Hydrogen, Volume 5, Issue 4 (December 2024) – 20 articles

It is likely that blending hydrogen into natural gas grids could contribute to economy-wide decarbonization while retaining some of the benefits that natural gas networks offer energy systems. Hydrogen injection into existing natural gas infrastructure is recognised as a key solution for energy storage during periods of low electricity demand or high variable renewable energy penetration. In this scenario, natural gas networks provide an energy vector parallel to the electricity grid, offering additional energy transmission capacity and inherent storage capabilities. By incorporating green hydrogen into the NG network, it becomes feasible to (i) address the current energy crisis, (ii) reduce the carbon intensity of the gas grid, and (iii) promote sector coupling through the utilisation of various renewable energy sources. This study gives an overview of various interchangeability indicators and investigates the permissible ratios for hydrogen blending with two types of natural gas distributed in Tunisia (ANG and MNG). Additionally, it examines the impact of hydrogen injection on energy content variation and various combustion parameters. It is confirmed by the data that ANG and MNG can withstand a maximum hydrogen blend of up to 20%. The article’s conclusion emphasises the significance of evaluating infrastructure and safety standards related to Tunisia’s natural gas network and suggests more experimental testing of the findings. This research marks a critical step towards unlocking the potential of green hydrogen in Tunisia. Full article

In this work, the results of clean hydrogen production from the direct chemical reaction between aluminum–lithium compounds and distilled water under normal conditions, without additives or catalysts, are presented. The material was prepared by mechanical alloying using a high-energy Spex-type mill in an Al20Li ratio. Relatively short milling times were programmed for the preparation of AlLi phases. Through this process, two phases (AlLi and Al8.9Li1.1) were identified, which react efficiently to produce clean hydrogen. The experiments demonstrate fast and self-sustained reactions between AlLi phases and distilled water. In both the phase preparation and hydrogen generation, 100% efficiency was achieved. The hydrolysis reaction occurred quickly, and the hydrogen volume generated was 1700 mL/g of material. Under these conditions, aluminum generates 1390 mL of hydrogen, and lithium generates 310 mL/g from both AlLi phases. A single by-product (LiAl₂(OH)₇·2H₂O) was identified. According to the results and the conditions applied in this research, the hydrogen produced does not require prior purification and can therefore be used directly in fuel cells. The AlLi–water reaction is a promising process for generating hydrogen in a simple and relatively short time compared to other hydrogen production methods. In this process, no greenhouse gas emissions were produced. Full article

The cleanliness of hydrogen energy throughout its life cycle has enabled its applications in transportation and buildings. However, such scenarios often involve the storage and use of hydrogen in enclosed spaces. Ensuring the facility’s safety during hydrogen accidental leakage through rapid detection and emergency measures has been a long-standing topic. In this work, we analyze hydrogen leakage in a hydrogen bus through CFD simulation. By extracting the hydrogen diffusion time and combining it with the leakage frequency and ignition probability, we quantitatively evaluate the placement of the sensors and propose an index for detection system assessment named the average detection delay index (ADDI). A near-field detection sensor was introduced to the system, which reduced the lower ADDI limit of the detection system by up to 10 times while reducing the system cost without changing the level of performance. Full article

Innovative and sustainable solutions are increasingly necessary as concerns about fossil fuels’ environmental and economic impacts grow. Accordingly, this study aims to enhance vehicle internal combustion engine efficiency by producing oxy-hydrogen (HHO) from drain water from the vehicle air conditioning system and utilizing it as a secondary fuel. A 1600 cc Daewoo engine equipped with electronic fuel injection was employed as the test subject. Initially, the engine’s performance was evaluated using various gasoline variants, 80, 92, and 95. The 92-octane gasoline demonstrated the highest efficiency, achieving a peak power of 113 kW and torque of 190 Nm. The engine had an 11:1 compression ratio. Then, different flow rates of oxy-hydrogen, 50, 248, 397, and 480 mL/min, generated from the air conditioner drain were combined with 92 fuel. A significant improvement was observed with the increase in the flow rate of oxy-hydrogen gas to the 92 fuel. The results indicated that incorporating 480 mL/min oxy-hydrogen gas into the fuel led to an 8.7% reduction in fuel consumption, 5.5% enhancement in thermal efficiency, and 7.9% in volumetric efficiency. Greenhouse gas emissions reductions of carbon monoxide, carbon dioxide, and hydrocarbons were recorded as 18%, 9.2%, and 9%, respectively. At the same time, nitrogen oxides increased by 12.5%. Therefore, utilizing a vehicle air conditioner drain water to generate oxy-hydrogen gas fuel in conjunction with 92-octane gasoline is an efficient solution to reduce fuel consumption, enhance energy efficiency, and mitigate the adverse effects of pollution. This approach also contributes to progress towards a more sustainable future. Full article

Enhanced photo-induced electron utilization leads to efficient photocatalytic hydrogen production. The inefficient separation of photo-induced electron–hole pairs has hindered this process. This study introduces a synergistic approach using defect-rich SnS₂ and Ti₃C₂ MXene as cocatalysts in a two-step hydrothermal process to address this challenge. By integrating these materials with TiO₂ nanosheets, we create a novel composite, SnS₂/Ti₃C₂/TiO₂ (STT), that significantly boosts photocatalytic hydrogen evolution. The defect-rich SnS₂ provides abundant active sites for hydrogen generation, while Ti₃C₂ MXene facilitates photo-induced charge separation. The synergistic combination of charge carrier diffusion enhances chromophore absorption, thereby increasing the overall photocatalytic hydrogen-production rate, achieving several grams of hydrogen per hour per gram of double cocatalysts with molybdenum vacancies. Characterization techniques confirm the phase composition of the composite (STT). Compared to pristine TiO₂ and other composites, the STT composite, optimized with a 150 °C hydrothermal treatment, shows a photocatalytic H₂-production rate nearly 192 times higher than that of pure TiO₂ and 6 times higher than that of other composites. The presence of molybdenum vacancies in SnS₂ further enhances its specific activity for hydrogen evolution by suppressing carrier recombination and providing additional active sites. Moreover, Ti₃C₂ MXene and SnS₂ act as dual cocatalysts, improving electronic conductivity and electron-transfer efficiency. Our findings demonstrate the potential of combining defect-rich SnS₂ and Ti₃C₂ MXene to develop highly efficient and sustainable photocatalysts for hydrogen production. TiO₂ has been in situ grown on highly conductive Ti₃C₂ MXene, and SnS₂, rich in molybdenum vacancies, is uniformly distributed on the TiO₂/Ti₃C₂ composite through the two-step hydrothermal method. The presence of molybdenum vacancies in SnS₂ further enhances its specific activity for hydrogen evolution by suppressing carrier recombination and providing additional active sites. Moreover, Ti₃C₂ MXene and SnS₂ act as dual cocatalysts, improving electronic conductivity and electron-transfer efficiency. Our findings demonstrate the potential of combining defect-rich SnS₂ and Ti₃C₂ MXene to develop highly efficient and sustainable photocatalysts for hydrogen production. Full article

Novel multicomponent Nb–Ni–Ti–Zr–Co alloys with 20–55 at.% Nb were synthesized from metal powders by arc melting. The resulting alloys consist primarily of Nb-rich and eutectic body-centered (BCC) phases. The content of the eutectic BCC phase is highest for an equimolar composition, while the content of the Nb-rich BCC phase increases with Nb content in the alloy. The content of secondary phases is the highest for the alloy with 32 at.% Nb. According to ab initio calculations, hydrogen occupies tetrahedral interstitial sites in the Nb-rich phase and octahedral sites in the eutectic BCC phase. For different Nb concentrations, hydrogen-binding energies were calculated. An increase in the Nb-rich phase leads to softening of multicomponent alloys. The alloys with 20 and 32 at.% Nb demonstrate high hydrogen permeability (1.05 and 0.96 × 10⁻⁸ molH₂m⁻¹s⁻¹Pa^−0.5, respectively) at 400 °C, making them promising for hydrogen purification membrane application. Multicomponent alloys with a high Nb content (55 at.%) have low resistance to hydrogen embrittlement. Full article

Future decarbonized applications that rely on renewable and carbon-dioxide-neutral hydrogen production could benefit from the gasification of waste to produce hydrogen. In the current study, an Aspen Plus^® model was developed by coupling a co-gasification model to a water–gas shift (WGS) model. The feedstock employed in the simulations was a blend of municipal solid waste (MSW) and biomass from Morocco. A parametric assessment was conducted to analyze the effect of the steam-to-feedstock ratio (SFR) on the syngas composition and the WGS reactor temperature. This study also presents a comparison between the results of the gasification process before and after the WGS reactor, using air and steam as the gasifying agent. The results show an increase in hydrogen volumetric percentage for higher steam-to-feedstock ratios in the gasifier. Moreover, the inclusion of a WGS reactor enhances hydrogen and carbon dioxide while reducing the amount of carbon monoxide in the syngas for both air and steam as the gasifying agents. It can be concluded that a co-gasification process can be intensified by coupling it to a WGS reactor without steam injection to produce hydrogen-rich syngas with reduced operational expenditures. Full article

As one of the most promising clean energy sources, hydrogen power has gradually emerged as a viable alternative to traditional energy sources. However, hydrogen safety remains a significant concern due to the potential for explosions and the associated risks. This review systematically examines hydrogen explosions, with a focus on high-pressure and low-temperature storage, transportation, and usage processes mostly based on the published papers from 2020. The fundamental principles of hydrogen explosions, classifications, and analysis methods, including experimental testing and numerical simulations, are explored. Key factors influencing hydrogen explosions are also discussed. The safety issues of hydrogen power on railway applications are focused, and finally, recommendations are provided for the safe application of hydrogen power in railway transportation, particularly for long-distance travel and heavy-duty freight trains, with an emphasis on storage safety considerations. Full article

Catalytic activity, mechanisms, and active sites were determined for methane steam reforming (MSR) over gadolinium-doped ceria (GDC) supported iridium (0.1 wt%) prepared by impregnation of GDC with iridium acetylacetonate. Isothermal steady-state rate measurements followed by micro-gas chromatography analysis were performed at 660 and 760 °C over Ir/GDC samples pretreated in N₂ or H₂ at 900 °C. Transient responses to CH₄ or H₂O step changes in isothermal conditions were carried out at 750 °C over Ir/GDC pretreated in He or H₂ using online quadrupole mass spectrometry. In the proposed mechanism, Ir/GDC proceeds through a dual-type active site associating, as follows: (i) Ir metallic particles surface as active sites for the cracking of CH₄ into reactive C species, and (ii) reducible (Ce⁴⁺) sites at GDC surface responsible for a redox mechanism involving Ce⁴⁺/Ce³⁺ sites, being reduced by reaction with reactive C into CO (or CO₂) depending on the oxidation state of GDC and re-oxidized by H₂O. Full reduction of reducible oxygen species is possible with CH₄ after He treatment, whereas only 80% is reached in CH₄ after H₂ treatment. Full article

This study presents the synthesis and characterization of novel sulfamethoxazole organotin complexes and evaluates their potential for hydrogen storage applications. The synthesized complexes were characterized using various techniques, such as Nuclear Magnetic Resonance and Fourier Transform Infrared spectroscopy to determine their constructional and physicochemical properties. Field Emission Scanning Electron Microscopy was applied to analyze the surface morphology, and the Brunauer–Emmett–Teller method was utilized to measure the surface area. High-pressure adsorption experiments demonstrated the remarkable hydrogen storage capabilities of these complexes, with the highest hydrogen uptake of 29.1 cm³/g observed at 323 K. The results suggest that the prepared sulfamethoxazole organotin complexes have the potential to be candidates for gas separation and storage applications. Full article

To expedite the development of the infrastructural expansion for hydrogen applications, the research project “THEWA” was founded. Within this project, the development of hydrogen-refueling stations is being advanced so that the hydrogen strategy for mobility in Germany can move forward. One development point of the project is to develop an evaluation model that recommends a concept for hydrogen-refueling stations for initial individual situations. In this work, an evaluation method is developed that provides an appropriate recommendation. For this purpose, basics, such as the general structure of hydrogen-refueling stations, their classification into functional areas, and already-existing evaluation methods for multi-criteria decisions, are shown. The method for the evaluation of hydrogen-refueling stations will be developed in a component-based manner, for which a selection of influencing factors of hydrogen-refueling stations will be explained and categorized. With the help of an expert workshop, these are scaled so that the result is an evaluation method based on an expert assessment and the consideration of individual customer requirements. In addition, the method is implemented in a tool so that it can be used more easily. Full article

This study addresses the growing need for effective energy management solutions in university settings, with particular emphasis on solar–hydrogen systems. The study’s purpose is to explore the integration of deep learning models, specifically MobileNetV2 and InceptionV3, in enhancing fault detection capabilities in AIoT-based environments, while also customizing ISO 50001:2018 standards to align with the unique energy management needs of academic institutions. Our research employs comparative analysis of the two deep learning models in terms of their performance in detecting solar panel defects and assessing accuracy, loss values, and computational efficiency. The findings reveal that MobileNetV2 achieves 80% accuracy, making it suitable for resource-constrained environments, while InceptionV3 demonstrates superior accuracy of 90% but requires more computational resources. The study concludes that both models offer distinct advantages based on application scenarios, emphasizing the importance of balancing accuracy and efficiency when selecting appropriate models for solar–hydrogen system management. This research highlights the critical role of continuous improvement and leadership commitment in the successful implementation of energy management standards in universities. Full article

The process of dry reforming methane (DRM) is seen as a viable approach for producing hydrogen and lowering the atmospheric concentration of carbon dioxide. Recent times have witnessed notable advancements in the development of catalysts that enable this pathway. Numerous experiments have been conducted to investigate the use of nickel-based catalysts in the dry reforming of methane. All these reported experiments showed that variations in the catalyst property, namely pore size, pore volume, and surface area, affect the hydrogen production in DRM. None of the previous studies has modeled the surface nickel-incorporated catalyst activity based on its properties. In this research, DRM’s hydrogen yield is predicted using three different artificial neural network-learning algorithms as a function of the physical properties of Ni-based catalyst along with two reaction inputs. The geometric properties as an input set are a different approach to developing such empirical models. The best-fitting models are the artificial neural network model using the Levenberg–Marquardt algorithm and ten hidden neurons, which gave a coefficient of determination of 0.9931 and an MSE of 7.51, and the artificial neural network model using the scaled conjugate gradient algorithm and eight hidden layer neurons, which had a coefficient of determination of 0.9951 and an MSE of 4.29. This study offers useful knowledge on how to improve the DRM processes. Full article

The hydrogen evolution reaction (HER) in the renewable energy system has gained a lot of attention from researchers as hydrogen is assumed to be a clean and renewable carrier. Transition metals and their compounds have been used as promising alternatives to precious noble metals for the HER, offering low cost, more availability, and high activity. In this work, we discussed the mechanisms of the HER and how morphology influenced the catalytic performance of transition metal disulfide (TMD), focusing on structures that range from zero-dimensional (0D) to three-dimensional (3D) TMD materials. Notably, two-dimensional (2D) TMDs, like nanosheets, exhibit the lowest overpotential and a very small Tafel slope, which can be ascribed to their inherent layered structure and large surface area. According to recent research reports, the efficacy and efficiency of the HER process are influenced by surface chemistry, electrochemical characteristics, and the existence of active sites. Full article

Hydrogen production is essential in the transition to sustainable energy. This study examines two hydrogen production routes, steam methane reforming (SMR) and chemical looping reforming (CLR), both using raw natural gas as feedstock. SMR, the most commonly used industrial process, involves reacting methane with steam to produce hydrogen, carbon monoxide, and carbon dioxide. In contrast, CLR uses a metal oxide as an oxygen carrier to facilitate hydrogen production without generating additional carbon dioxide. Simulations conducted using Aspen HYSYS analyzed each method’s performance and energy consumption. The results show that SMR achieved 99.98% hydrogen purity, whereas CLR produced 99.97% purity. An energy analysis revealed that CLR requires 31% less energy than SMR, likely due to the absence of low- and high-temperature water–gas shift units. Overall, the findings suggest that CLR offers substantial advantages over SMR, including lower energy consumption and the production of cleaner hydrogen, free from carbon dioxide generated during the water–gas shift process. Full article

Geological hydrogen storage, seen as a viable solution for addressing energy demands and mitigating the intermittency of wind power, is gaining recognition. At present, there are no specific studies that estimate hydrogen storage capacity and the potential for wind integration in North Dakota despite the state’s enormous energy resources and capabilities. The study’s key innovation lies in repurposing a region historically associated with oil and gas for sustainable energy storage, thereby addressing the intermittency of wind sources. Moreover, the innovative aspect of this study involves field selection, site screening, characterization, and mathematical modeling to simulate a wind–hydrogen production and geological storage system. A 15 MW wind farm, using real-world data from General Electric wind turbines, is employed to assess storage capacities within the Middle Bakken formation. The study reveals substantial storage potentials in wells W24814, W19693, and W26990, with capacities of 54,000, 33,000, and 22,000 tons, respectively. These capacities translate to energy storage capabilities of 1080, 660, and 440 GWh, with minimum storage durations of 140, 80, and 57 days, respectively, under a 60% system efficiency. By pioneering the integration of wind energy with geological hydrogen storage in a region traditionally dominated by fossil fuel extraction, this research could play a crucial role in advancing North Dakota’s energy transition, providing a blueprint for similar initiatives globally. Full article

The International Maritime Organization (IMO) sets ambitious greenhouse gas reduction targets for the maritime industry. From a long-term net zero emission perspective, ammonia fuel is expected to play a significant role in the marine decarbonization journey compared to LNG as a transition fuel. Also, in addition to internal combustion engine applications, solid oxide fuel cells (SOFCs) have gained more attention in marine propulsion applications due to their high efficiency. This study was performed to investigate the technical feasibility of utilizing a closed-loop SOFC thermal energy release for ammonia decomposition, leading to hydrogen fuel generation and subsequently feed back into SOFCs. The result proves that the integrated system of ammonia cracking SOFCs can maintain a self-balanced condition, ensuring adequate SOFC heat supply for the ammonia cracking process to produce hydrogen while supporting normal SOFC operation and generating heat. This paper concludes that an integrated system represents a novel and feasible solution and emphasizes its potential as an adaptable solution for future marine applications. Full article

Concerns over the life cycle impacts of fluoropolymers have led to their inclusion in broad product restriction proposals for per- and poly-fluorinated alkyl substances (PFAS), despite their non-bioavailable properties and low exposure potential in complex, durable goods such as non-consumer electrical products. Based on the hypothesis that manufacturers are most able to manage the environmental impacts of their products, practical engineering approaches to implementing life cycle fluoropolymer stewardship are evaluated to bridge the ongoing debate between precautionary and risk-based approaches to PFAS management. A life cycle thinking approach is followed that considers product design and alternatives, as well as the product life cycle stages of material sourcing, manufacturing, field deployment, and end-of-life. Over the product life cycle, the material sourcing and end-of-life stages are most impactful in minimizing potential life cycle PFAS emissions. Sourcing fluoropolymers from suppliers with fluorosurfactant emissions control and replacement minimizes the potential emissions of bio-available PFAS substances. A stack-as-service approach to electrolyzer operations ensures a takeback mechanism for the recycling of end-of-life fluoropolymer materials. Retaining electrolytic hydrogen’s license to operate results in over USD 2 of environmental and health benefits per kilogram of hydrogen produced from reduced greenhouse gas and air pollutant emissions compared to conventional hydrogen production via steam methane reforming. Full article

A comprehensive 3D Multiphysics model was developed to simulate a plate fin heat exchanger designed for hydrogen liquefaction, incorporating an ortho-para hydrogen conversion catalyst in the hot fin channel. The model encompassed the 3D serrate fin structure, turbulent flow within the cold fin channel, and porous flow through the catalytic hot fin channel. Species transportation within the hot fin channel is coupled with ortho-para hydrogen conversion kinetics, while heat transfer mechanisms between the hot and cold fin channels are rigorously accounted for. Additionally, the state-of-the-art equation of state is employed to accurately describe the thermodynamic properties of ortho- and para-hydrogen within the model. Numerous operational parameters, including the gas hourly space velocity, cold gas velocity, ortho-para hydrogen conversion kinetics, and operating pressure, were systematically varied to identify the kinetic and heat transfer constraints during the heat exchanger operation. The findings revealed that the ortho-para hydrogen conversion kinetic parameter predominantly governs operations requiring high gas hourly space velocity, particularly in large-scale hydrogen liquefaction processes. Furthermore, a significant pressure drop within the catalytic filled channel was observed; however, operating at higher pressure mitigates this issue while mildly enhancing ortho-para hydrogen conversion kinetics. Full article

Magnesium hydride solids doped with transition metals have received attention recently as prospective hydrogen storage materials for a green energy source and a hydrogen economy. In this study, MgTiH_n (n = 1–20) clusters were investigated for the first time by employing the B3PW91 hybrid density functional theory computational chemistry technique with all electron basis sets to determine precise cluster structures and the maximum hydrogen capacity for this model system. We find that hydrogen atoms bind to the metal cluster core until a MgTiH₁₄ saturation limit is reached, with hydrogen dissociation from this system occurring for MgTiH₁₅ and larger cluster sizes. This MgTiH₁₄ cluster contains a large 16.4% hydrogen by mass. This saturation size limit and hydrogen mass percent is larger than the analogous MgScH_n system previously reported. The clusters relative stabilities and electronic properties are discussed along with a possible novel hydrogen dissociation pathway. MgTiH₁₀ and MgTiH₁₃ clusters are predicted to be especially stable species in this size range. Full article