Hydrogen, Volume 5, Issue 1 (March 2024) – 9 articles

This study uses plane wave density functional theory (DFT) to investigate the effect of certain metal carbides (Niobium carbide, Vanadium carbide, Titanium carbide, and Manganese sulfide) on hydrogen embrittlement in pipeline steels. Our results predict that the interaction of hydrogen molecules with these metal carbides occurs in the long range with binding energy varying in the energy window [0.043 eV to 0.70 eV].In addition, our study shows the desorption of H₂ molecules from these metal carbides in the chemisorptions. Since atomic state hydrogen interacts with NbC, VC, TiC, and MnS to cause embrittlement, we classified the strength of the hydrogen trapping as TiC + H > VC + H > NbC + H> MnS + H. In addition, our study reveals that the carbon site is a more favorable hydrogen-trapping site than the metal one. Full article

High-entropy alloys (HEAs) are a promising class of materials that can grant remarkable functional performances for a large range of applications due to their highly tunable composition. Among these applications, recently, bcc HEAs capable of forming fcc hydrides have been proposed as high-capacity hydrogen storage materials with improved thermodynamics compared to classical metal hydrides. In this context, a single-phase bcc (TiVNb)_0.90Cr_0.05Mn_0.05 HEA was prepared by arc melting to evaluate the effect of combined Cr/Mn addition in the ternary TiVNb. A thermodynamic destabilization of the fcc hydride phase was found in the HEA compared to the initial TiVNb. In situ neutron and synchrotron X-ray diffraction experiments put forward a fcc → bcc phase transition of the metallic subnetwork in the temperature range of 260–350 °C, whereas the H/D subnetwork underwent an order → disorder transition at 180 °C. The absorption/desorption cycling demonstrated very fast absorption kinetics at room temperature in less than 1 min with a remarkable total capacity (2.8 wt.%) without phase segregation. Therefore, the design strategy consisting of small additions of non-hydride-forming elements into refractory HEAs allows for materials with promising properties for solid-state hydrogen storage to be obtained. Full article

The present paper offers a thorough examination of the safety measures enforced at hydrogen filling stations, emphasizing their crucial significance in the wider endeavor to advocate for hydrogen as a sustainable and reliable substitute for conventional fuels. The analysis reveals a wide range of crucial safety aspects in hydrogen refueling stations, including regulated hydrogen dispensing, leak detection, accurate hydrogen flow measurement, emergency shutdown systems, fire-suppression mechanisms, hydrogen distribution and pressure management, and appropriate hydrogen storage and cooling for secure refueling operations. The paper therefore explores several aspects, including the sophisticated architecture of hydrogen dispensers, reliable leak-detection systems, emergency shut-off mechanisms, and the implementation of fire-suppression tactics. Furthermore, it emphasizes that the safety and effectiveness of hydrogen filling stations are closely connected to the accuracy in the creation and upkeep of hydrogen dispensers. It highlights the need for materials and systems that can endure severe circumstances of elevated pressure and temperature while maintaining safety. The use of sophisticated leak-detection technology is crucial for rapidly detecting and reducing possible threats, therefore improving the overall safety of these facilities. Moreover, the research elucidates the complexities of emergency shut-off systems and fire-suppression tactics. These components are crucial not just for promptly managing hazards, but also for maintaining the station’s structural soundness in unanticipated circumstances. In addition, the study provides observations about recent technical progress in the industry. These advances effectively tackle current safety obstacles and provide the foundation for future breakthroughs in hydrogen fueling infrastructure. The integration of cutting-edge technology and materials, together with the development of upgraded safety measures, suggests a positive trajectory towards improved efficiency, dependability, and safety in hydrogen refueling stations. Full article

Hydrogen is a versatile energy vector for a plethora of applications; nevertheless, its production from waste/residues is often overlooked. Gasification and subsequent conversion of the raw synthesis gas to hydrogen are an attractive alternative to produce renewable hydrogen. In this paper, recent developments in R&D on waste gasification (municipal solid waste, tires, plastic waste) are summarised, and an overview about suitable gasification processes is given. A literature survey indicated that a broad span of hydrogen relates to productivity depending on the feedstock, ranging from 15 to 300 g H₂/kg of feedstock. Suitable gas treatment (upgrading and separation) is also covered, presenting both direct and indirect (chemical looping) concepts. Hydrogen production via gasification offers a high productivity potential. However, regulations, like frame conditions or subsidies, are necessary to bring the technology into the market. Full article

The Paris Agreement aims to limit global warming, and one of the most polluting sectors is heavy industry, where cement production is a significant contributor. This work briefly explores some alternatives, recycling, reducing clinker content, waste heat recovery, and carbon capture, discussing their advantages and drawbacks. Then, it examines the economic viability and benefits of increasing oxygen concentration in the primary burning air from 21 to 27 vol.%, which could improve clinker production by 7%, and the production of hydrogen through PEM electrolysis to make up 5% of the fuel thermal fraction, considering both in a cement plant producing 3000 tons of clinker per day. This analysis used reference values from Secil, an international company for cement and building materials, to determine the required scale of the oxygen and hydrogen production, respectively, and calculate the CAPEX of each approach. It is concluded that oxygen enrichment can provide substantial fuel savings for a relatively low cost despite a possible significant increase in NO_x emissions. However, hydrogen production at this scale is not currently economically viable. Full article

This review paper reports on the use of Delafossite as a layer between perovskite-based solar cells to improve hydrogen production efficiency and make the process easier. The investigation delves into the possible breakthroughs in sustainable energy generation by investigating the synergistic interplay between Delafossite and solar technology. This investigation covers copper-based Delafossite material’s properties, influence on cell performance, and function in the electrolysis process for hydrogen production. Some reports investigate the synthesis and characterizations of delafossite materials and try to improve their performance using photo electrochemistry. This work sheds light on the exciting prospects of Delafossite integration using experimental and analytical methodologies. Full article

The effect of the partial substitution of Cr with Fe on the thermodynamic parameters of vanadium-rich Ti₁₆V₆₀Cr_24-xFe_x alloys (x = 0, 4, 8, 12, 16, 20, 24) was investigated. For each composition, a pressure–concentration isotherm (PCI) was registered at 298, 308, and 323 K. The PCI curves revealed a reduction in plateau pressure and a decrease in desorbed hydrogen capacity with an increasing amount of Fe. For all alloys, about 50% or less of the initial hydrogen capacity was desorbed for all chosen temperatures. Entropy (ΔS) and enthalpy (ΔH) values were deducted from corresponding Van’t Hoff plots of the PCI curves: the entropy values ranged from −150 to −57 J/K·mol H₂, while the enthalpy values ranged from −44 to −21 kJ/mol H₂. They both decreased with an increasing amount of Fe. Plotting ΔS as function of ΔH showed a linear variation that seems to indicate an enthalpy–entropy compensation. Moreover, a quality factor analysis demonstrated that the present relationship between entropy and enthalpy is not of a statistical origin at the 99% confidence level. Full article

Hydrogen can become a prevalent renewable fuel in the future green economy, but technical and economic hurdles associated with handling hydrogen must be overcome. To store and transport hydrogen in an energy-dense liquid form, very cold temperatures, around 20 K, are required. Evaporation affects the achievable mass flow rate during the high-speed transfer of hydrogen at large pressure differentials, and accurate prediction of this process is important for the practical design of hydrogen transfer systems. Computational fluid dynamics modeling of two-phase hydrogen flow is carried out in the present study using the volume-of-fluid method and the Lee relaxation model for the phase change. Suitable values of the relaxation time parameter are determined by comparing numerical results with test data for high-speed two-phase hydrogen flows in a configuration involving a tube with sudden expansion, which is common in practical systems. Simulations using a variable outlet pressure are conducted to demonstrate the dependence of flow rates on the driving pressure differential, including the attainment of the critical flow regime. Also shown are computational results for flows with various inlet conditions and a fixed outlet state. Field distributions of the pressure, velocity, and vapor fractions are presented for several flow regimes. Full article

Recent studies have demonstrated how a material based on Mn oxide, supported by a polymeric matrix, shows an interesting H₂ absorption capacity in non-drastic temperature and pressure conditions even if the reaction kinetics are particularly slow. In this study, therefore, two different percentages of Pt (5 and 10 wt%) were added to a composite sample, containing 50 wt% of Mn oxide, through a ball milling technique in order to verify the reduction in absorption kinetics of the quantity of added catalyst. The effect of the catalyst quantity on the composite matrix was investigated through morphological analyses of the SEM-EDX and TEM types, with which it was found that the distribution of Pt is more homogeneous compared to the sample containing 5%. XRD studies confirmed the simultaneous presence of the amorphous structure of the polymer and the crystalline structure of Pt, and absorption tests with the Sievert method verified a better kinetic reaction of the 10% Pt sample. In parallel, a modeling study, using the ab initio Density Functional Theory (DFT), was performed. The supercell for this study was Mn₂₂Pt₂O₄₈. The number of H atoms gradually increased, starting from 2 (Mn₂₂Pt₂O₄₈H₂), where the initial desorption energy was 301 kJ/mol, to 211 kJ/mol for 12 H atoms (Mn₂₂Pt₂O₄₈H₁₂). From the experimental H₂ absorption value (0.22 wt%), the number of respective H atoms was calculated (n = 5), and the corresponding desorption energy was equal to about 273 kJ/mol. Full article