Search Results (2,418)

Demand for greener and safer chemistries has driven the innovation of bioinspired and enzyme-mimicking catalysts for selective and efficient oxidation and hydrogenation under mild conditions. Natural catalysts, including peroxidases, oxidases, hydrogenases, oxygenases and dehydrogenases, boast remarkable activity, specificity, stability, selectivity, low energy requirements and atom economy. Disadvantages of enzymes, such as poor thermal stability, a narrow operational range, low recovery yield and the expense of purification, are motivating the discovery and design of enzyme substitutes. Several artificial platforms have appeared recently: nanozymes, artificial metalloenzymes, biomimetic metal Complexes, MOFs, atomic catalysts, bioinorganic hybrid systems, among others. These systems aim to replicate key structural and mechanistic features of enzymes while providing greater operational stability, recyclability, and scalability. Recent work has demonstrated the benefit of enzyme mimics in increasing eco-sustainability in reactions such as alcohol oxidation, selective alkane oxidation, waste degradation, catalytic photooxygen activation and biomass waste conversion. Similarly, biomimetic hydrogenation catalysts have shown outstanding activity in asymmetrically hydrogenating chemicals, reducing CO₂ into chemicals, hydrogenation by hydrogen transfer and creating hydrogen through water. Through control of active sites, second coordination sites, defects and electrons/protons in the system, significant gains have been seen in reaction selectivity and frequency of turning over substrate into product. Nanozymes, biohybrid catalysis and artificial catalysts guided by deep learning are further broadening the applications of biomimetic catalysis in oxidation and hydrogenation. The article review aims to provide a summary of the most current progress with bioinspired and enzyme-mimicking catalysts, focusing on catalytic mechanisms, how to design such catalysts, how green chemistry benefits from their development and where further application is likely in the coming years. Full article

The safety and stability of onboard Liquid Hydrogen (LH₂) storage systems depend strongly on gas–liquid two-phase flow, heat transfer, and phase change under sloshing; however, the coupled influence of filling ratio and sloshing on thermo-hydrodynamic behavior remains underexplored. We develop a Volume of Fluid (VOF)-based two-phase Computational Fluid Dynamics (CFD) model in ANSYS Fluent to quantify interfacial dynamics, pressure response, and temperature-field evolution in LH₂ tanks subjected to sinusoidal acceleration for filling ratios from 10% to 90%. Increasing the filling ratio strengthens net condensation in the ullage and thus intensifies depressurization. As the filling ratio increases from 10% to 90%, the pressure reduction over the 2.0 s sloshing process increases from 0.418 kPa to 2.410 kPa, and the corresponding initial depressurization rate rises from 0.209 to 1.205 kPa s⁻¹. Free-surface motion decreases with filling ratio: at 10%, large interface excursions can induce gas-cavity formation and splashing, increasing the risk of intermittent propellant supply, whereas at 90% the interface is constrained and oscillations are suppressed. Higher filling ratios lead to faster ullage cooling and larger temperature oscillations. The liquid warms modestly, and its warming rate decreases nonlinearly with filling ratio, consistent with the larger effective thermal mass at higher fillings. Overall, the obtained mechanistic understanding can support the engineering design of onboard LH₂ tanks, including filling-ratio selection and thermal-management optimization under sloshing conditions. Full article

Synergistically optimizing electronic structure and exposing abundant active sites is a promising route to enhance electrocatalytic activity, yet remains challenging. Herein, a hierarchical tubular structure of vanadium-incorporated molybdenum phosphide (V-MoP) was successfully constructed for highly effectively alkaline hydrogen evolution. Molecular self-assembly of a V-substituted Keggin-type polyoxometalate (POM) with a simple organic ligand was exploited to induce a hollow tubular precursor and trigger precise V doping by virtue of the intrinsic structural features of POMs, thereby realizing simultaneous morphology engineering and electronic structure modulation. The unique open-ended hollow tubular structure, which furnishes both internal and external surfaces and superhydrophilicity, increases the exposure of electrochemical active sites, promotes rapid electrolyte penetration and shortens mass transfer pathways. Moreover, V doping effectively modulates the electronic structure of MoP, further renders Mo and P sites more electron-rich, meanwhile triggering the coexistence of V³⁺ and V⁵⁺, which further promotes water dissociation and hydrogen evolution. Consequently, the V-MoP catalyst exhibits significantly enhanced activity, far beyond that of pristine bulk MoP and bulk V-MoP, and even surpasses that of commercial 20% Pt/C at high current densities. This work provides a feasible strategy for designing advanced electrocatalysts with tailored morphology and tunable electronic structures. Full article

The conversion of bio-waste into functional energy materials provides a robust platform for addressing both environmental and energy challenges. In this paper, discarded absorbent pads are transformed into carbon-rich frameworks, which is followed by the fabrication of composites through the incorporation of Cu₄SnS₄ (CSS) for dual electrochemical applications. Integrating CSS into the waste-derived carbon matrix induces strong synergistic effects, improving electrical conductivity, increasing active-site availability, and accelerating charge-transfer kinetics. Comprehensive physicochemical analyses confirmed the successful formation of a well-integrated heterostructure composite with favorable structural and surface characteristics. Electrochemical evaluations further demonstrated that CSS-modified carbon exhibits superior bifunctional performance. In a two-electrode configuration, the composite delivers an energy density of 12.08 Wh kg⁻¹ at a power density of 250 W kg⁻¹ along with excellent cycling stability in supercapacitor applications. As an electrocatalyst, it achieves a low overpotential of 268 mV at −10 mA cm⁻² and a small Tafel slope of 75 mV dec⁻¹, reflecting efficient reaction kinetics. The strong durability observed in both systems underscores the structural integrity and long-term operational stability of the material. Overall, this paper advances a sustainable waste-to-resource strategy for fabricating multifunctional carbon-based composites, offering a promising platform for integrated energy-storage and hydrogen-generation technologies. Full article

The pyrolysis of polypropylene (PP) microplastics offers a potential route to convert plastic waste into fuel-range hydrocarbon mixtures and chemical feedstocks. However, the elementary radical pathways underlying the formation of medium-chain hydrocarbon fragments remain insufficiently resolved. In this study, a representative isotactic PP oligomer model (C₄₅H₉₂) was evaluated using a comparative density functional theory (DFT) framework. The main mechanistic analysis was based on M06-2X, ωB97X-D, and M11 calculations combined with the def2-TZVP basis set, whereas LANL2DZ was retained only as a lower-cost comparative level during reaction-pathway exploration. Thermochemical profiles were evaluated over a temperature range of 298–923 K. Three selected pathways involving mid-chain homolytic cleavage, intramolecular hydrogen transfer (backbiting), radical rearrangement, and β-scission were examined. Within the selected reaction set, Route 1 exhibited a comparatively more favorable thermochemical profile than Routes 2 and 3 and provided a mechanistically plausible sequence toward medium-chain hydrocarbon fragments. The −TΔS contribution strongly influenced the calculated Gibbs free-energy profiles because fragmentation increases the number of molecular species under the ideal-gas thermochemical approximation. Accordingly, the ΔG values were interpreted comparatively and were not treated as direct evidence of spontaneous fragmentation under condensed-phase pyrolysis conditions or as quantitative predictions of experimental product selectivity. Differences among the evaluated functionals further indicate that the relative description of radical intermediates and transition-state regions is method-dependent. These results provide a molecular-level framework for future studies integrating quantum-chemical calculations, microkinetic modeling, and experimental product characterization. Full article

Hydrogen is a promising clean-energy carrier, but its low ignition energy, high diffusivity, and wide flammability range demand reliable leak detection. Chemiresistive sensors based on n-type metal oxide semiconductors are attractive owing to their simple architecture, low cost, large resistance modulation, thermal robustness, and compatibility with miniaturized devices. This review focuses on n-type metal oxide semiconductor nanomaterials for hydrogen sensing, particularly ZnO, SnO₂, In₂O₃, WO₃, TiO₂, and related mixed oxides. The fundamental sensing mechanisms are examined, including oxygen chemisorption, electron-depletion-layer modulation, grain-boundary barrier control, catalytic hydrogen spillover, and hydrogen-induced surface reduction or metallization, together with the way these mechanisms compete and cooperate under different operating conditions. Recent performance-enhancement strategies are organized around morphology and porosity control, noble-metal sensitization, defect and dopant engineering, n–n heterojunctions, molecular sieving, and low-temperature activation. Density functional theory is discussed as a design tool for evaluating adsorption energetics, vacancy formation, work-function shifts, band alignment, and interfacial charge transfer, along with its current limitations for modeling humid surfaces. Finally, key challenges and future directions, including humidity tolerance, standardized reporting, device integration, and emerging materials, are summarized to guide the development of high-performance hydrogen sensors. Full article

Transition-metal phosphides are promising non-noble-metal electrocatalysts for alkaline hydrogen evolution, yet further improving their performance remains challenging. In this work, a Co-doped nanoporous Fe₃P self-supported electrode was fabricated by vacuum high-frequency induction and melt spinning of Fe₇₅Co₅P₂₀ precursor alloys, followed by electrochemical dealloying. Nanoporous Fe₃P prepared from Fe₈₀P₂₀ was used as the reference. Structural analyses show that dealloying selectively removes the α-Fe phase while preserving the Fe₃P framework, resulting in a three-dimensional nanoporous architecture. XPS results further confirm successful Co incorporation and reveal that Co doping modifies the local chemical environment of Fe and P. Benefiting from the combined effects of Co incorporation and the nanoporous structure, np-Co-Fe₃P exhibits significantly improved HER performance in 1.0 M KOH, requiring only 70 mV to reach 10 mA cm⁻², much lower than that of np-Fe₃P (199 mV). In addition, np-Co-Fe₃P shows a smaller Tafel slope of 94 mV dec⁻¹, lower charge-transfer resistance, and a larger double-layer capacitance of 109.4 mF cm⁻². This work demonstrates an effective strategy for enhancing the alkaline HER performance of Fe-based phosphides through the combination of Co incorporation and dealloying-derived nanoporous architecture. Full article

Decarbonizing heavy-duty road transport requires comparing zero-emission options to guide infrastructure investments along strategic corridors. This study develops a scenario-based techno-economic model to evaluate hydrogen fuel cell trucks (HFCTs) and battery electric trucks supported by dynamic wireless power transfer (DWPT) on a 100 km segment of Italy’s A4 motorway in 2030 and 2050 scenarios. The framework integrates traffic flows, vehicle archetypes, infrastructure sizing, and end-to-end energy chains (power-to-hydrogen-to-wheel for hydrogen and grid-to-wheel for WPT) to estimate capital and operating costs, efficiencies, and energy demand. Results show that hydrogen refueling infrastructure requires lower initial investment (approximately €60 million CAPEX and €20 million annual OPEX) than wireless charging systems (€80 million CAPEX and €15 million OPEX). However, WPT achieves significantly higher grid-to-wheel efficiency (96% vs. 62%) and lower per-vehicle energy demand (18 MWh/year vs. 25 MWh/year). These findings highlight a fundamental trade-off: hydrogen solutions offer operational flexibility and are better suited to long-haul or low-density contexts, while WPT systems are more efficient and become increasingly competitive in high-traffic corridors with high infrastructure utilization. Overall, the results suggest that no single technology universally dominates and that optimal deployment depends on traffic density, infrastructure usage, and system integration. A combined implementation of hydrogen and wireless charging technologies may provide the most effective pathway to balance efficiency, flexibility, and cost in future heavy-duty transport systems. Full article

This study presents a phenomenological estimation framework for a membraneless alkaline water electrolyzer (MAWE), developed primarily from experimentally measured current signals and end-of-test mass-loss data. Thirteen KOH concentrations (5–35 g in 1 L deionized water) were investigated under a constant 12 V DC supply for 7200 s. The time-varying current was continuously recorded throughout each experiment, while the total gas production was determined from the net mass loss measured at the end of the electrolysis process. A time-resolved hydrogen-production representation was subsequently reconstructed from the measured current signal using Faraday’s law and constrained to be stoichiometrically consistent with the experimentally observed total mass loss. The term “charge-consistent” used throughout this study does not imply a new electrochemical principle, but rather refers to maintaining physical consistency between the experimentally measured current signal, Faraday-based charge transfer, and the experimentally observed end-of-test mass loss within the proposed phenomenological framework. Experimental results indicate that both the current response and the cumulative gas production exhibit a strong and distinctly nonlinear dependence on the KOH concentration. Two phenomenological modeling approaches were examined. The first is a static polynomial formulation describing the nonlinear relationship between the measured current signal and the reconstructed production rate. The second is a semi-empirical grey-box formulation in which the Faraday-based theoretical production term is corrected using an experimentally identified efficiency coefficient. Model performance was assessed using train/test data partitioning, residual analysis, autocorrelation functions, and Ljung–Box tests, demonstrating a high degree of internal charge consistency and macroscopic agreement with the reconstructed experimental representation. The proposed framework provides a reduced-order and experimentally accessible approach for representing reconstructed production behavior in MAWE systems without resorting to detailed multi-physics modeling or EIS-based characterization and offers a physically consistent baseline for comparison with more complex data-driven or control-oriented modeling strategies. Full article

During fast-fill, large type IV polymer composite hydrogen storage tanks experience significant temperature gradients associated with both the compression of the gas and a Joule–Thomson effect that can compromise vessel integrity, significantly affecting overall safety. In order to remedy this concern, the current work proposes a novel active mixing approach in which the tank rotates, which leads to enhanced internal convective heat transfer and consequently minimizes temperature gradients. Transient CF simulations were performed using the Redlich–Kwong real-gas equation of state, capturing the high-pressure thermodynamic behavior of hydrogen precisely. The study, based on the 1000 s fast-refueling of a tank of 20.56 m³ internal volume, was carried out to assess the tangential speeds of rotation at 10, 30, and 50 rad/s, respectively. Results also show that thermal performance has a strongly nonlinear dependence on rotational speed. At 10 rad/s, a reasonably even temperature profile develops with a much lower energy cost. The most significant suppression of peak temperatures, and therefore the most efficient cooling, is seen at 30 rad/s. Nevertheless, when the rotation speed further elevates to 50 rad/s, abundant viscous dissipation heating results in an unwanted secondary temperature increase while partially counteracting the benefits brought about by improved mixing. On the whole, the results indicate that an ideal operating window more closely correlated with 30 rads/s is seen to provide the most beneficial compromise between temperature uniformity, maximum temperature limitation, and energy consumption for rapid refueling of large composite hydrogen storage systems. Full article

Pt-based catalysts remain the premier hydrogen evolution reaction (HER) electrocatalysts for anion-exchange membrane water electrolyzers. Faced with insufficient abundance and high cost, developing low-Pt electrocatalysts that can accelerate the Volmer step while maintaining high durability is critically important yet challenging. Herein, we propose niobium nitrides with excellent conductivity and stability as supports for Pt to enhance the alkaline HER. A polyoxoniobate-based molecular self-assembly strategy was ingeniously designed to fabricate Nb₄N₅ nanospheres, on which ultrafine Pt nanoparticles (NPs) were successfully immobilized, forming Pt/Nb₄N₅ heterostructures (denoted as Pt/Nb₄N₅). The rich interface structures with metal–support interactions drive charge transfer from Pt to Nb₄N₅, which modulates the electronic structure of Pt and Nb sites, collectively lowering interfacial charge transfer resistance, generating abundant active sites, and improving catalyst durability. Consequently, the Pt/Nb₄N₅ catalyst achieves exceptional HER performance, including a low overpotential (22 mV@10 mA cm⁻²), a small Tafel slope (26 mV dec⁻¹), an 11.5-fold higher mass activity at 150 mV, and remarkable durability, drastically surpassing the commercial Pt/C catalyst. Notably, the Pt/Nb₄N₅-based electrolyzer requires only 1.508 V to drive 10 mA cm⁻². This work offers a viable pathway to engineer highly active and durable low-Pt electrocatalysts for energy-related applications. Full article

Focusing on the thermodynamic response of onboard liquid hydrogen tanks under dynamic sloshing conditions, this study investigates the flow-thermal coupling mechanism between the gas-phase space and the main chamber by establishing a numerical model that includes the gas-phase space. The results show that the gas-phase space enhances the initiative and efficiency of system pressure regulation through pressure-difference-driven mass transfer. The evolution of the gas–liquid two-phase temperature field sequentially undergoes four typical stages: pressure-difference-driven jet dominance, thermal stratification maintenance, turbulent mixing, and thermal stratification disappearance. The magnitude of the initial pressure difference significantly affects the temperature response and pressure equilibration time of the two chambers. The gas-phase space achieves thermal uniformity in approximately 4.1 s under sloshing, demonstrating its role as a “dynamic thermal buffer.” The research reveals the critical function of the gas-phase space in the dynamic thermal management of liquid hydrogen storage tanks, providing guidance for enhancing the safety and stability of the onboard hydrogen storage system. Full article

This work presents a case study of sensitivity analysis applied to the modeling of ethanol steam reforming (SRE) in a catalytic porous medium, with a focus on hydrogen production. Considering the high variability of parameters reported in the literature, the objective is not to propose a universal model, but rather to assess the impact of uncertainties associated with input parameters on the model outcomes. The model was developed under steady-state conditions, coupling flow in porous media, species transport, and heat transfer, with kinetics described as a function of partial pressures. The sensitivity analysis was conducted through the systematic variation of kinetic and physicochemical parameters within ranges associated with their uncertainties. The results indicate that activation energy is the parameter most sensitive to uncertainty variation, exhibiting the greatest impact on hydrogen production. The thermal properties of the medium, particularly thermal conductivity and solid density, also stand out, highlighting the role of thermo-kinetic coupling. In contrast, parameters such as porosity, water reaction order, and particle diameter exhibited low sensitivity under the analyzed conditions. As a main contribution, this work establishes a sensitivity hierarchy associated with parameter uncertainties and provides guidance for other researchers regarding the prioritization of their determination and calibration in hydrogen production models. Full article

Persistent organic contaminants and complex wastewater matrices challenge conventional treatment because parent-compound removal does not necessarily imply mineralization, detoxification, or improved environmental safety. Advanced oxidation processes can address these limitations, but practical effectiveness is often constrained by oxidant activation, gas–liquid mass transfer, reagent distribution, light penetration, catalyst contact, energy demand, and matrix scavenging. This work critically examines hydrodynamic cavitation-assisted advanced oxidation processes for water and wastewater treatment, including systems based on hydrogen peroxide, ozone, Fenton and Fenton-like reactions, persulfate, peroxydisulfate, peroxymonosulfate, UV irradiation, photocatalysis, cold plasma, multi-hybrid configurations, and emerging reduction-oriented approaches. The discussion covers reactor configurations, target contaminants, real matrices, and sustainability-related performance metrics. The central argument is that hydrodynamic cavitation is not automatically sustainable as a stand-alone treatment. It becomes relevant as a sustainable intensification module only when measurable improvements are demonstrated in oxidant activation, mass transfer, treatment depth, biodegradability, toxicity reduction, process integration, or scale-up at acceptable energy and chemical cost. A reporting framework is proposed based on mineralization, COD/TOC reduction, by-products, toxicity, biodegradability, normalized energy consumption, chemical efficiency, real-matrix validation, reproducibility, and cost-relevant indicators. Future progress should move from isolated degradation tests to integrated, controllable, and scalable treatment frameworks. Full article

A comparative density functional theory (DFT) study was performed to elucidate the mechanistic details of Schiff base formation between 3-pyridinecarboxaldehyde and the three positional isomers of aminobenzoic acid (o-, m-, and p-). Both single proton transfer (SPT) and methanol-assisted double proton transfer (DPT) pathways were systematically investigated in the gas phase and within a polarizable continuum model (PCM) for methanol. All stationary points were optimized at the B3LYP/6-31G and 6-311++G(d,p) levels, and transition states were confirmed by vibrational frequency and intrinsic reaction coordinate (IRC) analyses. The results reveal that the DPT mechanism is consistently associated with significantly lower activation free energies compared to the direct SPT pathway, particularly in methanol, where solvent-mediated proton relay markedly stabilizes the transition states. The positional effect of the amino group influences both the electrostatic potential distribution and the activation barriers, with the para isomer exhibiting enhanced nucleophilicity and improved reaction efficiency. These findings provide detailed mechanistic insight into solvent-assisted proton transfer processes in Schiff base synthesis and highlight the cooperative role of hydrogen-bond networks in reducing energetic barriers. Full article