Hydrogen, Volume 5, Issue 3 (September 2024) – 14 articles

Aromatic esters such as phenyl acetates are of interest as promising liquid organic hydrogen carriers (LOHCs) due to the presence of double bonds. However, the key factor for the development of green hydrogen fuel is the production of LOHCs from renewable sources. Since the synthesis and isolation of such esters is a complex task, understanding the relationship between the chemical structures of aromatic esters and their thermodynamic properties is of great importance for their further practical use as LOHCs. Obtaining reliable thermodynamic and thermochemical properties of phenyl and benzyl phenyl acetates formed the basis of this work. Vapour pressures, enthalpies of vaporisation, and enthalpies of formation were systematically studied. An approach based on the structure–property correlation was used to confirm these quantities. Additionally, the high-level quantum-chemical method G4 was used to estimate the enthalpy of formation in the gas phase. The final stage was the assessment of the energetics of chemical reactions based on aromatic esters and their partially and fully hydrogenated analogues. Full article

A one-dimensional computational model has been developed that can be used to identify operating conditions for the cathode side of a proton exchange membrane fuel cell such that both the inlet and outlet relative humidity is equal to 100%. By balancing the calculated pressure drop along the cathode side flow channel with the change in molar composition, inlet conditions for the cathode side can be identified with the goal of avoiding channel flooding. The channel length, height, width and the land-to-channel width ratio are input parameters for the model so that it might be used to dimension the cathode flow field. The model can be used to calculate the limiting current density, and we are presenting unprecedented high values as a result of the high pressure drop along the flow channels. Such high current densities can ultimately result in a fuel cell power density beyond the typical value of 1.0–2.0 W/cm² for automotive fuel cells. Full article

This review sets out to investigate the detrimental impacts of hydrogen gas (H₂) on critical boiler components and provide appropriate state-of-the-art mitigation measures and future research directions to advance its use in industrial boiler operations. Specifically, the study focused on hydrogen embrittlement (HE) and high-temperature hydrogen attack (HTHA) and their effects on boiler components. The study provided a fundamental understanding of the evolution of these damage mechanisms in materials and their potential impact on critical boiler components in different operational contexts. Subsequently, the review highlighted general and specific mitigation measures, hydrogen-compatible materials (such as single-crystal PWA 1480E, Inconel 625, and Hastelloy X), and hydrogen barrier coatings (such as TiAlN) for mitigating potential hydrogen-induced damages in critical boiler components. This study also identified strategic material selection approaches and advanced approaches based on computational modeling (such as phase-field modeling) and data-driven machine learning models that could be leveraged to mitigate potential equipment failures due to HE and HTHA under elevated H₂ conditions. Finally, future research directions were outlined to facilitate future implementation of mitigation measures, material selection studies, and advanced approaches to promote the extensive and sustainable use of H₂ in industrial boiler operations. Full article

Liquid hydrogen is a promising energy carrier in the global hydrogen value chain with the advantages of high volumetric energy density/purity, low operating pressure, and high flexibility in delivery. Safe and high-efficiency storage and transportation are essential in the large-scale utilization of liquid hydrogen. Aiming at the two indicators of the hold time and normal evaporation rate (NER) required in standards, this paper focuses on the thermal behaviors of fluid during the no-vented storage of liquid hydrogen and thermal insulations applied for the liquid hydrogen tanks, respectively. After presenting an overview of experimental/theoretical investigations on thermal behaviors, as well as typical forms/testing methods of performance of thermal insulations for liquid hydrogen tanks, seven perspectives are proposed on the key challenges and recommendations for future work. This work can benefit the design and improvement of high-performance LH₂ tanks. Full article

Hydrogen (H₂) storage is one of the most problematic issues regarding the widespread use of hydrogen, and solid-state hydrogen storage materials are promising in this regard. Hydrogen storage by sodium borohydride (NaBH₄) takes attention with its advantages and idiosyncratic properties. In this study, potentials and challenges of sodium borohydride are evaluated considering storage conditions, safety, hydrogen purity, storage capacity, efficiency, cost, and the maturity. Moreover, marine use of NaBH₄ is demonstrated, and the pros and cons of the NaBH₄ hydrogen storage method are stated. According to evaluations, whereas advantages can be sorted as fuel availability, fuel recyclability, mild storage conditions, exothermicity of reaction, pressure flexibility, and H₂ purity, challenges can be sorted as high costs, catalyst deactivation, regeneration, and practical/technical implementation issues. The great potential of NaBH₄ marine use (against road/aerial vehicles) is water availability, no need to carry all the required water for the entire journey, and reduced system weight/volume by this way. Full article

The transition to cleaner energy sources, particularly in hard-to-abate industrial sectors, often requires the gradual integration of new technologies. Hydrogen, crucial for decarbonization, is explored as a fuel in blended combustions. Blending or replacing fuels impacts combustion stability and heat transfer rates due to differing densities. An extensive literature review examines blended combustion, focusing on hydrogen/methane mixtures. While industrial burners claim to accommodate up to 20% hydrogen, theoretical support is lacking. A novel thermodynamic analysis methodology is introduced, evaluating methane/hydrogen combustion using the Wobbe index. The findings highlight practical limitations beyond 25% hydrogen volume, necessitating a shift to “totally hydrogen” combustion. Blended combustion can be proposed as a medium-term strategy, acknowledging hydrogen’s limited penetration. Higher percentages require burner and infrastructure redesign. Full article

The maritime industry is a major source of greenhouse gas (GHG) emissions, largely due to ships running on fossil fuels. Transitioning to hydrogen-powered marine transportation in the Mediterranean Sea requires the development of a network of hydrogen refueling stations across the region to ensure a steady supply of green hydrogen. This paper explores the technoeconomic viability of harnessing wave energy from the Mediterranean Sea to produce green hydrogen for hydrogen-powered ships. Four promising island locations—near Sardegna, Galite, Western Crete, and Eastern Crete—were selected based on their favorable wave potential for green hydrogen production. A thorough analysis of the costs associated with wave power facilities and hydrogen production was conducted to accurately model economic viability. The techno-economic results suggest that, with anticipated cost reductions in wave energy converters, the levelized cost of hydrogen could decrease to as low as 3.6 €/kg, 4.3 €/kg, 5.5 €/kg, and 3.9 €/kg for Sardegna, Galite, Western Crete, and Eastern Crete, respectively. Furthermore, the study estimates that, in order for the hydrogen-fueled ships to compete effectively with their oil-fueled counterparts, the levelized cost of hydrogen must drop below 3.5 €/kg. Thus, despite the competitive costs, further measures are necessary to make hydrogen-fueled ships a viable alternative to conventional diesel-fueled ships. Full article

H₂ is considered a practical substitute for fossil fuels, especially for transportation by road and air, created either from fossil fuels or through the process of electrolysis of water. Research questions were included based on numerous research and the analysis of articles. The cost analysis of H₂ processes, techno-economic hurdles in commercialization, and the economic comparison of various H₂-production methods were the basis for the study of papers. The current research examines the different methods of thermochemical, biological, and electrochemical processes utilized in converting biomass into hydrogen. The benefits, constraints, and significant enhancements of every procedure are outlined. The examination assesses the cost of production, the level of technology readiness, and the potential for scalability. Thermochemical techniques, such as gasification and steam reforming, are effective at producing hydrogen. Steam gasification is perfect for moist and dry biomass in the absence of an oxidizing agent. Dark fermentation is more efficient for biological conversion because it requires less energy. Moreover, the electrochemical procedure is viable for biomass. Thermochemical treatment is significantly more advanced than biological or electrochemical treatment when it comes to scaling opportunities based on comparisons of current processes. The results of this research show that biomass–hydrogen processes have the potential for increasing H₂ production, but further enhancements are needed to produce larger quantities for competitiveness. Full article

Sustainable technologies to replace current fossil solutions are essential to meet future CO₂ emission reduction targets. Therefore, this paper compares key performance indicators of a hydrogen- and a methane-flame-fired crucible furnace with computational fluid dynamics simulations at identical firing powers, aiming to fully decarbonize the process. Validated numerical models from the literature were used to compare temperatures, radiation fields, radiation parameters and heat transfer characteristics. As a result, we observed higher combustion temperatures and a 19.0% higher fuel utilization rate in the hydrogen case, indicating more efficient operating modes, which could be related to the increased radiant heat flux and temperature ranges above 1750 K. Furthermore, higher scattering of the heat flux distribution on the crucible surface could be determined indicating more uneven melt bath temperatures. Further research could focus on quantifying the total fuel consumption required for the heating up of the furnace, for which a transient numerical model could be developed. Full article

This paper investigated the opportunities and challenges of integrating ports into hydrogen (H₂) supply chains in the context of Australia and Japan because they are leading countries in the field and are potential leaders in the upcoming large-scale H₂ trade. Qualitative interviews were conducted in the two countries to identify opportunities for H₂ ports, necessary infrastructure and facilities, key factors for operations, and challenges associated with the ports’ development, followed by an online survey investigating the readiness levels of H₂ export and import ports. The findings reveal that there are significant opportunities for both countries’ H₂ ports and their respective regions, which encompass business transition processes and decarbonisation. However, the ports face challenges in areas including infrastructure, training, standards, and social licence, and the sufficiency and readiness levels of port infrastructure and other critical factors are low. Recommendations were proposed to address the challenges and barriers encountered by H₂ ports. To optimise logistics operations within H₂ ports and facilitate effective integration of H₂ applications, this paper developed a user-oriented working process framework to provide guidance to ports seeking to engage in the H₂ economy. Its findings and recommendations contribute to filling the existing knowledge gap pertaining to H₂ ports. Full article

This study proposes a combination system consisting of a biogas dry reforming reactor and a solid oxide fuel cell (SOFC). Since biogas dry reforming is an endothermic reaction, this study adopted a membrane reactor operated due to the non-equilibrium state with H₂ separation from the reaction space. This study aimed to clarify the performance of the Ni/Cr/Ru catalyst using a biogas dry reforming membrane reactor. Additionally, this study also undertook a comparison of the performance of the Ni/Cr/Ru catalyst with that of the Ni/Cr catalyst. The impact of operation temperature, the molar ratio of CH₄:CO₂, the differential pressure between the reaction chamber and the sweep chamber, and the introduction of a sweep gas on the performance of the biogas dry reforming membrane reactor using a Pd/Cu membrane and a Ni/Cr/Ru catalyst was examined. The concentration of H₂ using the Ni/Cr/Ru catalyst was greater than that using the Ni/Cr catalyst by 2871 ppmV for the molar ratio of CH₄:CO₂ = 1.5:1 at the reaction temperature of 600 °C and the differential pressure of 0 MPa without a sweep gas in particular. Under this condition, CH₄ conversion, H₂ yield, and thermal efficiency were 67.4%, 1.77 × 10⁻²%, and 0.241%, respectively. Full article

Poly(vinyl acetate) nanofibers doped with PdS-ZnS nanoparticles (PdS-ZnS/PVAc nanofibers) were fabricated via an electrospinning technique. PdS-ZnS nanoparticles were in situ synthesized by adding (NH₄)₂S solution to poly(vinyl acetate)/zinc acetate/palladium acetate solution. Electrospinning of the formed colloidal solution led to the formation of poly(vinyl acetate) nanofibers containing uniformly distributed PdS-ZnS nanoparticles. The prepared samples were characterized by field emission scanning electron microscopy, X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy. In photocatalytic activity investigation, the PdS-ZnS/PVAc nanofibers showed remarkably enhanced performance towards water photosplitting under solar irradiation compared to the ZnS/PVAc nanofibers. This enhanced performance is attributed to the synergistic effects of heterostructured PdS-ZnS nanoparticles, which can improve photogenerated charge migration and solar light absorption. Full article

As part of the ongoing transition from fossil fuels to renewable energies, advances are particularly expected in terms of safe and cost-effective solutions. Publicising instances of such advances and emphasising global safety considerations constitute the rationale for this communication. Knowing that high-strength steels can prove economically relevant in the foreseeable future for transporting hydrogen in pipelines by limiting the pipe wall thickness required to withstand high pressure, one advance relates to a bench designed to assess the safe transport or renewable-energy-related buffer storage of hydrogen gas. That bench has been implemented at the technology readiness level TRL 6 to test initially intact, damaged, or pre-notched 500 mm-long pipe sections with nominal diameters ranging from 300 to 900 mm in order to appropriately validate or question the use of reputedly satisfactory predictive models in terms of hydrogen embrittlement and potential corollary failure. The other advance discussed herein relates to the reactivation of a previously fruitful applied research into safe mass solid-state hydrogen storage by magnesium hydride through a new public–private partnership. This latest development comes at a time when markets have started driving the hydrogen economy, bearing in mind that phase-change materials make it possible to level out heat transfers during the absorption/melting and solidification/desorption cycles and to attain an overall energy efficiency of up to 80% for MgH₂-based compacts doped with expanded natural graphite. Full article

The local binding and migration behavior of the proton defect in cubic yttria-stabilized zirconia (YSZ) is studied by first-principles calculations and muon-spin spectroscopy (μSR) measurements. The calculations are based on density-functional theory (DFT) supplemented with a hybrid-functional approach with the proton defect embedded in quasi-random supercells of 10.3 mol% yttria content, where the yttrium–zirconium substitutional defects are charge compensated by oxygen vacancies. Representative migration pathways for the proton comprising both transfer and bond reorientation modes are analysed and linked to the underlying microstructure of the YSZ lattice. The μSR data show the evolution of the diamagnetic fraction corresponding to the muon-isotope analogue with an activation energy of diffusion equal to 0.17 eV. Comparisons between the calculations and the experiment allow an assessment of the character of the short-range migration of the proton particle in cubic YSZ. Full article