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In recent studies by Yalouz et al. [J. Chem. Phys. 157, 214112 (2022)] and Sekaran et al. [Phys. Rev. B 104, 035121 (2021) and Computation 10, 45 (2022)], density matrix embedding theory (DMET) has been reformulated through the use of the Householder transformation as a novel tool to embed a fragment within extended systems. The transformation was applied to a reference non-interacting one-electron reduced density matrix to construct fragments' bath orbitals, which are crucial for subsequent ground state calculations. In the present work, we expand upon these previous developments and extend the utilization of the Householder transformation to the description of multiple electronic states, including ground and excited states. Based on an ensemble noninteracting density matrix, we demonstrate the feasibility of achieving exact fragment embedding through successive Householder transformations, resulting in a larger set of bath orbitals. We analytically prove that the number of additional bath orbitals scales directly with the number of fractionally occupied natural orbitals in the reference ensemble density matrix. A connection with the regular DMET bath construction is also made. Then, we illustrate the use of this ensemble embedding tool in single-shot DMET calculations to describe both ground and first excited states in a Hubbard lattice model and an ab initio hydrogen system. Finally, we discuss avenues for enhancing ensemble embedding through self-consistency and explore potential future directions. [ABSTRACT FROM AUTHOR]

The effects of hydrogen absorption on the local lattice structure in palladium (Pd) were investigated by means of positron annihilation lifetime spectroscopy (PALS) and time-differential perturbed angular correlation (TDPAC) spectroscopy. The PALS measurements demonstrated that dislocations and vacancies formed in the preparation process of a pristine Pd plate can be clearly removed by vacuum annealing at 1073 K and the subsequent absorption of a large quantity of hydrogen, resulting in the production of the β-phase hydride PdH0.62, induces the formation of the open-volume defects again. It was also found that the absorbed hydrogen atoms remain in the Pd sample at 323 K but they are completely evacuated during 5 h heating at 383 K. In addition to the overall thermal behavior, an atomic scale observation of the hydrogen dynamics was carried out by means of TDPAC spectroscopy, indicating the nuclear quadrupole relaxation of the present (111m,111Pd → 111Ag→)111Cd probe, which evidently suggests that the hydrogen atoms show fast dynamic motion around the probe. From the temperature-dependent nuclear quadrupole relaxation rate, we obtained an activation energy of 41(4) meV for the motion. [ABSTRACT FROM AUTHOR]

A simple phenomenological thermodynamic model is developed to describe the chemical bonding and unbonding in homonuclear diatomic systems. This model describes the entire phase diagram of dimer-forming systems and shows a transition from monomers to dimers, with monomers favored at both very low and very high pressures, as well as at high temperatures. In the context of hydrogen, the former region corresponds to hydrogen present in most interstellar gas clouds, while the latter is associated with the long sought-after fluid metallic phase. The model predicts a molecular to atomic fluid transition in dense deuterium, which is in agreement with recently reported experimental measurements. [ABSTRACT FROM AUTHOR]

Transparent conducting oxides with p-type conductivity hold immense potential for various electronic applications. The role of native point defects in delafossite CuMO 2 (M = Al, Ga, In) as the source of p-type conductivity has been widely acknowledged. However, understanding the primary defects governing the electrical properties and devising strategies for improvement remains a critical challenge. In this study, we employ range-separated hybrid density functional calculations to elucidate the impact of acceptor defects and their interactions with hydrogen on electrical conductivity. Our findings demonstrate that hydrogen plays a pivotal role in controlling p-type conductivity in these oxides. Our investigation reveals that the interactions between hydrogen interstitial H i and copper vacancy V C u lead to the formation of stable complexes that are electrically inactive. Considerable binding energies are observed for H i – V C u complexes, indicating that they are highly bound complexes with low formation energy and, thus, high concentrations under both O-rich and O-poor conditions. A second hydrogen can be bound to V C u to form 2H i – V C u complexes, which are thermodynamically stable and function as a single donor. Furthermore, hydrogen can bind with the antisite acceptor defects, Cu M , forming H i – Cu M complexes. However, the lower binding energies associated with these complexes suggest likely dissociation into isolated H i and Cu M at relatively low temperatures. By shedding light on the strong influence of hydrogen passivation of acceptor defects, this study offers valuable insights into p-type conductivity in delafossite CuMO 2. [ABSTRACT FROM AUTHOR]

Resource partitioning is central to the incredible productivity of microbial communities, including gigatons in annual methane emissions through syntrophic interactions. Previous work revealed how a sulfate reducer (Desulfovibrio vulgaris, Dv) and a methanogen (Methanococcus maripaludis, Mm) underwent evolutionary diversification in a planktonic context, improving stability, cooperativity, and productivity within 300-1000 generations. Here, we show that mutations in just 15 Dv and 7 Mm genes within a minimal assemblage of this evolved community gave rise to co-existing ecotypes that were spatially enriched within a few days of culturing in a fluidized bed reactor. The spatially segregated communities partitioned resources in the simulated subsurface environment, with greater lactate utilization by attached Dv but partial utilization of resulting H2 by low affinity hydrogenases of Mm in the same phase. The unutilized H2 was scavenged by high affinity hydrogenases of planktonic Mm, producing copious amounts of methane. Our findings show how a few mutations can drive resource partitioning amongst niche-differentiated ecotypes, whose interplay synergistically improves productivity of the entire mutualistic community.

Understanding the structural behavior of solid hydrogen under high pressures is crucial for uncovering its unique properties and potential applications. In this study, starting from the phase I of solid hydrogen—free-rotator hcp structure, we conduct extensive ab initio molecular dynamics calculations to simulate the cooling, heating, and equilibrium processes within a pressure range of 80–260 GPa. Without relying on any structure previously predicted, we identify the high-pressure phase structures of solid hydrogen as P21/c for phase II, P6522 for phase III, and BG1BG2BG3 six-layer structure for phase IV, which are different from those proposed previously using the structure-search method. The reasonability of these structures are validated by Raman spectra and x-ray diffraction patterns by comparison with the experimental results. Our results actually show pronounced changes in the c/a ratio between phases I, III, and IV, which hold no brief for the experimental interpretation of an isostructural hcp transformations for phases I–III–IV. [ABSTRACT FROM AUTHOR]

Scandium nitride (ScN) is an attractive material for electronic applications due to its high n -type conductivity. Native defects and unintentional impurities may limit its electron concentration and reduce its mobility; therefore, it is important to control their formation and incorporation. Hydrogen and oxygen are unintentional impurities that are commonly present during growth and processing. They act as shallow donors in ScN and hence may be regarded as harmless or even favorable to achieving n -type conductivity. Here we show, using state-of-the-art first-principles calculations, that these impurities can be detrimental because they readily form complexes with scandium vacancies (V Sc ). Isolated V Sc have relatively high formation energies and thus have low concentrations and little impact on electronic properties. However, complexes between V Sc and either hydrogen or oxygen form more readily than the pristine vacancy and will act as both compensating and scattering centers. Our results point to the importance of controlling the incorporation of hydrogen and oxygen in ScN (and AlScN alloys) to avoid degradation of the electronic properties. [ABSTRACT FROM AUTHOR]

The nanocomposites of ferroferric oxide ([Fe.sub.3][O.sub.4]) with polyhydroxyurethane (PHU) were fabricated via a physical mixing approach. This process involved grafting poly(N-vinyl pyrrolidone) (PVPy) chains onto the surfaces of [Fe.sub.3][O.sub.4] nanoparticles via surface-initiated living radical polymerization. The PVPy-grafted [Fe.sub.3][O.sub.4] nanoparticles were directly incorporated into the precursors of PHUs [i.e., bis(cyclic carbonate) and a trifunctional amine] and the mixtures were cured at high temperatures to form organic-inorganic composites. This method ensured that [Fe.sub.3][O.sub.4] nanoparticles were finely dispersed within the PHU matrix through the strong intermolecular hydrogen bonding between PVPy and PHU. Compared to plain PHU network, the nanocomposites had enhanced thermomechanical properties, including higher glass transition temperatures ([T.sub.g]'s) and improved tensile mechanical properties. The inclusion of [Fe.sub.3][O.sub.4] nanoparticles also enhanced the shape memory properties of the PHU networks, improving shape recovery rates, fixity of transient shapes, and recovery of the original shapes. In addition, the nanocomposites demonstrated paramagnetic and photothermal properties and the photothermal behavior enabled a non-contact control of shape recovery. Highlights * Poly(N-vinyl pyrrolidone)-grafted [Fe.sub.3][O.sub.4] nanoparticles were synthesized. * Nanocomposites of PHU with [Fe.sub.3][O.sub.4] were prepared via a physical blending approach. * Incorporation of [Fe.sub.3][O.sub.4] resulted in improved thermomechanical properties. * The nanocomposites had the photothermal properties. KEYWORDS [Fe.sub.3][O.sub.4], nanocomposites, paramagnetic and photothermal properties, polyhydroxyurethane, shape memory properties, 1 | INTRODUCTION Polyurethanes (PUs) were first developed by Otto Bayer in 1939. (1) Over the past decades, PUs have been among the most major synthetic polymers. In general, the [...]

Localized atomic orbitals are the preferred basis set choice for large-scale explicit correlated calculations, and high-quality hierarchical correlation-consistent basis sets are a prerequisite for correlated methods to deliver numerically reliable results. At present, numeric atom-centered orbital (NAO) basis sets with valence correlation consistency (VCC), designated as NAO-VCC-nZ, are only available for light elements from hydrogen (H) to argon (Ar) [Zhang et al., New J. Phys. 15, 123033 (2013)]. In this work, we extend this series by developing NAO-VCC-nZ basis sets for krypton (Kr), a prototypical element in the fourth row of the periodic table. We demonstrate that NAO-VCC-nZ basis sets facilitate the convergence of electronic total-energy calculations using the Random Phase Approximation (RPA), which can be used together with a two-point extrapolation scheme to approach the complete basis set limit. Notably, the Basis Set Superposition Error (BSSE) associated with the newly generated NAO basis sets is minimal, making them suitable for applications where BSSE correction is either cumbersome or impractical to do. After confirming the reliability of NAO basis sets for Kr, we proceed to calculate the Helmholtz free energy for Kr crystal at the theoretical level of RPA plus renormalized single excitation correction. From this, we derive the pressure–volume (P–V) diagram, which shows excellent agreement with the latest experimental data. Our work demonstrates the capability of correlation-consistent NAO basis sets for heavy elements, paving the way toward numerically reliable correlated calculations for bulk materials. [ABSTRACT FROM AUTHOR]

SnO2 is a prototypical transparent conducting oxide that finds widespread applications as transparent electrodes, gas sensors, and transparent thin-film devices. Hydrogen impurities in SnO2 give rise to unintentional n-type behavior and unexpected changes to conductivity. Interstitial H (Hi) and H at an oxygen vacancy (HO) are both shallow donors in SnO2. An O–H vibrational line at 3155 cm−1, that can be produced by a thermal anneal at 500 °C followed by a rapid quench, has been assigned to the Hi center and is unstable at room temperature on a timescale of weeks. An IR absorption study of the decay kinetics of the 3155 cm−1 O–H line has been performed. The disappearance of Hi upon annealing has been found to follow second-order kinetics. Measurements of the decay rate for a range of temperatures have determined an activation energy for the diffusion of interstitial H in SnO2. These results provide fundamental information about how unintentional hydrogen impurities and their reactions can change the conductivity of SnO2 device materials in processes as simple as thermal annealing in an inert ambient. [ABSTRACT FROM AUTHOR]

SnO2 is a prototypical transparent conducting oxide that finds widespread applications as transparent electrodes, gas sensors, and transparent thin-film devices. Hydrogen impurities in SnO2 give rise to unintentional n-type behavior and unexpected changes to conductivity. Interstitial H (Hi) and H at an oxygen vacancy (HO) are both shallow donors in SnO2. An O–H vibrational line at 3155 cm−1, that can be produced by a thermal anneal at 500 °C followed by a rapid quench, has been assigned to the Hi center and is unstable at room temperature on a timescale of weeks. An IR absorption study of the decay kinetics of the 3155 cm−1 O–H line has been performed. The disappearance of Hi upon annealing has been found to follow second-order kinetics. Measurements of the decay rate for a range of temperatures have determined an activation energy for the diffusion of interstitial H in SnO2. These results provide fundamental information about how unintentional hydrogen impurities and their reactions can change the conductivity of SnO2 device materials in processes as simple as thermal annealing in an inert ambient. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) combustion and solid oxide fuel cells (SOFCs) can potentially reduce aviation-produced greenhouse gas emissions compared to kerosene propulsion. This paper outlines a methodology for evaluating performance and emission tradeoffs when retrofitting conventional kerosene-powered aircraft with lower-emissionH2 combustion and SOFC hybrid alternatives. The proposed framework presents a constant-range approach for designing liquid hydrogen fuel tanks, considering insulation, sizing, center of gravity, and power constraints. A lifecycle assessment evaluates greenhouse gas emissions and contrail formation effects for carbon footprint mitigation, while a cost analysis examines retrofit implementation consequences. A Cessna Citation 560XLS+ case study shows a 5% mass decrease for H2 combustion and a 0.4% mass decrease for the SOFC hybrid, at the tradeoff of removing three passengers. The lifecycle analysis of green hydrogen in aviation reveals a significant reduction in CO2 emissions for H2 combustion and SOFC systems, except for natural-gas-produced H2 combustion, when compared to Jet-A fuel. However, this environmental benefit is contrasted by an increase in fuel cost per passenger-km for green H2 combustion and a rise for natural-gas-produced H2 SOFC compared to kerosene. The results suggest that retrofitting aircraft with alternative fuels could lower carbon emissions, noting the economic and passenger capacity tradeoffs.

Green hydrogen, produced via water electrolysis using renewable electricity, will play a crucial role in decarbonizing industrial and heavy-duty transportation sectors. Anion exchange membrane water electrolyzers (AEMWEs) can overcome many of the performance and cost limitations of incumbent technologies, however, still suffer from durability challenges due to oxidative instability of anion-exchange ionomers. Herein, the use of an electro-active porous transport layer as anode (PTL-electrode) is demonstrated to enable efficient and durable AEMWEs. The stainless-steel PTL-electrodes are shown to have superior performance and durability compared to traditional catalyst layers containing ionomer and nanoparticle catalysts. An AEMWE cell operating at 2 A cm−2 for over 600 h exhibited a degradation rate of just 5 µV h−1. During operation, the surface composition of the stainless steel transforms into a mixture of iron and nickel oxyhydroxides, contributing to enhanced oxygen-evolution reaction activity. The combination of experimental work and modeling elucidates how the bulk structure of the PTL-electrode offers an additional design dimension to further improve electrolyzer performance. Lastly, a surface modification strategy is applied to a PTL-electrode to achieve an even higher performing AEMWE (2.3 vs 2.0 A cm−2 at 1.8 V). Overall, this work lays out pathways toward more efficient, durable, and affordable AEMWEs.

Elucidating the phase diagram of solid hydrogen is a key objective in condensed matter physics. Several decades ago, it was proposed that at low temperatures and high pressures, solid hydrogen would be a metal with a high superconducting transition temperature. This transition to a metallic state can happen through the closing of the energy gap in the molecular solid or through a transition to an atomic solid. Recent experiments have managed to reach pressures in the range of 400-500 GPa, providing valuable insights. There is strong evidence suggesting that metallization via either of these mechanisms occurs within this pressure range. Computational and experimental studies have identified multiple promising crystal phases, but the limited accuracy of calculations and the limited capabilities of experiments prevent us from determining unequivocally the observed phase or phases. Therefore, it is crucial to investigate the superconducting properties of all the candidate phases. Recently, we reported the superconducting properties of theC2/c-24,Cmca-12,Cmca-4 andI41/amd-2 phases, including anharmonic effects. Here, we report the effects of anisotropy on superconducting properties using Eliashberg theory. Then, we investigate the superconducting properties of deuterium and estimate the size of the isotope effect for each phase. We find that the isotope effect on superconductivity is diminished by anharmonicity in theC2/c-24 andCmca-12 phases and enlarged in theCmca-4 andI41/amd-2 phases. Our anharmonic calculations of theC2/c-24 phase of deuterium agree closely with the most recent experiment by Loubeyreet al(2022Phys. Rev. Lett.29035501), indicating that theC2/c-24 phase remains the leading candidate in this pressure range, and has a strong anharmonic character. These characteristics can serve to distinguish among crystal phases in experiment. Furthermore, expanding our understanding of superconductivity in pure hydrogen holds significance in the study of high-Tchydrides.

The over 15 million metric tonnes of carbon black produced annually emit carbon dioxide in the range of 29–79 million metric tonnes each year. With the renaissance of carbon black in many new renewable energy applications as well as the growing transportation sector, where carbon black is used as a rubber reinforcement agent in car tires, the carbon black market is expected to grow by 66% over the next 9 years. As such, it is important to better understand energy intensity and carbon dioxide emissions of carbon black production. In this work, the furnace black process is studied in detail using process models to provide insights into mass and energy balances, economics, and potential pathways for lowering the environmental impact of carbon black production. Current state-of-the-art carbon black facilities typically flare the tail gas of the carbon black reactor. While low in heating value, this tail gas contains considerable amounts of energy and flaring this tail gas leads to low overall efficiency (39.6%). The efficiency of the furnace black process can be improved if the tail gas is used to produce electricity. However, the high capital investment cost and increased operating costs make it difficult to operate electricity generation from the tail gas economically. Steam co-generation (together with electricity generation) on the other hand is shown to substantially improve energy efficiency as well as economics, provided that steam users are nearby. Steam co-generation can be achieved via back-pressure steam turbines so that the low-pressure exhaust steam (∼2 bar/120 °C) can be used locally for heating or drying purposes. Furthermore, the potential of utilizing hydrogen to reduce carbon dioxide emissions is investigated. Using hydrogen as fuel for the carbon black reactor instead of natural gas is shown to reduce the carbon dioxide footprint by 19%. However, current prices of hydrogen lead to a steep increase in the levelized cost of carbon black (47%).

BackgroundBiofilms in sulfide-rich springs present intricate microbial communities that play pivotal roles in biogeochemical cycling. We studied chemoautotrophically based biofilms that host diverse CPR bacteria and grow in sulfide-rich springs to investigate microbial controls on biogeochemical cycling.ResultsSulfide springs biofilms were investigated using bulk geochemical analysis, genome-resolved metagenomics, and scanning transmission X-ray microscopy (STXM) at room temperature and 87 K. Chemolithotrophic sulfur-oxidizing bacteria, including Thiothrix and Beggiatoa, dominate the biofilms, which also contain CPR Gracilibacteria, Absconditabacteria, Saccharibacteria, Peregrinibacteria, Berkelbacteria, Microgenomates, and Parcubacteria. STXM imaging revealed ultra-small cells near the surfaces of filamentous bacteria that may be CPR bacterial episymbionts. STXM and NEXAFS spectroscopy at carbon K and sulfur L2,3 edges show that filamentous bacteria contain protein-encapsulated spherical elemental sulfur granules, indicating that they are sulfur oxidizers, likely Thiothrix. Berkelbacteria and Moranbacteria in the same biofilm sample are predicted to have a novel electron bifurcating group 3b [NiFe]-hydrogenase, putatively a sulfhydrogenase, potentially linked to sulfur metabolism via redox cofactors. This complex could potentially contribute to symbioses, for example, with sulfur-oxidizing bacteria such as Thiothrix that is based on cryptic sulfur cycling. One Doudnabacteria genome encodes adjacent sulfur dioxygenase and rhodanese genes that may convert thiosulfate to sulfite. We find similar conserved genomic architecture associated with CPR bacteria from other sulfur-rich subsurface ecosystems.ConclusionsOur combined metagenomic, geochemical, spectromicroscopic, and structural bioinformatics analyses of biofilms growing in sulfide-rich springs revealed consortia that contain CPR bacteria and sulfur-oxidizing Proteobacteria, including Thiothrix, and bacteria from a new family within Beggiatoales. We infer roles for CPR bacteria in sulfur and hydrogen cycling. Video Abstract.

The operational cabin of hydrogen tube bundle containers (HTBCs) is susceptible to vibration and fatigue loads during transportation, which may result in hydrogen leakage and deflagration accidents. In this paper, a three-dimensional (3D) computational fluid dynamics (CFD) model is developed to simulate the effects of leakage diameter, leakage pressure, leakage direction and position on hydrogen leakage and diffusion in the operational cabin of HTBCs. The results demonstrate that the formation of vortex recirculation zones leads to the accumulation of flammable gas cloud (FGC) in the operational cabin. The medium leakage diameter (1.5 mm) and higher leakage pressure (20 MPa, 35 MPa) cause the operational cabin to be filled with FGC within 5 s, requiring the operational cabin to be designed with no possible ignition source inside. In addition, when hydrogen leaks from the +Z direction, the sensor responds within 0.31 s, which is 1.7 s earlier than the response time in the -Z direction, indicating that the existing sensor layout cannot meet the requirements of fast response. When the leak position (L 3) is close to the vent, the FGC volume proportion at 2 s is 19.3 % and 15.88 % lower than that of L 1 and L 2 , respectively, indicating that the leak position close to the vent can effectively slow down the accumulation of FGC. The research results have implications for the safety design of operational cabin of HTBCs, the layout of hydrogen sensors and vents, and the emergency response measures for hydrogen leakage. [Display omitted] • Numerical simulation reveals hydrogen leakage and diffusion behavior of tube bundle containers during transport. • Vortex recirculation zones cause flammable gas cloud accumulation in operational cabins. • Medium leakage (1.5 mm) and high pressure can fill the cabin with flammable gas cloud in 5 s. • Leakage direction and position affect hydrogen sensor response time. • The addition of hydrogen sensors and vents can reduce the risk of explosion. [ABSTRACT FROM AUTHOR]

ZnS is widely used in the photocatalytic decomposition of water to produce hydrogen due to its fast electron-hole pair generation and high negative potential. However, its absorption in the visible region is poor due to its wide band gap, and it has serious photogenerated carrier recombination problems. Herein, a shallow impurity energy level was introduced by doping the ZnS lattice with Cd. Due to its presence, electrons trying to return to the valence band are trapped and excited twice, suppressing the recombination of photogenerated carriers and greatly improving electron utilization. The Cd1.5-ZnS possesses a hydrogen production rate as high as 85722.20 μmol/g, which is 17 times higher than pure ZnS. Meanwhile, Cd1.5-ZnS has a narrower forbidden band and superior visible light absorption, and the serious photocorrosion problem of ZnS has been suppressed. This study provides a viable approach for the synthesis of photocatalysts with adjustable band gaps and enhanced hydrogen precipitation efficiency. The band gap of ZnS is narrowed by doping Cd2+ into the lattice structure of ZnS. Additionally, a shallow impurity energy level is created in close proximity to the bottom of the conduction band. This level has the capacity to trap electrons returning to the valence band from the conduction band and to excite them. thereby greatly increasing the utilization of electrons and reducing the formation of electron-hole complexes. Consequently, the Cd1.5-ZnS exhibits superior photocatalytic hydrogen production performance. [Display omitted] • Shallow impurity energy levels are introduced by Cd2+ doping to give the samples the ability to capture electrons secondarily. • The samples with the optimal Zn/Cd molar ratios exhibited photocatalytic hydrogen production rates up to 85722.20 μmol/g. • The issue of the wide bandgap of ZnS has been effectively improved. [ABSTRACT FROM AUTHOR]

This study concerns the development and experimental investigation of Direct Urea-Hydrogen Peroxide Fuel Cells (DUHPFC), with a particular emphasis on electrode preparation using nickel zinc iron oxide coated on stainless steel foil via the electrochemical deposition method, and the performance evaluation of single cells under varying operational conditions is also performed. This electrochemical deposition helps achieve a uniform and stable anode coating, which exhibits the high catalytic activity and stability, resulted in significantly enhanced urea oxidation reaction. The research further identifies an optimal performance for a single cell at 25 °C with 9 M KOH and 0.5 M urea, achieving a peak power density of 46.38 mW/cm2. The single cell demonstrates an open circuit voltage (OCV) of 0.72 V. Both energy and exergy efficiencies are further investigated for the cell performance and found to be 58% and 24%, respectively, at 5 M KOH. The electrochemical impedance spectroscopy (EIS) results reveal a significant reduction in impedance, from 30-Ωcm2 at 25 °C to 15-Ωcm2 at 65 °C, indicating an enhanced ionic conductivity and a reduced resistance. The present study results suggest that optimizing the electrode composition and operational parameters significantly improves the DUHPFC's performance, offering valuable insights for future fuel cell development. [Display omitted] • Urea and H₂O₂ enhance electrochemical reactions in DUHPFC systems. • Nickel zinc iron oxide catalyst boosts urea oxidation and cell efficiency. • Optimizing electrode composition and conditions improves DUHPFC performance. • Temperature and KOH concentration affect urea oxidation and cell efficiency. • Testing confirms the stability and durability of the developed anode. [ABSTRACT FROM AUTHOR]

The current energy and environmental problems demand the replacement of fossil fuels with renewable fuels. Research shows that hydrogen-enriched CNG fuels enhance the thermal efficiency of diesel engines while reducing gaseous emissions. This experimental work investigates the performance and emissions parameters of a diesel engine in dual fuel mode with hydrogen-enriched Bio-CNG (HBCNG). It is performed on a single-cylinder, four-stroke common rail direct injection (CRDI) diesel engine at 1500 rpm and 3.5 kW. The outcomes of this experiment are compared to a neat diesel operation. It is observed that at low load with 30% gaseous fuel substitution (GFS), brake thermal efficiency decreases by 13.70% and 15.53% for hydrogen and BCNG-enriched diesel, respectively. Similarly, at medium load, with the gaseous mixture of 40% H 2 and 60% BCNG co-combusted with 60% diesel, the BTE improves by 15.83%. At high load, 40% gaseous fuel mixture (40% H 2 + 60% BCNG) combustion with diesel results in 21.25% enhanced BTE. Moreover, at the same load condition and GFS, emissions of HC increase by 41.59%, CO decreases by 30%, CO 2 decreases by 55.36%, and NO x decreases by 25.94%. • The experiment is performed on a common rail direct injection diesel engine. • Hydrogen and Bio-CNG enriched diesel are used as the fuel. • Hydrogen and Bio-CNG mixture proportion in diesel are varied between 0 and 40%. • The engine load is varied between 0 and 80%. • The performance and emission parameters enhanced for 40% gaseous fuel mixture. [ABSTRACT FROM AUTHOR]

The present work is devoted to the synthesis of perovskite LaAlO 3 by Sol-Gel approach and its application for the photo-evolution of H 2 in conjunction with cobalt ferrite CoFe 2 O 4 prepared by nitrate route. The thermal analysis (TG/DSC) showed that the formation is completed at 600 °C. The X-ray diffraction (XRD) pattern is characteristic of a single phase, crystallizing in a rhombohedral symmetry with a crystallite size of 36 nm. The SEM micrographs revealed a homogeneous structure with an agglomeration of shaped grains (40–80 nm). The forbidden band (3.39 eV), calculated from diffuse reflectance data, is assigned to the ligand charge transfer O2−: 2p → Al3+: 3s orbital. As prepared, LaAlO 3 is an n -type semiconductor as demonstrated from the capacitance - potential (C−2 - E) graph with an electron density of 9.4 × 1014 cm−3 due to oxygen under-stoichiometry. Attention was directed to photo-electrochemistry in connection with water reduction into hydrogen. With a negative conduction band potential (−0.11 V SCE), H 2 generation can be synergized over the hetero-system by visible light. The photocatalytic capability of CoFe 2 O 4 25%/LaAlO 3 revealed a high H 2 generation of 963 μmol g−1 in the alkaline electrolyte (NaOH, 0.1 M) with a catalyst dose of 1 mg mL−1, which is 1.3 times more than CoFe 2 O 4 under similar conditions. Photoactivity is significantly improved by 60%, up to 2400 μmol g−1 in the presence of oxalate C 2 O 4 2− as a hole scavenger in the hetero-junction, two hydrogen release tests were successfully recorded. The higher H 2 production in the hetero-junction system is attributed to the lower recombination rate of electron/hole (e−/h+) in the material, due to the large band bending at the solid interfacial. [Display omitted] • The perovskite LaFeO 3 nanoparticle was prepared using a sol-gel method with nitrate precursors. • The heterogeneous nanocomposites CoFe 2 O 4 /LaAlO 3 were prepared using a simple mechanical method. • The conduction band (−0.11 V SCE) of LaAlO 3 suggests H 2 formation in the LaAlO 3 /CoFe 2 O 4 system. • The photocatalytic capability of CoFe 2 O 4 25%/LaAlO 3 75% showed high H 2 generation, reaching 963.10 μmol/g without a scavenger. • Photoactivity is significantly improved by 60%, reaching up to 2400 μmol/g in the presence of oxalate (C 2 O 4 2−) as a hole scavenger in the CoFe 2 O 4 25%/LaAlO 3 75% system. [ABSTRACT FROM AUTHOR]

Supercritical water (SCW) gasification technology can enable the efficient utilization of coal by converting it to hydrogen-rich gas. However, poly-cyclic aromatic hydrocarbons and heavy components, which are intermediates of supercritical water gasification, tend to generate char, hindering the complete gasification of coal. In this work, phenol is recycled to enhance the gasification process and reduce the formation of these intermediates during SCWG, and the regulation mechanism is investigated. The results demonstrate that both gas yield and gasification efficiency increase with the presence of phenol, reaching approximately 98.5% at 750 °C, concentration of 2%with the effect of phenol, which is 27% higher than that in the coal-water system. Organics removal rate reaches about 98% with the addition of phenol. Phenol can enhance the gasification performance by facilitating the conversion of heavy components to lightweight components. The transient reactivity of coal in the poly-condensation stage is increased by about 50 times with the presence of phenol. The regulation mechanism of phenol in the poly-condensation stage during coal gasification involves the decomposition of SCW forming hydroxyl radicals, which replaces the substituents on the benzene ring, facilitating the dissociation of benzene ring into small molecules that are prone to polymerize. The interacting force between phenol and multi-rings disrupts the conjugate structure, aiding in the decomposition of polycyclic organics into small molecules. • Investigated the regulating mechanism of phenol on the gasification process. • Hydrogen yield and gasification efficiency increases with the presence of phenol. • Nearly complete gasification (98.5%) is realized with the presence of phenol. • The organics removal rate reaches about 98% with the presence of phenol. • Reactivity of coal in the polycondensation stage increased by 50 times with phenol. [ABSTRACT FROM AUTHOR]

Studying the synergistic effects of dilution gases and hydrogen on the laminar combustion characteristics and NO X -emission concentrations of methane/air can contribute to achieving efficient and clean natural-gas combustion. This study quantitatively analyzes the impact of N 2 and CO 2 as dilution gases on the laminar combustion characteristics and NO X emissions of methane/air under different equivalence ratios. The virtual gases FN 2 and FCO 2 are introduced to distinguish between the physical and chemical effects of the dilution gases. Subsequently, the effect of hydrogen addition on the laminar combustion characteristics and NO X emissions of a methane/5% dilution gas/air mixture is investigated. Finally, the synergistic effects of the dilution gases and hydrogen on the laminar flame speed and NO X -emission concentrations of methane/air under various blending conditions are discussed. The results indicate that CO 2 exhibits a more substantial reduction in laminar flame speed, flame temperature, key radical concentrations, and NO X -emission concentrations than N 2 , primarily because of its physical effects. N 2 has minimal chemical effects, but marginally increases NO X emissions. The addition of hydrogen increases the laminar flame speed and key radical concentrations of the methane/dilution gas/air mixture. however, significant differences in the NO X -concentration trends with increasing hydrogen-blending ratios are observed for the three equivalence ratios (Φ = 0.7,1.0,1.4). Selecting appropriate blending ratios of dilution gases and hydrogen can simultaneously enhance the laminar flame speed of methane/air while reducing the NO X -emission concentrations. This study provides valuable insights into the optimization of the blending ratio of hydrogen-enriched natural-gas engines coupled with exhaust-gas recirculation. • Effects of N 2 and CO 2 on combustion characteristics of CH 4 /air are compared. • Physical and chemical effects of N 2 and CO 2 are distinguishedd. • Coupling H 2 with dilution gases enables clean and efficient combustion of CH 4. • Optimal blending ratios of dilution gases and hydrogen are discussed. [ABSTRACT FROM AUTHOR]

A new design of plasma-assisted injector to ignite or stabilize combustion is presented. This design is intended to produce discharges that penetrate the combustion chamber instead of staying at the wall. This plasma-assisted injector, simple and robust, allows compact designs for a weakly intrusive implementation in engines, and is compatible with either air or fuel, depending on the process or application. A prototype was manufactured, implemented and tested with quasi-DC discharges on the LAPCAT2 Dual Mode Ramjet combustor at LAERTE facility in ONERA. Combustion tests showed earlier ignition and increased pressure when the plasma was turned on with a measured plasma power of 1.4 kW. • Presentation of the design and principle of a new plasma assisted injector. • Demonstration of its ability to generate discharges penetrating the flow. • Characterization of the discharge dynamics and its interaction with the gas flow. • Comparison of the discharge behavior in hydrogen vs air. • Ability of the plasma assistance to enhance supersonic combustion. [ABSTRACT FROM AUTHOR]

Although two-stage anaerobic digestion (TSAD) is not a novel process, information of the process stability, microbial community and effective operating conditions is limited and often contradictory. In this work, the influence of different carrier materials (polyurethane foam, carbon felt, Raschig rings and a combination of carbon felt and Raschig rings) on the performance of the thermophilic TSAD of dairy wastewater was studied. The organic loading rate (OLR) in the acidogenic reactor (RH) was gradually increased from 13.74 to 32.56 g COD/(L d), and from 0.64 to 11.46 g COD/(L d) in the methanogenic reactors by correspondingly reducing the hydraulic retention time (HRT). The highest hydrogen production rate of 1280.3 mL/(L·d) and hydrogen yield of 93.2 mL/g COD were achieved at OLR of 13.74 g COD/(L·d), but hydrogen production stopped at higher OLR. The main soluble metabolites in RH were butyrate and lactate, and the microbial community was dominated by Streptococcus , Thermoanaerobacterium , Veillonellales-Selenomonadales and Pseudomonas. The highest methane production rate (2674 mL/(L·d) at HRT of 0.5 days) was observed in the reactor with polyurethane foam, while the highest methane yield (305.5 mL/g COD at HRT of 1.5 days) was obtained in a reactor containing carbon felt. Spirochaetaceae , Desulfomicrobium , Anaerolineaceae , Candidatus Caldatribacterium and Cloacimonadaceae W5 were linked to these materials and explained the highest methanogenic performance. [ABSTRACT FROM AUTHOR]

Fuel cell technology emerges as a promising green solution, offering mitigation to global warming, air pollution, and energy crises. This eco-friendly approach is witnessing a surge in adoption within the automotive sector, with fuel cell buses, cars, scooters, forklifts, and more, becoming increasingly prevalent. The automobile industry has been rapidly advancing fuel cell technology, inching closer to the commercialization of fuel cell vehicles. As various technical hurdles are surmounted and costs are reduced, fuel cell vehicles are poised to become a competitive force in the automobile market, presenting an excellent solution for environmental sustainability and energy efficiency. This review paper delves into the fundamentals of fuel cells, their characteristics, and their applications in the automotive realm, exploring their prospects in comparison to traditional technologies. Furthermore, it sheds light on the existing research and industrial developments in hydrogen and fuel cell technologies. Additionally, a comprehensive comparison is provided between various fuel cell cars that have already been commercialized, enabling readers to understand the current market landscape. The review also analyses the advantages and challenges associated with fuel cell technology, offering insights into its future development trajectory. Through this comprehensive exploration, readers can gain a deeper understanding of fuel cell technology and its potential in revolutionizing the automotive industry. [ABSTRACT FROM AUTHOR]

This study proposes a pathway to improve the efficiency of the hydrogen liquefaction process by including single-phase turboexpanders in the final hydrogen expansion. A sensitivity study compares three configurations. All three expansions have the same inlet and outlet pressures, while the inlet temperature is the same for Cases A and C but not for Case B. Case A is a standard isenthalpic expansion using a Joule-Thomson valve. Case B uses a fully wet turboexpander which expands on the liquid side of the two-phase curve and hence requires more cooling prior to the expansion. Case C is a compromise where the single-phase expansion is done by a turboexpander and the two-phase expansion by a Joule-Thomson valve. For the WE-NET configuration analysed (and a 50-bar top pressure), Case C has an increase in yield of 13.3% points and in exergetic efficiency of 4.6% points, compared to the baseline (Case A). • Proposal of new expansion configurations to increase hydrogen liquefaction efficiency. • Three final hydrogen expansion configurations are compared. • Single-phase turboexpander and Joule-Thomson valve in series beneficial. • This new configuration increases both yield and exergetic efficiency. [ABSTRACT FROM AUTHOR]

The implementation of hydrogen fuel cell vehicle (HFCV) policies represents a crucial strategy in addressing global warming within the transportation sector. This study assesses the impact of these policies on HFCV-related stock returns from 2019 to 2023, utilizing static and dynamic contagion tests to construct a contagion network. The results indicate several key findings: (1) both fuel cell (FC)- and hydrogen-oriented policies exhibit significant contagion effects across the HFCV supply chain, particularly between FC/hydrogen sectors and their upstream, midstream, and downstream counterparts, with stronger contagion pre-2021 and a modest decline post-2022; (2) in 2020, FC-oriented policies dominated contagion dynamics, with a notable shift towards hydrogen-oriented policies after 2021; (3) prior to 2021, contagion rates reached as high as 80%, largely driven by higher-order co-moments rather than linear correlations, but declined to below 25% after 2021; (4) upstream sectors within the HFCV supply chain are more sensitive to policy contagion compared to midstream and downstream sectors; and (5) among the 10 policies analyzed, the 2021–2023 New Energy Vehicle Industry Development Plan had the most substantial impact, both driving and receiving policy shocks within the HFCV network. These findings offer critical insights into the energy-economic interactions shaping the HFCV market, providing valuable guidance for policymakers and industry stakeholders aiming to promote sustainable transport strategies. • To study policy impact on HFCV industrial chain stock returns. • Use the contagion test to judge the impact of policy shocks on related sectors. • Upstream HFCV sectors are more receptive to policy contagion. • New Energy Vehicle Industry Development Plan wields the strongest influence. [ABSTRACT FROM AUTHOR]

In 2 O 3 @ZnO nanotubes were fabricated using MIL-68@ZIF-8 as a template, and then fern-like In 2 O 3 @ZnO@Pd nanotubes with unique structures were synthesized by chemical reduction. The samples were thoroughly investigated to study their composition, morphology and structure. Hydrogen (H 2) sensitization characteristics of sensor of In 2 O 3 @ZnO@Pd nanotubes with different ZnO and Pd contents were tested at room temperature (RT). The In 2 O 3 @ZnO@Pd nanotube sensor with a palladium（Pd）content of 2.0 wt% exhibits a high response (R a /R g = 270) and fast response time (t res = 32 s) and recovery time (t rec = 116 s) to 10,000 ppm H 2 at RT, as well as excellent selectivity, behaving a response nearly six times that of interfering gases. The excellent hydrogen sensing performance indicates that the fern-like In 2 O 3 @ZnO@Pd nanocomposite has good application prospects and is an excellent hydrogen-sensitive material. In this paper, In 2 O 3 @ZnO nanotubes were prepared using nanoscale MIL-68@ZIF-8 as a template to enable further optimization of morphology with smaller scales. Fern-like In 2 O 3 @ZnO@Pd nanotubes with unique structures were then synthesized by doping noble metal Pd and chemical reduction. The H 2 sensing properties of fern-like In 2 O 3 @ZnO@Pd nanotubes to different concentrations of hydrogen were investigated by varying the contents of zinc oxide (ZnO) and Pd elements. The In3Zn–Pd 2 sample showed excellent sensitivity and selectivity to 10,000 ppm H 2 with a maximum response of 277.1 at RT, which was 6.6 times higher than pure In 2 O 3 @ZnO at the same temperature, and the response value was nearly six times that of the interfering gas. Moreover, the response/recovery time of the NT-Pd 2 samples was 32 and 116 s, respectively, which was substantially shorter than those of In 2 O 3 @ZnO at the same temperature (183 and 355s). [Display omitted] • Hydrogen gas sensor fabricated using fern-like In 2 O 3 @ZnO@Pd nanotubes. • The sensor detects hydrogen at room temperature providing a wider and safer range of applications. • The sensor has a high response value (277.1) and short response/recovery time (32s/116s) to hydrogen at room temperature. • The sensor has good selectivity and a response value of up to six times that of interfering gases. [ABSTRACT FROM AUTHOR]

This work assesses a chemical plant for the conversion of biogas into negative emission "emerald hydrogen" via electrified reforming and CO 2 separation. Electrification of the reformer allows for enhanced syngas production, compact reactor designs and flexible operation, thanks to the avoidance of combustion and heat transfer through pressure walls. The integration of the process with solar and wind power generation has been assessed by part-load process simulations and plant sizing and operation optimization through yearly simulations with hourly discretization. Different European locations with different wind and solar availabilities were assessed considering (i) short- and long-term cost scenarios for renewables and battery technologies and (ii) different plant size (from 390 to 3900 Nm3/h of biogas capacity). The overarching scope of the paper is to calculate the cost of the produced hydrogen and the economic value of flexibility for plants installed in different locations, under different cost scenarios. At design load, the assessed process consumes 17.7 kWh of electricity per kg H2 and retains 96% of the biogas chemical energy in the produced hydrogen. Additionally, 76% of the biogenic carbon is recovered as high-purity liquid CO 2 , achieving up to −9 kg CO2 /kg H2 negative emissions. When powered with 95% of renewable energy, hydrogen production cost ranges from 2.5 to 2.9 €/kg for a long-term REN cost scenario and large-scale flexible plant to 5.9–7.1 €/kg for a short-term REN cost scenario and small-scale inflexible plants. For small-scale plants, flexibility allows to reduce the hydrogen production cost by 11–16% with respect to the inflexible plant in the short-term renewables cost scenario and by 1–4% in the long-term cost scenario. For large-scale plants, the adoption of a flexible plant leads to a reduction of 17–23% of the hydrogen cost in the short-term scenario and of 6–22% in the long-term scenario. Operational flexibility of electrified reforming allows reducing the cost of negative-emission bio-hydrogen by 1–23%, depending on location and cost scenario. [Display omitted] • Process engineering study with off-design model. • Economic optimization of flexible process with PV, wind, BESS and gas storages. • 17.7 kWh/kg H2 of electric consumption and up to −9 kg CO2 /kg H2 negative emissions. • H 2 cost of 2.5–6.2 €/kg depending on location, REN cost scenario and plant capacity. • Flexibility reduces H 2 cost by 1–23% depending on location and REN cost scenario. [ABSTRACT FROM AUTHOR]

Diesel reforming is a promising hydrogen production technology used for the clean energy conversion of high-carbon-content fuels. Although the reaction system has been established, predicting the optimal reaction conditions for the system remains challenging. Here, we obtained a set of 675 data points from Aspen Plus simulations and trained regression models to predict the reaction condition ranges that yield the highest hydrogen production in diesel reforming. The ETR model achieved the best predictive performance, with an R2 value of 0.99. Interpretable machine learning methods revealed that temperature is a crucial feature determining the baseline hydrogen yield of the diesel reforming reaction, while the steam-to-carbon ratio is key to enhancing hydrogen yield. Our exploratory study underscores the ability of data-driven ML models to uncover the condition-yield relationship in catalytic diesel reforming for hydrogen production by isolating the effects of individual design parameters, a feat that is difficult to achieve through experimental means. [Display omitted] • Research methods combining Aspen Plus simulation and machine learning. • Interpretable machine learning models with deep analytical capabilities. • Obtain guidance intervals for reaction conditions that can be directly used. • Machine learning with minimal prediction and experimental errors. [ABSTRACT FROM AUTHOR]

This study explores the potential of hydrogen gas turbine engines for sustainable aviation, with a particular focus on their development for low subsonic to transonic flight regimes. Hydrogen offers notable advantages, including zero CO 2 emissions and high energy density. However, its widespread adoption is prevented by significant challenges in production, infrastructure, storage, aircraft design, and combustion technology. The limited availability of green hydrogen – the global production totaled only 127 kt in 2023, with 76% produced in China - raises concerns about the feasibility of a rapid shift to hydrogen-powered general aviation. Despite numerous pledges for hydrogen adoption in the Western world, major aircraft manufacturers have primarily engaged in marketing activities rather than substantial product innovation. To date, the only hydrogen aircraft demonstrator from this century is the 2012 Boeing Phantom Eye, which utilized modified hydrogen internal combustion engines rather than a gas turbine engine. The only hydrogen aircraft demonstrator with a gas turbine engine was the 1988 hybrid Tupolev Tu-155 which coupled one hydrogen gas turbine engine to other two jet fuel engines. This paper evaluates the current state of hydrogen gas turbine technology, comparing its combustion characteristics with traditional jet fuels and examining various NOx emission control techniques. It also investigates the potential of micro-mix lean combustion and staged combustion to achieve efficient and low-emission hydrogen combustion in gas turbines. Given the more extensive experience with terrestrial gas turbines compared to their aeronautical counterparts, the review includes insights from terrestrial power generation applications. Additionally, it considers hythane - a blend of hydrogen and natural gas - as a transitional solution for significantly reducing CO 2 emissions while progressing towards net-zero targets. The review underscores the urgent need for advancements in green hydrogen production, technology, and infrastructure to overcome existing barriers and enable a more sustainable aviation future powered by hydrogen. Importantly, the review emphasizes the need to move beyond mere virtue signaling and make tangible progress toward a hydrogen economy. [ABSTRACT FROM AUTHOR]

Even for short space flights, such as manned flights to the Moon back in the 60s, it became extremely obvious that electric batteries are completely unsuitable because of their huge mass needed to store the required supply of onboard energy. Therefore, already in the 60s of the last century, the USA and the USSR took the path of using a hydrogen storage system using hydrogen fuel cells. Solar-hydrogen energy systems for spacecraft reliably provide energy for carrying out various kinds of unscheduled work on board and for eliminating emergency situations. Surplus energy is constantly accumulated on board in the form of the chemical energy of cryogenic hydrogen. The article presents too the result of the development of a solar-hydrogen power supply system for spacecraft, the onboard network of which provides slow and fast processes. This paper delves into designing digital control systems for power conditioning devices on the example of charging-discharging device based on a boost DC-DC converter. The device was implemented to condition a storage battery by properly charging and discharging it. A technique for constructing a small signal model of the converter has been developed. This involves constructing a block diagram using the discontinuous switching functions and analog models of electrical circuit components. The transfer functions of the analog controllers for the two-loop subordinate control system were derived. Then the procedure of a bilinear z-transform to the given transfer functions was applied. As a result, the discrete transfer functions of the digital controllers were obtained. Realization both analog and digital controllers in Matlab Simulink confirmed their identical behavior and stability within the power converter. Experimental studies of the static and dynamic waveforms of the digital control system showed controllability and stability of the charging-discharging device for the storage battery in typical operating modes. Thus, the method of synthesizing digital control systems for energy converters is proved valid and applicable for designing new power conditioning devices within modern power supplies. [ABSTRACT FROM AUTHOR]

Transition metal compounds (TMCs) are potentially fruitful substitutes for noble metals for electrocatalytic splitting of water due to their intrinsic electrocatalytic activity, modifiable morphology, tunable electronic structure and their earth‐abundance. The combination of TMCs with graphene improves the dispersion of loaded catalysts, providing more catalytic active sites, enhancing the conductivity of hybrids, affording accelerated charge‐transfer kinetics, and minimizing catalyst bleaching, aggregation, and sintering under harsh reaction conditions. Additionally, graphene incorporation into TMCs modulates the electronic structure of active centers because of the synergistic interaction between them, thereby improving their catalytic performance. This review paper focuses on the recent progress made in designing different graphene‐transition metal‐based materials that can be used in the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and overall water splitting (OWS). In‐situ characterization methodologies and DFT calculations that facilitate catalyst development are discussed elaborately. Finally, the advancements made in the development of graphene‐supported transition metal compounds for use in a functional water electrolyzer have been explored. In conclusion, a few specific recommendations have been made about the current challenges related to the widespread production of effective HER/OER electrocatalysts for water electrolysis. [ABSTRACT FROM AUTHOR]

Reducing the cost of PEM water electrolyzers is crucial for making green hydrogen economically viable achievable by cheaper catalysts as well as bipolar plates. This study demonstrates for the first time the use of uncoated carbon bipolar plates (C‐BPs) as an alternative to titanium bipolar plates (Ti‐BPs). The corrosion phenomena of C‐BPs versus Ti‐BPs are investigated through ex situ and in situ accelerated stress tests. The findings show that pH values, especially between 1 and 0, exponentially influence the corrosion current density of bipolar plates. Ex situ tests revealed significantly higher corrosion current densities for C‐BPs compared to Ti‐BPs (e.g., 170 times higher at pH 1 and 80 °C). Yet, tests applying C‐BPs in a Proton Exchange Membrane Electrolyzer operated for at least 567 h at alternating current densities of 1 and 3 A cm⁻2 with low degradation rates (16.41 µV h⁻¹ at 1 A cm⁻2 and 31.92 µV h⁻¹ at 3 A cm⁻2), comparable to Ti‐BPs. Contrary to general perceptions, C‐BPs are stable under application‐ready conditions and do not corrode as previously expected. This study highlights the potential of C‐BPs in electrolyzers, showcasing the potential to reduce the costs of the electrolyzers. [ABSTRACT FROM AUTHOR]

The increasing demand for green hydrogen is driving the development of efficient and durable electrocatalysts for the hydrogen evolution reaction (HER). Nickel‐molybdenum (NiMo) alloys are among the best HER electrocatalysts in alkaline electrolytes, and here we report a scalable solution precursor plasma spraying (SPPS) process to produce the highly active Ni4Mo electrocatalysts directly onto metallic substrates. The NiMo coating coated onto inexpensive Ni mesh revealed an excellent HER performance with an overpotential of only 26 mV at −10 mA cm−2 with a Tafel slope of 55 mV dec−1. Excellent operational stability with minimum changes in overpotential were also observed even after extensive 60 hour high‐current stability test. In addition, we investigate the influence of different substrates over the catalytic performance and operational stability. We also proposed that a slow, but consistent, dissolution of Mo is the primary degradation mechanism of NiMo‐based coatings. This unique SPPS approach enables the scalable production of exceptional NiMo electrocatalysts with remarkable activity and durability, positioning them as ideal cathode materials for practical applications in alkaline water electrolysers. [ABSTRACT FROM AUTHOR]

Cobalt (Co) is widely used in Fischer–Tropsch synthesis (FTS), converting synthesis gas, carbon monoxide + hydrogen (CO + H2), to long-chain hydrocarbons. The adsorption of CO on the Co surface is the key step in FTS. In this work, the effect of CO adsorption sites on the reactions between CO and H2 was investigated by using density functional theory (DFT). The energetics and structures of the reactions between the adsorbed CO (CO*) and H2/adsorbed H2 (H2*)/adsorbed H atom (H*) were calculated. The results show that the reaction between CO* and H2 is initiated by the molecular adsorption of H2 on the Co surface. The reactions between CO* and H2*/H* are influenced by CO adsorption sites. For the reaction system of CO* + H2*, it has the lowest reaction barrier when CO is adsorbed at the hcp site, while for CO* + H*, it has the lowest reaction barrier when CO is adsorbed on the top site. Kinetic analysis indicates that to improve the reactivity of CO + H2 in FTS, the adsorption of CO should be controlled to favour the top and bridge sites. This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'. [ABSTRACT FROM AUTHOR]

The commercialization of the photocatalysis technology requires that the synthesis of the photocatalytic material is easy to scale up. Thus, the synthesis from earth‐abundant minerals represents one plausible solution to obtain materials by a scalable process with a lower environmental impact. So far, the most promising photocatalyst for this application is titanium dioxide (TiO2), which can be obtained from ilmenite ore; however, its synthesis usually implies toxic solvents and complicated reaction conditions. Thus, here is proposed an optimized method to extract higher amounts of TiO2 by a multivariable Plackett‐Burman design of experiments considering the mass of the ore precursor, the addition of phosphoric acid (H3PO4), the digestion temperature, the amount of base to adjust the pH, and the final thermal treatment. From this design, it was possible to minimize the heat treatment and the amount of base used to favor higher TiO2 (rutile) content with the presence of additional phases of iron oxides (Fe2O3) that act as co‐catalyst to enhance the photocatalytic activity. The photocatalytic activity of the TiO2/Fe2O3 composites obtained was investigated in four model reactions to obtain solar fuels (H2 evolution and CO2 reduction) and to remove endocrine water pollutants (bisphenol A and dyeing water), using visible and natural solar irradiation, respectively. [ABSTRACT FROM AUTHOR]

This study evaluates the potential of several biomasses differing in nature and composition for their valorization by pyrolysis and in line oxidative steam reforming. The first task involved the fast pyrolysis of the biomasses in a conical spouted bed reactor (CSBR) at 500 °C, in which product yields were analyzed in detail. Then, the oxidative steam reforming (OSR) of pyrolysis volatiles (gases and bio‐oil) was approached in a fluidized bed reactor (FBR). The reforming experiments were performed at 600 °C, with a steam/biomass (S/B) ratio of 3 and catalyst (Ni/Al2O3) space times of 7.5 and 20 gcat min gvol−1. Concerning equivalence ratio (ER), a value of 0.12 was selected to ensure autothermal operation. Remarkable differences were observed in H2 production depending on the type of biomass. Thus, pine wood led to a H2 production of 9.3 wt %. The lower productions obtained with rice husk (7.7 wt %) and orange peel (5.5 wt %) are associated with their higher ash and fixed carbon content, respectively, which limit the efficiency of biomass conversion to bio‐oil. However, in the case of the microalgae, the poor performance observed is because of the lower conversion in the reforming step toward gases due to the composition of its pyrolysis volatile stream. [ABSTRACT FROM AUTHOR]

Inspired by the direct charge transfer in the natural photosystems, herein, we design covalent triazine frameworks (CTFs) with direct electron transfer by constructing the minimal amount of –donor–acceptor 1–acceptor 2– type moieties in the CTF backbone for photocatalytic hydrogen evolution. By introducing only 0.75% of the acceptor 2, the as-prepared CTF exhibited an enhanced hydrogen evolution rate of 3215 μmol g−1 h−1. [ABSTRACT FROM AUTHOR]

Hydrogen production by methane catalytic decomposition is a promising method that also allows the formation of valuable carbon nanomaterials which can be utilized in transportation fuels, chemical synthesis, and fuel cell technology. In this study, bimetallic 3d transition metal (Ni, Fe, Co) catalysts supported on spherical mesoporous nanofibrous silica (KCC1) were successfully synthesized using a hydrothermal method followed by sono co-impregnation. The catalysts were evaluated for their performance in the catalytic decomposition of methane. Comprehensive characterization of the catalysts was conducted utilizing XRD, FTIR, SEM, TEM, STEM, XPS, H 2 -TPR, and BET techniques. XRD and TEM analyses confirmed the formation of Ni–Fe, Ni–Co, and Co–Fe bimetallic alloys on the nanofibrous silica without compromising its dendrimeric hierarchical structure. STEM HAADF imaging revealed a uniform dispersion of bimetallic nanoparticles within the spherical fibrous framework. Catalytic tests demonstrated that all bimetallic catalysts showed high stability and activity for methane cracking at 700 °C over 180 min of time on stream (TOS). Among them, Fe-based catalysts Ni–Fe/KCC1 and Co–Fe/KCC1 achieved the highest hydrogen yields of 80% and 60%, respectively. Methane conversion was 1.56 and 2.23 times higher in Ni–Fe/KCC1 compared to Co–Fe/KCC1 and Ni–Co/KCC1, respectively. Post-reaction characterization of the spent catalysts was performed using XRD, Raman spectroscopy, SEM, TEM, and TGA. XRD and Raman spectroscopy were used to evaluate the degree of graphitization and crystallinity in the carbon nanotubes (CNTs) produced on the catalysts, enabling a correlation with the catalyst properties. TEM examination was used to investigate the structural morphology and growth methods of the CNTs, including tip or base growth and chain-like or parallel-wall types. TGA results revealed that all bimetallic catalysts exhibited no amorphous carbon during methane cracking reaction. [Display omitted] • KCC1 framework enhances active site exposure and reactant/product diffusion. • Hierarchical dendritic layers pose a steric barrier, functioning as sintering-resistant support. • Highly dispersed bimetals obtained over KCC1 due to large accessible surface area. • KCC1 supported bimetallic (Ni, Fe, Co) alloys synergistically contributes to high stability. • Ni–Fe/KCC1 exhibited high catalytic activity with graphitized carbon structures. [ABSTRACT FROM AUTHOR]

Geochemical investigation of hydrogen (H 2), brine, rock formations, and residual gases (nitrogen – N 2 , methane – CH 4 , and carbon dioxide – CO 2) is crucial for understanding H 2 storage processes in depleted gas reservoirs. This study examines the effects of injecting a gas mixture (60% H 2 + 30% N 2 + 5% CH 4 + 5% CO 2) into Bandera Grey sandstone with notable clay mineral content. The experiment lasted 50 days at 42 °C, 1350 psi, and 5 wt% NaCl brine, with detailed analytical characterization before and after aging. Results show minimal sample reactivity, causing slight alterations in petrophysical characteristics. Dissolution primarily affected dolomite and barite minerals, while illite and kaolinite caused pore blockage. Gas chromatography data indicate only 0.45% of injected H 2 is lost (via dissolution in brine and reaction with CO 2), CH 4 increased by 6.22%, N 2 remained stable, and CO 2 decreased by 1%. These results provide valuable insights into the feasibility and safety of utilizing depleted gas reservoirs for H 2 storage. • Effect of storing 60% H 2 and 40% cushion gas in clay-rich sandstone is investigated. • Geochemical reactions (dissolution/precipitation) induced by the mixture are very weak. • PH increased from 6.13 to 7.24 led to mineral dissolution and precipitation. • Only 0.45% of injected H 2 was lost based on gas chromatography. • Findings provide insights into the feasibility and safety of depleted gas reservoirs for H 2 storage. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigated the thermal performance of a low-pressure cryogenic vaporizer for liquified hydrogen supply system. A performance analysis model was developed by the modified effectiveness-NTU method considering the axial conduction and phase change of liquified hydrogen. In the analysis model, a plate-fin heat exchanger (PFHE) was chosen as the type of a cryogenic vaporizer. The inlet temperature and pressure conditions of liquified hydrogen were 20 K and 10 bar, respectively and the outlet temperature condition of hydrogen was a room temperature. Based on the theoretical results, we presented effects of geometric parameters on the performance of the vaporizer under the fixed pumping power condition. Especially, it is shown that the effectiveness of the hot fluid and cold fluid exhibit opposite trends depending on the axial conduction. In addition, we presented the effect of the aspect ratio of microchannels on the effectiveness considering both cases where the microchannel heights of the EGW mixture and hydrogen were either the same or different. Also, we showed the effect of the vaporizer length on the performance of the vaporizer. Finally, geometric parameters that can satisfy the two target performances are suggested. • Thermal performance of a low-pressure cryogenic vaporizer for liquified hydrogen was investigated. • Modified effectiveness-NTU method considering the axial conduction and phase change of liquified hydrogen were used. • Effectiveness of the hot fluid and cold fluid exhibit opposite trends depending on the axial conduction. • Effects of the aspect ratio of microchannels and the length on the effectiveness were presented. [ABSTRACT FROM AUTHOR]

Methanol is recognized as source of hydrogen production, making it a suitable fuel for sustainable development. However, hydrogen production methods remain a concern. An experimental setup and a simulation model in Aspen Plus, incorporating an evaporator and cracker, are developed for hydrogen production. The effects of dimensional parameters, including the length and diameter of the cracker, temperature, and pressure in the presence of the catalyst SCST- 403, on hydrogen production and methanol conversion via thermal catalytic cracking have not been discussed yet . The experimental results show that the optimum hydrogen mole fraction exceeds 0.52, and methanol conversion exceeds 60% at a length of 2.83 m, diameter of 4.07 mm, temperature of 500 °C, and pressure of 2.7 MPa. The investigation is extended to redesign the cracker unit using Aspen Plus based on reaction kinetics. Simulations on various dimensions, temperatures, and pressures reveal that, after redesigning, the optimum hydrogen mole fraction exceeds 0.60, and methanol conversion reaches 85% at a length of 4.5 m, diameter of 5.2 mm, temperature of 500 °C, and pressure of 3 MPa. [Display omitted] • Design a compact-size methanol cracking unit for hydrogen production. • Utilize high temperature conditions for faster methanol catalytic cracking. • On-board syn-gas production, primarily hydrogen, by methanol decomposition. • Design variations aim to enhance methanol cracking and hydrogen production efficiency. [ABSTRACT FROM AUTHOR]

Conventional fossil fuel-powered vehicles are gradually being replaced by electric and hydrogen vehicles in the transportation sector. Even with all the recognized benefits and recent advancements in energy efficiency, decrease of noise, and environmental impact reduction, the market of electric and hydrogen mobility is still not up to par. Allocating charging stations in metropolitan areas for electric vehicles is considered as one of the most significant obstacles preventing electric and hydrogen vehicles from becoming more widely used. In this paper, an efficient approach aimed at finding optimal locations for electric vehicles (EV) charging stations in urban areas is proposed. Particle Swarm Optimization algorithm technique is utilized with the proposed approach. Various parameters were taken into consideration in this work, such as the horizontal distance that EVs travel to reach charging stations (CSs), and positive slope that EVs face to reach charging stations. The optimization problem is formulated as a Mixed-integer problem. The objective function works on minimizing the energy consumption of EVs to reach CSs in the investigated area. Difference constraints are incorporated with the proposed approach in order to increase the accuracy and efficiency of the proposed approach. The proposed approach is applied on real world datasets and is experimentally validated using through comparison with Genetic Algorithm and the greedy approach. The results demonstrate that the proposed approach saves energy about 22% and 43% compared to the genetic algorithm and greedy technique, respectively. [ABSTRACT FROM AUTHOR]

In the pursuit of more sustainable steelmaking, stakeholders are engaging in a transformative exploration of hydrogen-based direct reduction as an alternative to conventional blast furnaces. As a bridging step between single iron ore pellets and industrial shaft furnaces, direct reduction modeling in a fixed bed configuration can play a central role for subsequent process optimization. However, this task involves numerous challenging steps: generation of a realistic packed bed structure along with a good quality mesh and, foremost, reliable transport and kinetic processes for the individual pellets. Therefore, the present work formulates a sound methodology to progress from single particle considerations to 3D-CFD simulations of iron ore reduction using hydrogen in fixed beds, further supported by validations regarding the bed structure and the overall reduction against experimental data from the literature of a 500 g iron ore bed. The current results offer new insights into the direct reduction process, revealing, for instance, the non-uniform reduction of pellets within the bed, the presence of gas pockets, or the importance of the temperature deviation due to the endothermic reduction of iron oxides with hydrogen. • Simulation of hydrogen-based direct reduction fixed bed using particle-resolved CFD. • Three-step methodology: single pellet – bed construction with discrete element method – reactive CFD. • Comprehensive validation with experimental data, including a 500 g iron ore bed. • Detailed insights reveal non-uniform reduction and gas pocket formation. • High water presence and significance of temperature deviations highlighted. [ABSTRACT FROM AUTHOR]