to traditional methods. There is a clear literature gap regarding the critical aspects of underground hydrogen storage (UHS) technology. Thus, a comprehensive review of the latest developments is needed to identify these gaps and guide further R&D on the topic. This work provides a better understanding of the current situation of UHS and its future challenges. It reviews the literature published on UHS, evaluates the progress in the last decades, and discusses ongoing and carried-out projects, suggesting that the technology is technically and economically ready for today’s needs. Full article

With growing concern about risks related to energy security around the world, the development of hydrogen cooperation between India and Japan has become very important to ensure the economic security of the two countries and to deepen economic cooperation. This study visualizes the costs and economic issues involved in transporting Ammonia from India to Japan and discusses the policy support needed to establish a hydrogen supply chain between the two countries. If Hydrogen production is conducted in Gujarat and Ammonia production is conducted using Haber–Bosch at a large-scale Ammonia plant, the price of Ammonia at the port of Tokyo can be reduced to 572 USD/mt-NH³ if highly competitive renewable energy is utilized. For evaluating the characteristics of Ammonia produced in India, high contribution to greenhouse gas reduction, low transportation risk along transportation routes, and contribution to the diversification of energy procurement in Japan should be evaluated economically, and the following five initiatives will accelerate the composition of a Hydrogen value chain between India and Japan: (1) increasing the Indian governmental support for subsidies for Hydrogen production, (2) increasing financial support to lower capital costs, (3) ensuring a business environment to lower uncertainty about future costs, (4) promoting efforts to visualize the value of carbon credits such as JCM, and (5) visualizing the value of diversification of energy procurement sources for Japan. A graphical abstract is to follow. Full article

A sustainable future hydrogen economy hinges on the development of green hydrogen and the shift away from grey hydrogen, but this is highly reliant on reducing production costs, which are currently too high for green hydrogen to be competitive. This study predicts the cost trajectory of alkaline and proton exchange membrane (PEM) electrolyzers based on ongoing research and development (R&D), scale effects, and experiential learning, consequently influencing the levelized cost of hydrogen (LCOH) projections. Electrolyzer capital costs are estimated to drop to 88 USD/kW for alkaline and 60 USD/kW for PEM under an optimistic scenario by 2050, or 388 USD/kW and 286 USD/kW, respectively, under a pessimistic scenario, with PEM potentially dominating the market. Through a combination of declining electrolyzer costs and a levelized cost of electricity (LCOE), the global LCOH of green hydrogen is projected to fall below 5 USD/kgH₂ for solar, onshore, and offshore wind energy sources under both scenarios by 2030. To facilitate a quicker transition, the implementation of financial strategies such as additional revenue streams, a hydrogen/carbon credit system, and an oxygen one (a minimum retail price of 2 USD/kgO₂), and regulations such as a carbon tax (minimum 100 USD/tonCO₂ for 40 USD/MWh electricity), and a contract-for-difference scheme could be pivotal. These initiatives would act as financial catalysts, accelerating the transition to a greener hydrogen economy. Full article

A computational study of the nitrogen purging of a solid oxide fuel cell stack enclosed in a hot box is presented. The stack operates on ammonia as a fuel, and in the case of a hydrogen leakage, the entire compartment is immediately purged with nitrogen to ensure that there are no regions with high oxygen concentrations. In addition to this, the speed at which a hydrogen leak can be detected is determined. The results are then compared to a case with a relocated nitrogen inlet. A computational fluid dynamics (CFD) model is developed using the Reynolds-averaged Navier–Stokes equations for compressible flow in combination with conservation of energy and species equations in OpenFOAM. The results suggest that for the maximum concentration of oxygen to be below 5%, the hot box should be purged for 35 s, corresponding to 1.1 kg of nitrogen, if the hot box was already heated. If the hot box was at T = 300 K, it should be purged for 95 s, corresponding to 3.0 kg of nitrogen. The purge of the heated hot box results in a heat loss of 18 kW on average. A leak could be detected in 3.2 s during open circuit voltage tests. Changing the location of the outlet does not affect the cold purge, but results in a minimum purge period of 48 s during the hot purge, and the leak could be detected in 2 s. This paper demonstrates how CFD methods can be employed in order to address questions related to hydrogen safety. Full article

In this paper, we present an updated review on the mathematical modeling of different biological methods of hydrogen production. The presented mathematical modeling and methods range from inception to the current state-of-the-art developments in hydrogen production using biological methods. A comparative study was performed along with indications for future research and shortcomings of earlier research. This review will be helpful for all researchers working on different methods of hydrogen production. However, we only covered biological methods such as biophotolysis, fermentation and microbial electrolysis cells, and this list is not exhaustive of all other methods of hydrogen production. Full article

The reversible hydrogenation/dehydrogenation of aromatic molecules, known as liquid organic hydrogen carriers, is considered as an attractive option for the safe storage and release of elemental hydrogen. The recently reported efficient synthetic routes to obtain methoxy-biphenyls in high yield make them promising candidates for hydrogen storage. In this work, a series of methoxy-substituted biphenyls and their structural parent compounds were studied. The absolute vapour pressures were measured using the transpiration method and the enthalpies of vaporisation/sublimation were determined. We applied a step-by-step procedure including structure–property correlations and quantum chemical calculations to evaluate the quality of thermochemical data on the enthalpies of phase transitions and enthalpies of formation of the studied methoxy compounds. The data sets on thermodynamic properties were evaluated and recommended for calculations in chemical engineering. A thermodynamic analysis of chemical reactions based on methoxy-biphenyls in the context of hydrogen storage was carried out and the energetics of these reactions were compared with the energetics of reactions of common LOHCs. The influence of the position of the methoxy groups in the rings on the enthalpies of the reactions relevant for hydrogen storage was discussed. Full article

Hydrogen storage is a key enabling technology for the extensive use of hydrogen as energy carrier. This is particularly true in the widespread introduction of hydrogen in car transportation. Indeed, one of the greatest technological barriers for such development is an efficient and safe storage method. So, in this tutorial review the existing hydrogen storage technologies are described with a special emphasis on hydrogen storage in hydrogen cars: the current and the ongoing solutions. A particular focus is given on solid storage and some of the recent advances on plasma hydrogen ion implantation, which should allow not only the preparation of metal hydrides, but also the imagination of a new refluing circuit. From hydrogen discovery to its use as an energy vector in cars, this review wants to be as exhaustive as possible, introducing the basics of hydrogen storage, and discussing the experimental practicalities of car hydrogen fuel. It wants to serve as a guide for anyone wanting to undertake such a technology and to equip the reader with an advanced knowledge on hydrogen storage and hydrogen storage in hydrogen cars to stimulate further researches and yet more innovative applications for this highly interesting field. Full article

Proton-conducting ceramic membranes show high hydrogen ion conductivity in the temperature range of 300–700 °C. They are attracting significant attention due to their relevant characteristics compared to both higher-temperature oxygen ion-conducting ceramic membranes and lower-temperature proton-conducting polymers. The aim of this review is to integrate the fundamentals of proton-conducting ceramic membranes with two of their relevant applications, i.e., membrane reactors (PCMRs) for methane steam reforming (SMR) and electrolysis (PCEC). Both applications facilitate the production of pure H₂ in the logic of process intensification via decarbonized heat. Firstly, an overview of various types of hydrogen production is given. The fundamentals of proton-conducting ceramic membranes and their applications in PCMRs for SMR and reversible PCEC (RePCEC), respectively, are given. In particular, RePCECs are of particular interest when renewable power generation exceeds demand because the excess electrical energy is converted to chemical energy in the electrolysis cell mode, therefore representing an appealing solution for energy conversion and grid-scale storage. Full article

Amid global energy challenges, the hydrogen evolution reaction (HER) is gaining traction for green hydrogen production. While catalyst research is ongoing, recognizing electrolyte effects remains crucial for sustainable hydrogen production via renewable-powered water electrolysis. This review delves into the intricate effects of electrolytes on the kinetics of the HER. It examines key factors including the pH, cations, anions, impurities, and electrolyte concentration. This review discusses the notion that the electrolyte pH alters catalyst–electrolyte interactions and proton concentrations, thereby influencing factors such as the hydrogen binding energy, water adsorption, and overall reaction kinetics. Moreover, this review provides a briefing on the notion that electrolyte cations such as Li⁺ can impact the HER positively or negatively, offering opportunities for improvement based on the metal substrate. Interestingly, there is a potential that the HER can be tuned using Li⁺ ions to modify the M–H bond energy, demonstrating a flexibility beyond the pH levels and counter-ions. The varied adsorption energies of metal cations on metal electrodes are also found to influence the HER kinetics. The effects of electrolyte anions and impurities are also discussed, emphasizing both the positive and negative impacts on HER kinetics. Moreover, it is pointed out that the electrolyte-engineering approach enhances the HER kinetics without permanent catalyst surface modifications. This review underscores the importance of the electrolyte composition, highlighting both the challenges and potential solutions in advancing HER research for sustainable energy production. Full article

The global interest in hydrogen as an energy carrier is steadily increasing. In this study, multiple scenarios of liquid hydrogen exports from Africa to Germany are analyzed by life cycle assessment (LCA) to quantify the global warming potential (GWP) of 1 kg hydrogen. The investigation is driven by the promise that hydrogen can be sustainably and economically produced by photovoltaic (PV)-powered electrolysis in Africa, benefiting from the geographical location near the equator and, consequently, higher solar irradiation levels. Given the absence of a pipeline network, shipping hydrogen emerges as the most efficient short-term transportation option to Germany. In this paper, supply locations—Morocco, Senegal, and Nigeria—are evaluated by means of an LCA and compared to hydrogen supply from Germany. Results show that emissions from hydrogen production and transportation by ship from Morocco range from 3.32 to 3.41 kgCO₂-eq/kgH₂. From Senegal, the range is 3.88 to 3.99 kgCO₂eq/kgH₂, and from Nigeria, it falls between 4.38 and 4.27 kgCO_2-eq/kgH₂. These emission levels are influenced by factors such as the GWP of PV electricity, the efficiency of the electrolyzer, and the transportation distance. Interestingly, the analysis reveals that PV-powered electrolysis of hydrogen in Germany, including 300 km distribution, causes, in most scenarios, a lower GWP in the range of 3.48 to 3.61 kgCO_2-eq/kgH₂ than hydrogen from the analyzed African regions. Opting for grid electricity instead of PV (with a value of 0.420 kgCO₂-eq/kWh) for hydrogen production in Germany yields a GWP ranging from 24.35 to 25.42 kgCO_2-eq/kgH₂. Hence, we can conclude that in any event, PV-powered hydrogen electrolysis has a low environmental impact not only within Africa but also in Germany. However, it is crucial to carefully consider the balance of the GWP of production versus transportation given the distance between a hydrogen production site and the location of consumption. Full article

Cancer is a leading cause of mortality worldwide. B-cells are a keystone of the adaptive immune response and are essential for the presentation of tumor-associated antigens to various types of T-cells. Approximately 1.5% of global cancer cases, including breast and gastric carcinomas and both Hodgkin’s and non-Hodgkin’s lymphomas, are linked with prior Epstein–Barr Virus (EBV) infection. Such properties make EBV-infected lymphocytes ideal models for understanding the effect of oxyhydrogen gas on dysfunctional cell cycling. The aim of this study is to assess the effects of the direct infusion of oxyhydrogen gas on the replicative capacity of EBV-immortalised B-lymphocytes. Oxyhydrogen gas was directly infused into cell culture media. Cells were incubated in 95% air and 5% CO₂ for up to 72 h. Cell enumeration was assessed with and without the addition of mitogenic growth stimuli, and subsequent cell-cycle analysis was performed. Cell enumeration: An initial trend of replicative inhibition of TK6 cells is noted with a single oxyhydrogen treatment at the 24 and 48 h time points. The daily addition of oxyhydrogen-infused media showed statistically relevant data at 24 and 48 h but not at 72 h. In mitogen-stimulated cells, a non-statistical trend of inhibition was observed at 24, 48 and 72 h. Analysis details a significant increase in DNA in the Sub G1 phase, indicating increased apoptosis. Full article

The present study compares the performance of bubbling-bed updraft and a fixed-bed downdraft gasification systems for producing hydrogen-rich (H₂) syngas from olive pomace on a semi-industrial scale. The focus is on examining the effects of temperature and efficiency ratio (ER) on the composition, low heat value (LHV), carbon conversion efficiency (CCE), and cold gas efficiency (CGE) of the produced syngas. The results presented for the fixed bed show the concentration of H₂ (15.6–16.52%), CGE (58.99–66.80%), CCE (69.07–71.86%), and LHV (4.82–5.70 MJ/Nm³). The CGE reaches a maximum of 66.80% at a temperature of 700 °C and an ER of 0.20, while the syngas yield (2.35 Nm³/kg) presents a maximum at a temperature 800 °C and an ER of 0.21, with a tendency to decrease with the increase in the temperature. For the bubbling fluidized bed, results were shown for the concentration of H₂ (12.54–12.97%), CGE (70.48–89.51%), CCE (75.83–78.49%), and LHV (6.10–6.93 MJ/Nm³), where, at a temperature of 700 °C and an ER of 0.23, the CGE is 89.51% and the LHV is 6.93 MJ/Nm³, with a tendency to decrease with the increase in the temperature, while the maximum syngas yield (2.52 Nm³/kg) occurs at a temperature of 800 °C and an ER of 0.23. Comparing the two gasification processes, the fixed bed has a higher concentration of H₂ at all the temperatures and ERs of the experiments; however, the bubbling fluidized bed has a higher CGE. These findings have implications for applications involving syngas, such as energy production and chemical synthesis, and can guide process optimization and enhance energy efficiency. The information obtained can also contribute to emission mitigation strategies and improvements in syngas-based synthesis reactors. Full article

During severe accidents in light-water nuclear reactors, the release of hydrogen poses significant risks to the integrity of the containment and the surrounding infrastructure. To address this, passive autocatalytic re-combiners (PARs) have been adopted in several countries. However, it remains challenging to eliminate the production of flammable combinations and the potential for local flame explosions, even with PARs installed. Understanding the distribution and concentration of generated hydrogen, particularly in 100% fuel-clad coolant reactions, is therefore crucial. In this study, numerical investigations using ANSYS CFX, a commercially available code, are conducted to analyze the hydrogen generation and distribution in a 1000 MWe nuclear power plant. The results show the effectiveness of PARs through a comparative evaluation of reactors with PARs and without PARs installed. The simulated scenario involved the release of hydrogen from the reactor pressure vessel, resulting in a reduction in the maximum hydrogen concentration released from 17.85% in the containment model without PARs to 9.72% in the containment model with PARs installed after 22,000 s. These findings highlight the importance of understanding and controlling the hydrogen distribution in light-water nuclear reactors during severe accidents. This study is useful in informing the mitigation risks strategy for hydrogen release in light-water nuclear reactors. Full article