Search Results (1,162)

Electrolysis of water is a promising emission-free approach of hydrogen production, making water electrolyzers important for many renewable energy systems. Electrochemical electrodes enriched with nanocatalysts can significantly advance such technologies, but the use of nanomaterials, deployed as packed powders or painted films, is generally limited by durability and reusability challenges. To overcome these deficiencies, we have fabricated hierarchical hybrid electrode (HHE) monoliths comprising carpet-like arrays of multiwalled carbon nanotubes covalently bonded to porous reticulated carbon foams that are further functionalized with strongly attached nanocatalysts. This paper presents our investigation of HHE materials with CNT carpets and palladium nanoparticle (PdNP) catalysts in two key electrolysis reactions: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Their performances in different electrolytes have been evaluated using cyclic voltammetry, linear sweep voltammetry and Tafel analysis. This architecture provided multi-faceted advantages, and the contribution of each nanocomponent in the monolith has been analyzed. The presence of Pd-NP in the HHE also improved the electrode’s tolerance to Cl⁻ ions, which is very promising for saline water electrolysis. These studies indicate that the HHE architecture of electrochemical electrodes can be a versatile and tunable option for future electrochemical systems relevant to renewable energy applications. Full article

Water electrolysis has emerged as a strategically appealing route for the sustainable production of green hydrogen (H₂) via the hydrogen evolution reaction (HER), though the sluggish kinetics of the oxygen evolution reaction (OER) remains a bottleneck hindering large-scale practical applications. In this regard, an attractive solution is offered by the integration of the ethanol oxidation reaction (EOR) into hybrid water-splitting systems, favorably reducing anodic overpotentials. Nonetheless, an open challenge is related to the fabrication of eco-friendly and economically viable catalysts free from noble metals, combining efficiency and stability. Herein, we explore nickel-oxide-based nanostructures grown onto porous Ni foam scaffolds by a scalable hydrothermal (HT) approach as EOR electrocatalysts. Material properties arising from modulation of the sole HT growth time are investigated by complementary structural, microscopic, and spectroscopic techniques. Electrochemical tests demonstrate good durability and very attractive EOR performances, mainly influenced by the morphology and the NiOOH surface content of the target systems. Overall, the present work advances an attractive route to transition-metal-based electrocatalysts for efficient alcohol-oxidation-assisted water electrolysis. Full article

The world’s growing need for energy, fueled by industrial expansion and a rising population, continues to be a challenge for the scientific community. The heavy reliance on fossil fuels that contribute to environmental degradation and public health concerns, is shifting toward sustainable alternatives, with hydrogen production via advanced catalysts as an energy source emerging as a promising solution. This transition addresses the challenges posed by harmful combustion emissions. In this study, we developed an innovative PANI@Cu-NA-MOF nanocomposite catalyst through a sol–gel synthesis approach that strategically integrates conducting polymers with metal–organic frameworks. The catalyst was characterized using different sets of techniques. Surface morphology and elemental composition were investigated using SEM-EDX, while structural analysis was carried out with FTIR that helped to identify the chemical bonds and functional groups, and UV-Vis spectroscopy provided information on its light absorption properties. In addition, TGA was used to evaluate thermal behavior, and XPS offered detailed surface chemical analysis. It was observed by morphology that PANI@Cu-NA-MOF is a noncapsular-like structure. It is thermally highly stable; a TGA study showed that up to 550 °C, almost 2.5% of weight was lost. The single peak in UV-Vis is the preparation of a successful composite. XPS and FTIR reveal the required peaks of functional groups and elements. The PANI@Cu-NA-MOF composite turned out to be quite effective for water electrolysis, requiring an overpotential of just 0.47 V to drive the reaction. When tested against the reversible hydrogen electrode, we observed onset potentials of 1.6 V/RHE for the oxygen evolution reaction and 0.2 V/RHE for the hydrogen evolution reaction. What makes this particularly interesting is that such performance significantly cuts down on the energy needed for electrolysis, which could make hydrogen production much more practical. Since hydrogen burns cleanly and offers a real alternative to fossil fuels, having an efficient catalyst like this brings us one step closer to sustainable energy. Full article

Hydrogen-based reduction of manganese ores has attracted increasing attention as a promising route for low-carbon manganese production. In this study, the reduction behavior, microstructural evolution, and kinetics of a high-barium-rich manganese ore were investigated in both dried and calcined states under isothermal hydrogen atmospheres at 600–800 °C. The ore was characterized using XRF, XRD, optical microscopy, SEM-EDS, and porosity measurements to evaluate mineralogical and structural changes during calcination and reduction. Calcination at 900 °C transformed MnO₂ into Mn₂O₃/Mn₃O₄, removed volatile components, and generated micro-porosity that improved gas accessibility. Isothermal reduction experiments revealed a rapid initial reduction stage followed by a slower reaction regime, with increasing temperature significantly accelerating the reduction rate. Despite isothermal furnace conditions, a temporary rise in sample temperature was observed due to the exothermic nature of manganese oxide reduction by hydrogen. XRD analysis confirmed that manganese oxides were predominantly reduced to MnO, while iron oxides were converted to metallic Fe. Porosity measurements showed significant pore development during reduction at moderate temperatures due to oxygen removal and gas evolution; however, at higher temperatures, partial sintering led to pore coalescence and densification, reducing the overall porosity. Kinetic analysis showed that the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model effectively describes the reduction behavior. The apparent activation energies were 21.92 kJ.mol⁻¹ for dried ore and 17.40 kJ.mol⁻¹ for calcined ore, indicating diffusion-influenced kinetics. The results demonstrate that calcination enhances hydrogen reducibility by improving gas accessibility and reducing kinetic resistance, highlighting its importance for hydrogen-based manganese pre-reduction processes. Full article

Electrocatalytic H₂O₂ production via the two-electron oxygen reduction reaction (ORR) is a highly sustainable alternative to industrial methods. To further optimize non-noble catalysts, we report an interfacial engineering strategy to stabilize the metastable P6₃/mmc-La₂O₃ phase on SrTiO₃. This symmetry evolution from the low-symmetry $\mathrm{P}\stackrel{\mathrm{-}}{3}\mathrm{m}1$ (trigonal) to the high-symmetry P6₃/mmc (hexagonal) space group yields a composite with >95% H₂O₂ selectivity. Mechanistic studies demonstrate that the symmetry-regulated interface optimizes *OOH conversion and suppresses O–O bond cleavage. This work offers a robust design principle for high-performance, noble-metal-free H₂O₂ electrosynthesis. Full article

The efficiency of hydrogen production via water electrolysis is severely constrained by the sluggish reaction kinetics of the oxygen evolution reaction (OER). Herein, we constructed a nitrogen-doped CoFe Prussian blue analog (CoFePBA-N) electrocatalyst with a nanosheet-assembled cubic architecture by plasma. Plasma treatment induces morphological reconstruction and introduces nitrogen dopants and abundant vacancies, which not only increase the number of exposed active sites but also modulate the electronic structure of Co/Fe centers. Consequently, the optimized CoFePBA-N catalyst achieves a current density of 500 mA cm⁻² at low overpotentials of 322, 344, and 374 mV in alkaline freshwater, alkaline simulated seawater, and alkaline natural seawater, respectively. Furthermore, the catalyst maintains stable operation for over 300 h in alkaline freshwater and nearly 270 h in alkaline natural seawater, exhibiting exceptional durability. The enhanced catalytic performance is attributed to the synergistic effects of nitrogen doping, vacancies, and improved charge-transfer capability. This study provides an effective approach for modulating the electronic structure of Prussian blue analogs, thereby enabling efficient alkaline water and seawater electrolysis. Full article

Developing effective metal-free electrocatalysts for acidic hydrogen evolution is challenging because both catalytic activity and electronic conductivity must be optimized simultaneously. Here, h-BN/carbon nano-onion (CNO) hybrid electrocatalysts were synthesized by integrating layered hexagonal boron nitride with conductive carbon nano-onions to generate accessible heterointerfaces for the hydrogen evolution reaction (HER). Structural characterization by XRD, SEM/TEM, and STEM-EDS confirmed intimate contact between h-BN sheets and quasi-spherical CNO domains. Similarly, XPS revealed B–N-rich frameworks with interfacial B–C/C–N surface environments and oxygen-associated defect sites. Among the prepared compositions, the h-BN/CNO20 eletrocatalyst exhibited the best apparent HER performance in 0.5 M H₂SO₄, delivering an overpotential of ~270 mV at 5 mA cm⁻² and a Tafel slope of 76 mV dec⁻¹, along with stable chronoamperometric behavior for 15 h. The improved electrocatalytic activity is due to the enhanced charge transport through the CNO network, suppression of h-BN restacking, increased exposure of interfacial sites, and charge redistribution across B–N/C heterojunctions. These findings identify h-BN/CNO20 as the optimum composition within this series and demonstrate that heterointerface engineering between boron nitride and curved graphitic nanocarbons is a promising strategy for developing metal-free HER electrocatalysts. However, further validation using a non-Pt counter electrode is necessary to confirm intrinsic catalytic activity. Full article

Electrochemical chlorine production is of considerable industrial importance in areas such as water treatment, chemical manufacturing, and disinfection. However, conventional precious metal-based dimensionally stable anodes (DSAs), such as RuO₂- and IrO₂-based systems, are limited by high cost and resource constraints, motivating the development of low-cost alternative catalysts. In this study, Mn₃O₄ electrodes with controllable defect characteristics were fabricated by electrochemical deposition under various processing conditions. The effects of defect modulation and surface modification on the structural, electronic, and electrochemical properties of the electrodes were systematically evaluated. X-ray diffraction analysis confirmed that all deposited films retained a stable tetragonal Mn₃O₄ crystal structure, indicating that the deposition parameters primarily influenced defect states rather than the bulk phase. Mott–Schottky measurements revealed that the Mn₃O₄ electrodes exhibited p-type semiconducting behavior, with charge carrier densities on the order of 10¹⁴ cm⁻³, suggesting that oxygen vacancy-related defect states may contribute to the observed electronic properties of the electrodes. To further enhance anodic performance, Pt was introduced onto the Mn₃O₄ surface via sputtering, resulting in significantly improved charge transfer characteristics. Electrochemical measurements demonstrated that the best performing Pt/Mn₃O₄ electrodes delivered a current density exceeding 100 mA cm⁻² at an applied potential of 1.5 V versus Ag/AgCl. More importantly, defect-enriched Pt/Mn₃O₄ electrodes exhibited markedly enhanced chlorine evolution activity, with the chlorine production rate increasing from approximately 14 µmol cm⁻² to 29 µmol cm⁻², corresponding to an enhancement of about 2.07-fold. Faradaic efficiency analysis further showed that sample (g) and sample (n) achieved chlorine evolution efficiencies of 59.2% and 74.6%, respectively, indicating a higher tendency toward chlorine evolution for the Pt-modified electrodes under the tested conditions. These findings suggest that the synergistic combination of defect engineering and surface modification effectively modulates the electronic structure of Mn₃O₄, providing a viable strategy for improving chlorine evolution performance. Full article

Wine bottle aging is governed by complex redox reactions involving phenolic compounds, oxygen transfer and storage conditions, which collectively determine the evolution of wine composition and sensory properties. This review critically examines the main oxidative mechanisms responsible for bottle aging and evaluates traditional and emerging strategies aimed at modulating the evolution of wine. Particular attention is paid to oxygen management, cork type, temperature and light exposure, as well as alternative approaches such as accelerated aging techniques and underwater storage. The available evidence suggests that most accelerated aging technologies fail to replicate the chemical pathways of natural in-bottle aging, often resulting in different aromatic profiles. Attention is paid to underwater aging, an emerging practice that combines specific conditions of temperature, light and limited oxygen availability. The results of the available studies indicate that underwater aging does not significantly alter the basic chemical parameters of wine, but can modulate its phenolic, chromatic and sensory evolution, suggesting a slowdown in oxidative processes compared to traditional aging in the cellar. Full article

The rational design of cost-effective and highly active electrocatalysts for overall water splitting remains a critical challenge for sustainable hydrogen production. Herein, we report a two-dimensional reduced graphene oxide (rGO)-supported Mo₂S₃ nanohybrid catalyst with a tunable electronic structure engineered through interfacial coupling. The intimate integration of Mo₂S₃ nanoflakes with conductive rGO nanosheet facilitates rapid electron transport, enhanced active site exposure, and optimized adsorption energetics for reaction intermediates. Structural and spectroscopic analyses confirm strong electronic interaction between Mo₂S₃ and rGO, leading to modulated charge density distribution and improved intrinsic catalytic activity. Electrochemical evaluations reveal significantly reduced overpotentials for oxygen evolution reaction (OER) with 166 mV overpotential at 10 mA cm⁻² current density, along with favorable Tafel kinetics with 38.1 mV dec⁻¹ and long-term operational stability in alkaline electrolyte. The rGO-Mo₂S₃-2||Pt-C cell delivers 10 mA cm⁻² at 1.64 V, indicating efficient alkaline water splitting. The enhanced performance is attributed to synergistic effects arising from electronic modulation, enhanced active sites, and accelerated interfacial charge transfer. Full article

The oxygen evolution reaction (OER), serving as the anodic bottleneck in electrochemical water splitting for hydrogen production, severely limits the overall energy conversion efficiency due to its sluggish kinetics. Developing efficient and stable electrocatalysts based on earth-abundant elements is a critical challenge for advancing clean energy technologies. In recent years, silicate materials have demonstrated significant potential in alkaline OER catalysis owing to their unique stable silicon-oxygen tetrahedral framework and flexibly tunable metal-oxygen-silicon electronic coordination environments. This review systematically summarizes recent progress in silicate-based materials, including natural clay mineral supports such as halloysite, for OER electrocatalysis. It focuses on controllable synthesis strategies for silicate materials and provides an in-depth analysis of the regulation mechanisms for their electronic structure and surface properties through defect engineering, anion vacancy construction, and bimetallic/non-metallic heteroatom doping. Particular emphasis is placed on research pathways that utilize natural silicate clay minerals as both supports and silicon sources to construct high-performance composite catalytic materials via innovative structural design and interface engineering. Systematic studies indicate that precisely modulated silicate-based catalysts exhibit excellent electrochemical activity and long-term stability in the alkaline OER process. This review offers perspectives on the future development of efficient and stable silicate-based catalytic systems for renewable energy conversion. Full article

This study elucidates the mechanism enabling the low-voltage electrolysis of black liquor (BL) for integrated resource recovery. The process simultaneously generates protons at the anode via the oxidation of organics (OOR), which occurs at a lower potential than the oxygen evolution reaction (OER), and induces lignin precipitation. Concurrently, hydrogen and hydroxide ions are produced at the cathode through the hydrogen evolution reaction (HER). Driven by the electric field, sodium ions migrate from the anode to the cathode chamber, combining with hydroxide ions to form sodium hydroxide, thereby achieving the synchronous production of acid, alkali, hydrogen, and modified lignin in a single process. Using a platinum electrode, we conducted a mechanistic investigation through linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and detailed product analysis. The results show that overall efficiency is controlled by competition at the anode between OOR and OER, which directly determines proton yield. A critical trade-off exists between anodic proton generation and cathodic alkali recovery, driven by the competitive migration of protons and sodium ions across the cation-exchange membrane. The proton yield was highly dependent on the initial BL composition, with a characteristic peak observed under specific conditions. Conversely, the sodium hydroxide recovery rate was maximized when the anolyte pH remained high, minimizing competitive proton migration. This work provides fundamental insights into the interfacial mechanisms of BL electrocatalytic, establishing it as a versatile electrochemical biorefinery platform for simultaneous proton and alkali production from a renewable waste stream, beyond its role as a hydrogen source and lignin recovery. Full article

The electrochemical CO₂ reduction reaction (CO₂RR) offers a sustainable route for converting greenhouse gases into high-value fuels; however, its efficiency has long been constrained by the thermodynamic stability of CO₂ molecules and the competing hydrogen evolution reaction. Using density functional theory (DFT) calculations, this work systematically investigates the catalytic performance of Ni₅ and alloy Ni₄Cu clusters anchored on divacancy graphene (DVG) for CO₂RR. The results demonstrate that the introduction of Cu atoms significantly enhances the interfacial binding energy between the cluster and the support (shifting from −6.2 eV to −7.5 eV). Charge density difference analysis combined with Bader charge analysis further reveals that interfacial charge transfer and the formation of Ni–C bonds serve as the electronic origin of this improved stability. Free energy calculations show that, compared to Ni₅/DVG, Ni₄Cu/DVG substantially reduces the energy barrier of the rate-determining step for formic acid (HCOOH) formation from 1.18 eV to 0.26 eV, thereby significantly optimizing the reaction kinetics. Crystal orbital Hamilton population (COHP) analysis demonstrates that Cu doping modulates metal–oxygen bond strength in the key *OCHO intermediate (ICOHP: Ni-O bonds at −0.697 eV/−0.976 eV vs. Cu-O bonds at −0.408 eV/−0.492 eV), optimizing the adsorption–desorption balance and steering selectivity toward HCOOH. This work elucidates the atomic-scale electronic and bonding mechanisms underlying Ni–Cu synergistic effects, providing theoretical guidance for designing efficient non-noble metal CO₂RR electrocatalysts. Full article

Developing active and robust catalysts for the acidic oxygen evolution reaction (OER) with reduced Ir loading is still a challenge in the industrial production of green H₂. In this work, several catalysts ranging from single metal oxides (e.g., IrO₂) to high-entropy oxides (IrNiMnFeCoCuVO_x) were synthesised through thermal decomposition in air to study the effect of the mixed-oxide composition in terms of activity and stability towards the acidic OER. Catalysts were named MOx-n, with n being the number of metal elements in the mixture. The results show that the activity of rutile IrO₂ can be improved by introducing other elements into the composition. The best performance was obtained for MOx-4 to MOx-5, which delivered a current density of 10 mA cm⁻² at an overpotential (η₁₀) of 279 ± 4 mV; approx. 100 mV lower than IrO₂ at a comparable Ir loading and with better stability. Nevertheless, further increasing the complexity of the mixed oxide resulted in an evident degradation in terms of activity and stability. It is worth noting that surface dissolution and reconstruction occurred with all mixed-oxide catalysts, including high-entropy configurations. Full article

Mixed-halide perovskite solar cells with the composition Cs_0.1(MA_0.17FA_0.83)_0.9Pb(I_0.83Br_0.17)₃ were fabricated obtaining solar cells as glass/ITO/SnO₂/triple-cation perovskite/HTL/Au, and subsequently used as photoanodes for efficient solar-driven water splitting by attaching commercial catalytic nickel foils to the Au back-contact pads of solar cells. To enable operation in alkaline media, the devices were encapsulated using commercial PET–EVA multilayer films, providing an effective barrier while leaving the Ni foils exposed as the electrochemically active interface. Two operating configurations were investigated and compared: (i) an outside configuration, where the perovskite device powered the external electrochemical cell, and (ii) an immersed configuration, in which the encapsulated perovskite solar cell was directly integrated, together with the Ni catalyst, into the electrolyte. In both configurations, the onset potential for the oxygen evolution reaction shifted from ~1.32 V vs. RHE, when the Ni electrode was not powered by the perovskite solar cell, to ~0.34 V vs. RHE, when the perovskite device powered the Ni foil for both immersed and outside configurations. The immersed configuration delivered the highest performance, achieving a maximum Applied Bias Photon-to-Current Efficiency of ~20% under AM 1.5 G illumination (100 mW cm⁻²), among the highest values reported for perovskite-based photoanodes. Importantly, the enhanced performance does not arise from changes in catalyst composition or direct semiconductor–electrolyte interaction, but from improved photovoltage delivery and reduced resistive losses enabled by the integrated device architecture. These results demonstrate that device architecture is a key factor in controlling photovoltage utilization and charge-transfer kinetics, providing a viable strategy for efficient and scalable perovskite-based photoelectrochemical systems. Full article