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Two new supramolecular photocatalysts made of covalently linked Ru(II) polypyridine chromophore subunits ([Ru(bpy)3]2+-type species; bpy = 2,2′-bipyridine) and [RuL(pic)2] (L = 2,2′-bipyridine-6,6′-dicarboxylic acid; pic = 4-picoline) water oxidation catalyst subunits have been prepared. The new species, 1 and 2, contain chromophore and catalyst subunits in the molecular ratios 1:1 and 1:2, respectively. The model chromophore species [Ru(bpy)2(L1)]2+ (RuP1; L1=4-[2-(4-pyridyl)-2-hydroxyethyl]-4-methyl-2,2′-bipyridine) and [Ru(bpy)2(L2)]2+ (RuP2; L2 = 4,4′-bis[2-(4-pyridyl)-2-hydroxyethyl]-2,2′-bipyridine) have also been prepared. The absorption spectra, oxidation behavior, and luminescent properties of 1 and 2 have been studied, and the results indicate that each subunit largely maintains its own properties in the supramolecular species. However, the luminescence of the chromophore subunits is significantly quenched in 1 and 2 in comparison with the luminescence of the respective model species. Both 1 and 2 exhibit catalytic water oxidation in the presence of cerium ammonium nitrate, exhibiting an I2M mechanism, with a better efficiency than the known catalyst [RuL(pic)2] under the same experimental conditions. Upon light irradiation, in the presence of persulfate as a sacrificial acceptor agent, 1 and 2 are more efficient photocatalysts than a system made of separated [Ru(bpy)3]2+ and [RuL(pic)2] species, highlighting the advantage of using multicomponent, supramolecular species with respect to isolated species. The O–O bond formation step is I2M, even in the photo-driven process. The photocatalytic process of 2 is more efficient than that of 1, with the turnover frequency reaching a value of 1.2 s−1. A possible reason could be an increased local concentration of catalytic subunits in the needed bimolecular assembly required for the I2M mechanism in 2 with respect to 1, a consequence of the presence of two catalytic subunits in each multicomponent species 2. [ABSTRACT FROM AUTHOR]

Understanding the protonation behavior of metal-oxo water oxidation catalysts is essential to improve catalyst efficiency and long-term performance, as well as to tune their properties for specific applications. In this work, we explore the basicity and protonation effects of the highly active water oxidation catalyst [(Mn4O4) (V4O13) (OAc)3]3− using density functional theory. We computed the relative free energies of protonation in a systematic fashion for all symmetry-inequivalent O atoms, where the presence of multiple oxidation states from Mn 4 IV to Mn 4 III and a rich Jahn–Teller isomerism adds a significant amount of complexity. For high oxidation states, the compound behaves like some other polyoxometalates, showing protonation preferably at the terminal and μ2-bridging O atoms of the vanadate cap. However, upon reduction, eventually, the protonation preference switches to the cubane O atoms, mostly driven by a strong increase in basicity for O atoms located along the Jahn–Teller axes. Our work further evidences that protonation can potentially lead to several chemical transformations, like disproportionation and charge transfer to vanadium, dissociation of ligands, or the opening of the cubane structure. Our simulated UV/Vis absorption spectra additionally provide valuable insights about how the protonation of the catalyst could be tracked experimentally. Overall, our analysis highlights the complexity involved in the protonation of heterometallic polyoxometalate clusters. [ABSTRACT FROM AUTHOR]

The sluggish oxygen evolution reaction (OER) in overall electrocatalytic water splitting poses a significant challenge in hydrogen production. A series of transition metal phosphides are emerging as promising electrocatalysts, effectively modulating the charge distribution of surrounding atoms for OER. In this study, a highly efficient OER electrocatalyst (CoP-CNR-CNT) was successfully synthesized through the pyrolysis and phosphatization of a Co-doped In-based coordination polymer, specifically InOF-25. This process resulted in evenly dispersed CoP nanoparticles encapsulated in coordination polymer-derived carbon nanoribbons. The synthesized CoP-CNR-CNT demonstrated a competitive OER activity with a smaller overpotential (η10) of 295.7 mV at 10 mA cm-2 and a satisfactory long-term stability compared to the state-of-the-art RuO2 (η10 = 353.7 mV). The high OER activity and stability can be attributed to the high conductivity of the carbon network, the abundance of CoP particles, and the intricate nanostructure of nanoribbons/nanotubes. This work provides valuable insights into the rational design and facile preparation of efficient non-precious metal-based OER electrocatalysts from inorganic–organic coordination polymers, with potential applications in various energy conversion and storage systems. [ABSTRACT FROM AUTHOR]

The development of robust and efficient photocatalytic constructs for boosting the water oxidation reaction (WOR) is needed for establishing a sunlight-driven renewable energy infrastructure. Here, we synthesized plasmonic core–shell nanoconstructs consisting of triangular gold nanoprism (AuTNP) core with mixed manganese oxide (MnOx) shell for photoelectrocatalytic WOR. These constructs show electrocatalytic WOR with a low onset overpotential requirement of 270 mV at pH 10. Photoexcitation showed further enhancement of their catalytic activity resulting in ∼15% decrease of the onset overpotential requirement along with the generation of photocurrent density of up to 300 μA/cm2. We showed that such light-driven enhancement of AuTNP@MnOx dyad's catalytic activity toward the WOR process includes contributions from both photocatalytic (hot carriers driven) and photothermal effects with photothermal effect playing the major role for wavelength between 532 and 808 nm. The contribution from the photocatalytic effect is appreciable only for high-energy excitations near the interband region, while the photothermal effect largely dominates for lower energy excitations near the LSPR wavelengths of the dyad. [ABSTRACT FROM AUTHOR]

The development of an ideal photoanode that exhibits broad light absorption, efficient photogenerated carrier separation, and superior transmission efficiency remains a pivotal challenge in enhancing the sluggish photoelectrochemical (PEC) water splitting reaction. Here, we present an efficacious strategy to bolster the PEC performance of oxygen evolution by fabricating a BiVO 4 /BiOBr heterojunction through a combined electrochemical deposition-calcination approach and the successive ionic layer adsorption and reaction (SILAR) method. The band structure of BiOBr is optimally aligned with BiVO 4 , enabling the heterojunction to significantly enhance the separation efficiency of photogenerated charges and accelerate the kinetics of PEC water oxidation. Under simulated sunlight irradiation, the BiVO 4 /BiOBr heterojunction exhibits a remarkable photocurrent density of 2.69 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE), surpassing the performance of bare BiVO 4 film (0.46 mA/cm2 at 1.23 V vs. RHE) and demonstrating exceptional stability. This work offers novel insights into the rational design and fabrication of solar-driven PEC water splitting photoanodes. [Display omitted] • A type-II heterojunction was constructed between BiVO 4 and BiOBr. • Heterojunction promotes the transmission of photogenerated charge in and on the surface of photoanode bulk phase. • Heterojunction improves the optical absorption range and enhances the photogenerated charge separation. [ABSTRACT FROM AUTHOR]

This study investigates the effects of boron nitride (BN) coating characteristics on the subsurface oxidation behavior of SiC/SiC composites in high‐temperature, water‐rich environments. Three types of coatings were examined: a crystalline stoichiometric BN, an amorphous BN, and a Si‐doped amorphous BN, the latter two containing 5–10 at% of oxygen and carbon. High‐resolution imaging and chemical analysis techniques were used to probe microstructural changes after oxidation at 1000°C for 1 or 12 h in flowing 20 vol% H2O, focusing on effects of coating thickness. Complementary chemical thermodynamic calculations and models for reaction‐ and transport‐controlled recession were used to interpret the experimental findings. Crystalline BN coatings produce open recession channels without forming borosilicate glass, a consequence of carbothermal reduction arising from C/CO produced through concomitant SiC oxidation. The combination of active oxidation and the relatively thick coatings in this system (ca. 1 µm) leads to a recession rate controlled by the intrinsic BN volatilization rate rather than the rate of gas transport. In contrast, amorphous coatings, both undoped and Si‐doped, readily oxidize to form borosilicate glasses that replace the BN. Broadly, the recession lengths increase with coating thickness. In the early stages, while the glass is boria‐rich and thus permeable to environmental oxidants, recession is controlled by the BN oxidation rate. As boria volatilizes, the silica concentration in the glass increases, eventually reaching the saturation limit and precipitating solid silica on the internal surfaces, essentially arresting further recession. [ABSTRACT FROM AUTHOR]

The productions of hydrogen peroxide (H2O2) and hydrogen (H2) in a photoelectrochemical (PEC) water splitting cell suffer from an onset potential that limits solar conversion efficiencies. Moreover, the formation of H2O2 through two‐electron PEC water oxidation reaction competes with four‐electron oxidation evolution reaction. Herein, we developed the surface selenium doped antimony trisulfide photoelectrode with the integrated ruthenium cocatalyst (Ru/Sb2(S,Se)3) to achieve the low onset potential and high Faraday efficiency (FE) for selective H2O2 production. The photoanode exhibits an outstanding average FE of 85 % in the potential range of 0.4–1.6 VRHE and the H2O2 yield of 1.01 μmol cm−2 min−1 at 1.6 VRHE, especially at low potentials of 0.1–0.55 VRHE with 80.4 % FE. Impressively, an unassisted PEC system that employs light and electrolyte was constructed to simultaneously produce H2O2 and H2 production on both the Ru/Sb2(S,Se)3 photoanode and the Pt/TiO2/Sb2S3 photocathode. The integrated system enables the average PEC H2O2 production rate of 0.637 μmol cm−2 min−1 without applying any addition bias. To our knowledge, this is the first demonstration that Sb2S3‐based photoelectrodes exhibit H2O2/H2 two‐side production with a strict key factor of the system, which represents its powerful platform to achieve high efficiency and productivity and the feasibility to facilitate value‐added products in neutral conditions. [ABSTRACT FROM AUTHOR]

The precise regulation of single‐atom catalysts (SACs) with the desired local chemical environment is vital to elucidate the relationship between the SACs structure and the catalytic performance. The debate on the effect of the local coordination environment is quite complicated even for the SACs with the same composition and chemical nature, calling for increased attention on the regulation of the second coordination shell. For oxide‐supported SACs, it remains a significant challenge to precisely manipulate the second coordination shell of single atoms supported on oxides due to the structural robustness of oxides. Here, Ir single atoms were anchored on NiO supports via different bonding strategies, resulting in the diverse Ir−O−Ni coordination numbers for Ir sites. Specifically, Ir1/NiO, Ir1−NiO, and Ir1@NiO SACs with increasing Ir−O−Ni coordination numbers of 3, 4, and 5 were synthesized, respectively. We found that the activity of the three samples towards oxygen evolution reaction (OER) exhibited a volcano‐shaped relationship with the Ir−O−Ni coordination number, with Ir1−NiO showing the lowest overpotential of 225 mV at 10 mA cm−2. Mechanism investigations indicate that the moderate coordination number of Ir−O−Ni in Ir1−NiO creates the higher occupied Ir dz2 orbital, weakening the adsorption strength for *OOH intermediates and thereby enhancing the OER activity. [ABSTRACT FROM AUTHOR]

The pursuit of carbon‐neutral energy has intensified the interest in green hydrogen production from direct seawater electrolysis, given the scarcity of freshwater resources. While Ni‐based catalysts are known for their robust activity in alkaline water oxidation, their catalytic sites are prone to rapid degradation in the chlorine‐rich environments of seawater, leading to limited operation time. Herein, we report a Ni(OH)2 catalyst interfaced with laser‐ablated LiFePO4 (Ni(OH)2/L‐LFP), derived from spent Li‐ion batteries (LIBs), as an effective and stable electrocatalyst for direct seawater oxidation. Our comprehensive analyses reveal that the PO43− species, formed around L‐LFP, effectively repels Cl− ions during seawater oxidation, mitigating corrosion. Simultaneously, the interface between in situ generated NiOOH and Fe3(PO4)2 enhances OH− adsorption and electron transfer during the oxygen evolution reaction. This synergistic effect leads to a low overpotential of 237 mV to attain a current density of 10 mA cm−2 and remarkable durability, with only a 3.3 % activity loss after 600 h at 100 mA cm−2 in alkaline seawater. Our findings present a viable strategy for repurposing spent LIBs into high‐performance catalysts for sustainable seawater electrolysis, contributing to the advancement of green hydrogen production technologies. [ABSTRACT FROM AUTHOR]

Developing cost‐effective, robust, and durable catalysts for water oxidation in acidic conditions remains a significant challenge for the practical application of proton exchange membrane electrolyzers. Cobalt‐based spinel catalysts, known for their effective oxygen evolution reaction (OER) activity in acidic environments, are promising alternatives to the costly iridium‐based catalysts. However, their application is often limited by poor stability under corrosive acidic conditions and oxidative potential. Here it is demonstrated that doping Co2MnO4 with Ni effectively regulates the structural and electronic properties of the catalysts, enabling stable operation for over 285 h at 100 mA cm−2 in 0.5 m H2SO4. This stability enhancement is primarily due to the increased exposure of the (400) facet, a result supported by theoretical studies. The proton exchange membrane water electrolysis (PEMWE) performance of Ni(5%)Co2MnO4 further demonstrates its potential, achieving 1 A cm−2 at a cell voltage of 2.3 V, with minimal degradation over 100 h at 500 mA cm−2. This study not only provides insights into the design of advanced OER catalysts through the doping of heteroatoms but also offers a pathway to enhance the sustainability and economic viability of acidic OER applications. [ABSTRACT FROM AUTHOR]

Anchoring groups play an important role in the assembly of functional molecules onto semiconductor substrates for dye‐sensitized photocatalysis. In addition to directly influencing the adsorption stability, anchoring groups significantly impact the efficiency of electron or hole injection into the substrate, which is a crucial step for photocatalytic reactions. Most reported dye‐sensitized photocatalytic systems, including semiconductor nanoparticles and photoelectrochemical cells, are prepared using the carboxylic or phosphonic acid anchors. The systems prepared with these conventional anchors usually suffer from low adsorption stability in aqueous media. Alternatively, pyridine has emerged as an anchoring group of photosensitizers and molecular catalysts in the construction of photocatalytic systems. The resulting semiconductor nanoparticles and photoelectrodes show superior adsorption stability in aqueous media, providing a simple and efficient way to sensitize the metal or metal oxide substrate. This review focuses on the recent advances of such a pyridine anchoring strategy in the assembly of photosensitizers and molecular catalysts for photocatalytic applications, mainly including photocatalytic water oxidation, reduction, and splitting. The further exploration and understanding of the pyridine‐anchoring method are believed to boost the development of advanced dye‐sensitized photocatalytic devices and technologies. [ABSTRACT FROM AUTHOR]

Electrocatalysts for the oxygen evolution process must be both active and stable in order to make hydrogen from water using renewable power. Nitrogen‐doped carbon layer coated cobalt manganate particles were synthesized on carbon cloth using calcination method. The catalysts exhibited small particle sizes and graphitized carbon layer that covered the cobalt manganate, facilitating electron flow. Moreover, the nitrogen‐doped carbon layer enhanced the oxygen evolution reaction (OER) rate by reducing the potential required for surface reconstruction and optimizing electron distribution on the cobalt manganate surface. This electrocatalyst demonstrated a current density of 100 mA/cm2 at 1.56 V vs. RHE. Thus, this electrocatalyst shows promise as a novel OER catalyst for water oxidation in acidic aqueous solutions. [ABSTRACT FROM AUTHOR]

Tristructural isotropic (TRISO) fuel particles, developed for use in high‐temperature gas‐cooled nuclear reactors, can be subjected to oxidizing environments in off‐normal accident scenarios. In this study, surrogate TRISO fuel particles were oxidized at 1000–1350°C for 4 h in 20 kPa water vapor atmosphere balanced with ultrahigh‐purity helium gas. The oxide scale morphology and thickness were studied via scanning electron microscopy, focused ion beam, and transmission electron microscopy. The oxide thickness increased as the oxidation temperature was increased. Although the oxide scale at 1000°C was completely amorphous, pockets of crystalline oxide were observed on particles oxidized at 1200 and 1300°C. Kinetic analysis was performed to deduce the oxidation mechanism by determining the apparent activation energy using linear regression analysis. The oxidation mechanism was consistent for temperatures from 1000 to 1200°C with an activation energy of 412.4 ± 8.8 kJ/mol. The activation energy then dropped to approximately 201 ± 7.1 kJ/mol for temperatures 1200–1350°C. Therefore, there is a change in oxidation mechanism at ∼1200°C. This change is attributed to the existence of a network of significant bubbles in the oxide layer at higher temperatures, which serve as rapid diffusion pathways for the transport of oxidants from the surface to the SiC/SiO2 interface, instead of relying on the bulk diffusion through the SiO2 layer at lower temperatures where only small bubbles are present along the SiC/SiO2 interface. [ABSTRACT FROM AUTHOR]

The synthesized RuO2/MnCo2O4.5 nano-heterostructure possesses dense interfaces and abundant defect structures, synergistically balancing oxygen evolution reaction (OER) activity and stability. RuO2/MnCo2O4.5 exhibits a low overpotential of 190 mV at 10 mA cm−2. The proton exchange membrane (PEM) electrolyzer assembled can operate at 200 mA cm−2 stably for 50 h. [ABSTRACT FROM AUTHOR]

Transition metal oxides (TMOs) are increasingly viable choices for catalytic applications because of their tendency to exhibit variable oxidation states depending on the chemical environment and the possibility of enhancing surface activity through morphology control. The development of efficient and cost-effective methods for the synthesis of TMOs with meso-to nanoscale morphologies and improved characteristics remains a significant challenge. Herein, we report a template-free synthesis strategy for the preparation of perforated mesoporous manganese(III) oxide microcubes (PMOM) through a morphology-conserved transformation of the precursor method. The formation of PMOM with cubic structures and pore sizes in the range of 20 nm was confirmed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Mn2O3 samples exhibited a Swiss cheese-like porous structure with a particle size of 0.70 to 1.2 μm. Furthermore, the catalytic activity of the synthesized PMOM samples on the thermocatalytic decomposition of ammonium perchlorate (AP), an oxidizer used in solid propellants, was investigated. The transition between Mn3+ to Mn2+ oxidation states facilitates the transfer of electrons, allowing the metal surface to act as an electron acceptor during the oxidation of water molecules. Due to the oxidation–reduction cycle occurring on the surface, a considerable number of electrons are available for promoting surface reactions. Thus, the (211) surface of PMOM enhanced the thermal decomposition of AP, and a plausible mechanism for this catalytic activity was proposed. [ABSTRACT FROM AUTHOR]

The construction of nanostructured heterostructure is a potent strategy for achieving high‐performance photoelectrochemical (PEC) water splitting. Among these, constructing BiVO4‐based heterostructure stands out as a promising method for optimizing light‐harvesting efficiency and reducing severe charge recombination. Herein, we present a novel approach to fabricate a type II heterostructure of core/shell Bi2S3/BiVO4 using electrolytic deposition and successive ionic layer adsorption and reaction (SILAR) methods. We identify the type II heterostructure and the difference in fermi energy using UV‐Vis spectroscopy, X‐ray photoelectron spectroscopy, and PEC measurements. This redistribution of charges due to the fermi energy difference induces an interfacial built‐in electric field from BiVO4 to Bi2S3, reinforcing the photogenerated hole transfer kinetics from BiVO4 to Bi2S3. The Bi2S3/BiVO4 heterostructure exhibits a superior photocurrent (6.0 mA cm−2), enhanced charge separation efficiency (85 %), and higher open‐circuit photovoltage (350 mV). Additionally, the heterostructure displays a prolonged average lifetime of charge (1.63 ns), verifying this heterojunction could boost interfacial carriers' migration via an additional nonradiative quenching pathway. Furthermore, the lower photoluminescence (PL) intensity demonstrates the interfacial built‐in electric field is beneficial for boosting charge migration. [ABSTRACT FROM AUTHOR]

Rapid cost reduction of green hydrogen is essential for the large‐scale deployment of hydrogen‐based energy system. A major component in achieving this is the development of advanced water electrolyzers. Sluggish oxygen evolution reaction (OER) is the bottleneck for water electrolysis, and tremendous efforts have been devoted to develop electrocatalysts that accelerate the OER kinetics. Recent advances have highlighted the potential of precious metal‐free OER electrocatalyst capable of stable operation at current densities above 1 A cm2. This brings an opportunity of constructing new‐generation electrolyzer with lower cost and higher productivity. However, achieving such high operating current densities presents new challenges. This review summarize the recent progress of high‐performance OER catalysts, and identifies key factors that can be leveraged to enhance catalyst activity. These factors include interface/surface engineering, amorphous and crystal phase coupling, hierarchical structure design, structural reconstruction and phase conversion, high entropy catalyst, and defect engineering. Additionally, the pressing challenges that have been largely ignored in previous research is addressed, such as sustaining long‐term stability under crucial conditions, disadvantages of immobilized powder electrocatalysts, electrode scale design, the necessity of designing innovative electrolyzer cell designs and advance characterization techniques. [ABSTRACT FROM AUTHOR]

Water oxidation, a crucial step in electrochemical water splitting, is often hindered by its complex kinetics. In our pursuit of designing efficient electrocatalysts, we have found that morphological modifications during synthesis are powerful tools. By manipulating various parameters, such as reaction time and temperature, we have tuned the morphology of the catalysts, leading to a significant enhancement in the oxygen evolution reaction (OER) rate. Our thorough research involves using a simple hydrothermal method for synthesizing bimetallic Ni–Cu oxides, resulting in the emergence of different morphologies by varying reaction times from 4 to 24 h. The OER performance in an alkaline medium, using a 1 M KOH solution, has been meticulously investigated, and our results have unveiled the highest activity for Ni–Cu fabricated with a growth time of 24 h. Ni–Cu oxide 24 exhibits a remarkably low onset potential for OER at 222 mV with a Tafel slope of 373 mV/dec. The catalyst boasts the lowest Rct value of 2.788 ohm, ensuring faster charge transfer rates and stability up to 1000 cyclic voltammetry (CV) cycles, thereby supporting its electrochemical applications for water splitting. [ABSTRACT FROM AUTHOR]

Faced with the dual challenges of energy shortage and environmental pollution, researchers are turning to extracting clean energy from waste resources. The coupled system of solar energy and supercritical water gasification offers a novel solution to these issues. In this study, a solar-driven supercritical water gasification-oxidation system for ammonia production and heat supply from chicken manure was simulated. Additionally, the effects of temperature of supercritical water gasification, chicken manure slurry concentration, water-dry matter ratio, and pressure of supercritical water gasification and oxidation on the system's products, efficiency, and device exergy losses were examined. Under typical working conditions (the temperature of supercritical water gasification: 750 °C, chicken manure slurry concentration: 50 wt%, water-dry matter ratio: 5, the pressure of supercritical water gasification and oxidation: 25 MPa), and the system had a treatment capacity of 5 t/h of dry chicken manure. The system yielded 2604.04 kg/h of NH 3 and 23763.9 kg/h of heating steam. It demonstrated an energy efficiency of 68.38% and an exergy efficiency of 46.85%. The total exergy losses of the system amounted to 34704.73kw, with the solar collector accounting for the largest share at 49.6%. The temperature of supercritical water gasification and water-dry matter ratio significantly impacted the system efficiency. Conversely, chicken manure slurry concentration and the pressure of supercritical water gasification and oxidation exerted minimal influence. The solar collector and gasification reactor emerged as the primary contributors to exergy losses in the entire system. Notably, the lower temperatures of supercritical water gasification, chicken manure slurry concentrations, pressures of supercritical water gasification and oxidation, and water-dry matter ratios can reduce exergy losses in both the solar collector and the gasification reactor. [Display omitted] • The supercritical water gasification and ammonia synthesis system were simulated. • The performance of system was analyzed by means of thermodynamic analysis. • The influence of operating parameters on the system is analyzed. • The energy efficiency and exergy efficiency reached 68.38% and 46.85% respectively. [ABSTRACT FROM AUTHOR]

Designing the strong interaction interface of oxygen precipitation co-catalyst with CdIn 2 S 4 is expected for efficient photoelectrochemical (PEC) water decomposition. Here, we develop a novel photoanode by constructing a NiOOH/CdIn 2 S 4 (NiOOH/CIS) heterogeneous interface and introducing F atoms to enhance the interface interaction. NiOOH/F:CdIn 2 S 4 (NiOOH/FCIS) exhibits excellent PEC activity with a high photocurrent density of 5.48 mA cm−2 at 1.23 V vs. RHE, and an outstanding incident photon-electron conversion efficiency (IPCE, 53.6% at 370 nm). It is found that doping of F atoms in CdInS 4 significantly reduces the bandgap of the photoanode, and more surprisingly, this impurity atom enhances the interfacial interactions between NiOOH and CIS, which greatly improves the hole-extraction ability of NiOOH. On this basis, an "impurity atom-assisted hole extraction" mechanism is proposed, the dopant atom can enhance the hole extraction ability of the co-catalyst by strengthening the heterogeneous interfacial interactions, thus improving the spatial separation efficiency of the photogenerated electrons and holes. An "impurity atom-assisted hole extraction" mechanism is proposed, the dopant atom can enhance the hole extraction ability of the co-catalyst by strengthening the heterogeneous interfacial interactions, thus improving the spatial separation efficiency of the photogenerated electrons and holes. [Display omitted] • Developed a novel photoanode NiOOH/F: CdIn 2 S 4 with strong interface effect. • NiOOH/F:CdIn 2 S 4 exhibits excellent PEC activity and outstanding IPEC efficiency. • F enhance hole extraction ability of NiOOH by improving interfacial interactions. • An "impurity atom-assisted hole extraction" mechanism is proposed. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting is regarded as a potential technique for converting solar energy. However, the fast charge recombination and slow water oxidation kinetics significantly have hindered its practical application. It is found that an elevation in operation temperature can activate the charge transport in the photoanodes. Here, a strategy was performed that carbon nanoparticles were employed to TiO2 nanorods, acting as electron reservoirs as well as photothermal materials. More specifically, a record photocurrent density of 1.62 mA cm−2 at 1.23 V vs. RHE has been achieved, accompanied by a high charge separation efficiency of 96% and a long-term durability for 8 h. The detailed experimental results reveal that under NIR light irradiation, the synergistic effect between electron storage and temperature rise leads to accelerated charge transport in the bulk and water oxidation kinetics on the surface. This research offers a new perspective on how to boost the PEC performance of photoelectrodes. [ABSTRACT FROM AUTHOR]

Water electro-oxidation to form H2O2 is an important way to produce H2O2 which is widely applied in industry. However, its mechanism is under debate and HO(ads), hydroxyl group adsorbed onto the surface of the electrode, is regarded as an important intermediate. Herein, we study the mechanism of water oxidation to H2O2 at Pt electrode using in-situ Raman spectroscopy and differential electrochemical mass spectroscopy and find peroxide bond mainly originated from the coupling of two CO32- via a C2O62- intermediate. By quantifying the 18O isotope in the product, we find that 93% of H2O2 was formed via the CO32- coupling route and 7% of H2O2 is from OH(ads)-CO3•− route. The OH(ads)-OH(ads) coupling route has a negligible contribution. The comparison of various electrodes shows that the strong adsorption of CO3(ads) at the electrode surface is essential. Combining with a commercial cathode catalyst to produce H2O2 during oxygen reduction, we assemble a flow cell in which the cathode and anode simultaneously produce H2O2. It shows a Faradaic efficiency of 150% of H2O2 at 1 A cm−2 with a cell voltage of 2.3 V. Electrosynthesis via two electron water reactions offers a promising method for decentralized H2O2 production, yet its mechanism remains unclear. Here, the authors address the challenge by using in-situ Raman and DEMS, and demonstrate 93% of H2O2 forms via the carbonate coupling route through a C2O62− intermediate. [ABSTRACT FROM AUTHOR]

Photosystem II (PSII) is a multi‐subunit protein‐pigment complex with diverse redox‐active cofactors, which enabled the biological availability of O2 on Earth. The substrate specificity and the underlying redox chemistry of the Mn4CaO5 catalytic center are investigated using alternate substrates such as small molecules (ammonia and methanol) and halides (Cl‐, Br‐, I‐) instead of the natural substrate water. Changes in the kinetic profiles of steady‐state O2 evolution and of dichlorophenolindophenol (DCIP) photochemical reduction by PSII as well as the detection of modified sites by proteomic analysis implied the possibility of alternate substrate photooxidation. Of particular interest is the role of two chlorides bound close to the putative water channels in the native system. The mutation of D2‐K317 to alanine is believed to impair the binding of a catalytically relevant chloride, eliminating the chloride requirement for water oxidation catalysis. The efficiency of small molecule photooxidation by the OEC is enhanced by the mutated D2‐K317A PSII complex without the competition from chloride. These results provide insight into the role of bound chloride in native PSII as a filter for enhancing the selectivity of water oxidation. The design principles for PSII may be extended to new strategies for developing highly selective catalysts. [ABSTRACT FROM AUTHOR]

FeNiOOH is regarded as the most stable active species in the oxygen evolution reaction (OER), but the high oxidation energy of NiOOH poses a challenge to directly synthesize FeNiOOH as a real OER catalyst. Herein, an anion‐mediated kinetically controlled strategy is proposed, coupled with cation‐induced geometric topology modulation, to directly synthesis FeNiOOH with ultra‐thin, densely packed nanosheet architectures. Specifically, the Cl−‐mediated in situ generation of hypochlorous acid promotes the direct formation of NiFeOOH. Concurrently, high‐valence competitive Ru3+ mitigate electrostatic repulsion, fostering a compact and densely packed assembly of Ru/FeNiOOH nanosheet branches. Furthermore, the intrinsic electron‐capturing ability of FeOOH, in synergy with the stabilizing effect of doped Ru atoms, further promote the formation and stabilization high‐valence NiOOH. Consequently, the hierarchical Ru/FeNiOOH@NiPOx nanoarray catalyst displays exceptional OER performance, with an overpotential of 172 mV at 10 mA cm−2 and outstanding stability. This study provides a novel strategy to directly construct a real catalyst. [ABSTRACT FROM AUTHOR]

The major hindrance to efficient electrocatalytic hydrogen generation from water electrolysis is the sluggish kinetics with corresponding large overvoltage of oxygen evolution reaction. Herein, we report a defective 2D NiCoMoS@Ni(CN) 2 core-shell heterostructure derived from Hofmann-type MOF as an efficient and durable high-performance noble metal-free electrocatalyst for hydrazine oxidation reaction (HzOR) in alkaline media. The sluggish oxygen evolution reaction was replaced with a more thermodynamically favourable HzOR, enabling energy-saving electrochemical hydrogen production with 2D NiCoMoS@Ni(CN) 2 acting as a bifunctional electrocatalyst for anodic HzOR and cathodic hydrogen generation. Operating at room temperature, the two-electrode electrolyzer delivers 100 mA cm−2 from a cell voltage of just 257 mV, with strong long-term electrochemical durability and nearly 100% Faradaic efficiency for hydrogen evolution in 1.0 M KOH aqueous solution with 0.5 M hydrazine. The density functional theory (DFT) was employed to investigate the origin of catalytic performance and showed that high vacancy creation within the heterointerface endowed NiCoMoS@Ni(CN) 2 with favourable functionalities for excellent catalytic performance. • A new approach of defect engineering in MOF-based nanocomposites is presented. • The synergistic interaction among different components promotes hydrazine-assisted water oxidation. • DFT was utilized to disentangle the active sites and mechanistic pathways for hydrogen production via hydrazine oxidation reaction. • The two electrode electrolyser proves superior to platinium/ruthenium oxide redox couple. [ABSTRACT FROM AUTHOR]

Boosting the reaction stability without sacrificing the activity and cost is extremely important but full of challenges for the RuO2‐based oxygen evolution catalysts. Herein, porous and B‐site substituted Y2[Mn0.2Ru0.8]2O7 (p‐Y2[Mn0.2Ru0.8]2O7) pyrochlore toward oxygen evolution reaction is innovatively synthesized. The formed meso‐/macroporous structure can increase the specific surface area and corresponding active sites, meanwhile, Mn‐substitution can modulate the electronic structure, stabilize the morphology, and reduce the dosage of Ru species. Interestingly, the p‐Y2[Mn0.2Ru0.8]2O7 performs 50 h stable operation, significantly outperforming the commercial RuO2(CM) counterpart with less than 2 h life. Furthermore, the required overpotential to achieve 10 mA cm−2 is only 266 mV, accompanied with favorable reaction kinetics and catalyst utilization. [ABSTRACT FROM AUTHOR]

NiFe oxyhydroxides, generally reconstructed on surface during oxygen evolution reaction (OER), are real active species for water oxidation; however, their direct and convenient preparation remains challenging. Here, we develop a one-step approach to prepare biphase (α/δ) Ni-doped FeOOH catalyst in 3 min under room temperature. The core of this ultrafast method is that Fe2+ derived from the redox reaction of Fe3+ and Ni2+ accelerate Fenton-like reaction, while simultaneously producing mixed-valence Ni ions(Ni2+, Ni3+) results in not only homovalent and heterovalent doping, but also biphase Ni-doped FeOOH heterojunction with high and low crystallinity. Specifically, Ni2+ doping leads to a preferred formation of low-crystalline δ-oriented Ni-doped FeOOH with abundant oxygen vacancies, which is in favor of triggering the lattice oxygen mechanism (LOM) during OER. Benefitting from high/low crystalline biphase heterojunction and LOM, the optimized Ni-FeOOH merely needs low overpotential of 300 mV to reach 1000 mA cm−2 for OER in alkaline electrolyte and also shows excellent durability even at a high current density of 500 mA cm−2. This work provides a cost-effective strategy to fabricate highly active and robust non-noble electrocatalysts that can potentially be applied for industrial-scale OER electrolysis. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting is pivotal for addressing the clean and renewable energy demands. However, developing low‐cost, efficient, and robust non‐precious metal catalysts for the acidic oxygen evolution reaction (OER) remains a significant challenge. In this study, we introduced Ce to modulate the electronic structure of Co3O4, enhancing the stability of Co3O4 without compromising its activity. Ce‐doped Co3O4 nanoparticles were electrodeposited onto Ti‐doped hematite surfaces (Ce : Co3O4/Fe2O3), significantly enhancing the PEC performance for water splitting under acidic conditions. These catalysts achieved high photocurrent densities and exhibited prolonged stability. Functioning as p‐type semiconductors, the Ce : Co3O4 nanoparticles not only boosted light absorption but also formed a p‐n heterojunction with the Ti‐doped hematite. This heterojunction generated a built‐in electric field that facilitated the separation and transfer of photogenerated carriers, thereby improving charge separation efficiency. Additionally, these nanoparticles expanded the active surface area of hematite and served as a co‐catalyst, markedly accelerating the OER kinetics. The Ce : Co3O4/Fe2O3 photoanode achieved an impressive photocurrent density of 1.08 mA cm−2 at 1.23 VRHE in acidic media, demonstrating its enhanced activity and stability. [ABSTRACT FROM AUTHOR]

The utilization of mild and environment-friendly reaction conditions for the photocatalytic oxidation of sulfides to highly valuable sulfoxides represents a sustainable approach that is highly desirable yet quite challenging. Herein, we present a novel approach to enhance the photocatalytic oxidation of sulfides in water by molecular structural engineering of donor–acceptor (D–A) based polymeric networks. By incorporating electron-deficient heptazine or triazine units as acceptors and electron-rich 2,5-diamino fluorene as donors, a synergistic effect is achieved, promoting efficient charge separation upon light absorption. The two polymeric networks namely HEP-FL and TZ-FL efficiently carried out selective oxidation of sulfides to sulfoxide with 100% conversion within 1.3 h and 3.5 h, respectively under blue light irradiation. Through advanced spectroscopic and electrochemical measurements, the correlation between molecular structures and optoelectronic properties is elucidated, unveiling tunable band structures and exciton binding energies. Notably, the heptazine-containing polymeric network (HEP-FL) exhibited superior charge separation efficiency and enhanced catalytic activity, attributed to improved electron delocalization and reduced exciton binding energy. Additionally, we have performed green metrics calculations for the synthesis of sulfoxide using HEP-FL as a photocatalyst to prove the sustainability of the reaction system. These findings underscore the significant prospects of donor–acceptor-based polymeric networks as highly effective photocatalysts for selective oxidation reactions, highlighting their potential to advance environmentally conscious practices in organic synthesis and industrial applications. [ABSTRACT FROM AUTHOR]

Tin(II) compounds are versatile materials with applications across fields such as catalysis, diagnostic imaging, and therapeutic drugs. However, oxidative stabilization of Sn(II) has remained an unresolved challenge as its reactivity with water and dioxygen results in loss of functionality, limiting technological advancement. Approaches to slow Sn(II) oxidation with chelating ligands or sacrificial electron donors have yielded only moderate improvements. We demonstrate here that the addition of nitrate to pyrophosphate-chelated Sn(II)(aq) suppresses Sn(II) oxidation in water across a broad pH range. Evidence of hydroxyl radical concentration reduction and detection of a radical nitrogen species that only forms in the presence of chelated Sn(II) point to a radical-based reaction mechanism. While this chemistry can be broadly applied, we present that this approach maintains Sn(II)'s antibacterial and anti-inflammatory efficacies as an example of sustained oral chemotherapeutic functionality. [ABSTRACT FROM AUTHOR]

Dual-shell reactors using hydrothermal flames as internal heat source were proposed for supercritical water gasification (SCWG) and oxidation (SCWO) of oily sludge to achieve fast preheating and avoid corrosion, salt plugging, and overheating. The SCWG and SCWO systems with hydrogen-rich syngas and electricity outputs, respectively, were established and simulated using Aspen Plus 11. Simulation models were validated by comparing with experimental products and temperature profiles. The maximum exergy destruction coefficients of 28.01% and 24.31% appear in the combustion reactor for both the SCWG and SCWO systems, respectively, indicating the indirect preheating method with hydrothermal flame is critical to the energy efficiency. The increase of reaction temperature promotes hydrogen but inhibits methane formation in the SCWG, and more steam but less syngas is output at higher reaction temperatures. Although more steam and electricity outputs are present at higher reaction temperatures for the SCWO, more fuel input is required. Lower exergy efficiencies are obtained at higher reaction temperatures in both the SCWG and SCWO systems for more energy is output as low grade steam. Less fuel input is required for both the SCWG and SCWO systems at higher feed concentrations, and higher exergy efficiencies can be obtained. The net treatment cost for the SCWG and SCWO systems are 119.19 and 215.47 USD/t, respectively, indicating the SCWG is more economically competitive compared with the SCWO. • Reactors with hydrothermal flames were proposed for SCWG and SCWO of oily sludge. • SCWG and SCWO systems with energy output were built and simulated by Aspen Plus. • The maximum exergy destruction appears in the combustion reactor for SCWG and SCWO. • Lower exergy efficiencies appear at higher temperatuers for more steam output. • The SCWG has certain economic superiority compared with the SCWO. [ABSTRACT FROM AUTHOR]

Hydrogen production technology by urea-assisted electrocatalytic water decomposition has become one of the important means to alleviate carbon emissions and water pollution. In this paper, we first doped Sn and Cu element into the Ni 3 S 2 material by hydrothermal method on the Ni foam support. This Cu–Sn–Ni 3 S 2 material exhibits superior urea (potential of 1.42 V at 100 mA cm−2) and water oxidation (potential of 1.63 V at 100 mA cm−2) properties, which is one of the best electrochemical performance reported up to now. Analysis of experiment demonstrate that the increase in catalytic performance is assigned to faster charge transfer, more exposure of reaction centres and smaller resistance owing to doping of Sn and Cu. Density functional theory (DFT) analysis demonstrates that introduction of Sn and Cu increases the adsorption energy of urea and improves the conductivity of the Cu–Sn–Ni 3 S 2 material, and the co-doping of the two changes the electron state density of the active site, thereby promoting the catalytic performance. This work provides insights into the development of efficient bifunctional electrodes for urea oxidation and oxygen evolution reaction through doping strategies. [Display omitted] • Cu and Sn ion co-doped Ni 3 S 2 nanoarrays were prepared by typical hydrothermal processes. • The Cu–Sn–Ni 3 S 2 presents an improved activity with small potentials of 1.63 V at 100 mA cm−2 for water oxidation. • The Cu–Sn–Ni 3 S 2 presents an improved activity with potentials of 1.42 V at 100 mA cm−2 for urea oxidation. [ABSTRACT FROM AUTHOR]

For the sluggish reaction kinetics due to a four‐electron transfer process, water oxidation is always a major obstacle to solar splitting of water to hydrogen. It remains a tough challenge to develop efficient nonnoble‐metal photocatalysts for water oxidation. Herein, we decorate the host photocatalyst of Bi11VO19 nanotubes with the coatalyst of subnanometer MoOx clusters (denoted as Bi11VO19/MoOx hetero‐nanotubes) via a one‐step cation‐exchange solvothermal reaction using Na2V6O16 nanowires as the hard template. It is observed that the morphology and microstructure of Bi11VO19/MoOx hetero‐nanotubes vary with the dosage of Mo source and polyvinylpyrrolidone, as well as with the solvent composition. The optimized Bi11VO19/MoOx hetero‐nanotubes significantly enhance the photooxidation of water to oxygen with visible light, delivering an oxygen production rate of 790 μmol g−1 h−1, which is 12 times that of bare Bi11VO19 nanotubes. In situ X‐ray photoelectron spectroscopy and (photo)electrochemical characterization suggest that the enhanced photoactivity may be caused by the decorated cocatalyst of MoOx clusters, which extracts electrons from Bi11VO19 nanotubes, leaving an abundance of holes for water photooxidation. This work demonstrates a potential strategy to develop photocatalysts for energy conversion by constructing Bi11VO19‐based nanostructures. [ABSTRACT FROM AUTHOR]

Water oxidation is a crucial reaction in the artificial photosynthesis system. In the present work, density functional calculations were employed to decipher the mechanism of water oxidation catalyzed by a binuclear cobalt complex, which was disclosed to be a homogeneous water oxidation catalyst in pH=7 phosphate buffer. The calculations showed that the catalytic cycle starts from the CoIII,III−OH2 species. Then, a proton‐coupled electron transfer followed by a one‐electron transfer process leads to the generation of the formal CoIV,IV−OH intermediate. The subsequent PCET produces the active species, namely the formal CoIV,V=O intermediate (4). The oxidation processes mainly occur on the ligand moiety, including the coordinated water moiety, implying a redox non‐innocent behavior. Two cobalt centers keep their oxidation states and provide one catalytic center for water activation during the oxidation process. 4 triggers the O−O bond formation via the water nucleophilic attack pathway, in which the phosphate buffer ion functions as the proton acceptor. The O−O bond formation is the rate‐limiting step with a calculated total barrier of 17.7 kcal/mol. The last electron oxidation process coupled with an intramolecular electron transfer results in the generation of O2. [ABSTRACT FROM AUTHOR]

This report describes a systematic approach for precise engineering of a catalyst‐metal oxide interface through combining complementary approaches of chemical vapor deposition and atomic layer deposition. Specifically, Chemical Vapor Deposition (CVD) fabricated nanostructured hard‐carbon framework (NCF) is employed as synergistic support for precise deposition of NiOx particles through Atomic Layer Deposition (ALD). The three variants of NCF‐NiOx system (dimensions ranging from 3–12 nm, surface coverage ranging from 0.14 %–2 %) achieved exhibit unique electrocatalytic water oxidation activities, that are further strongly influenced by an external magnetic field (Hext). This confluence of size engineering and associated magnetic field effects interplay to produce the largest lowering in Rct at Hext=200 mT. A comprehensive analysis of electrocatalytic parameters including the Tafel slope and double layer capacitance establishes further insights on co‐relation of size effect and magnetic properties to understand the role of nanocarbon supported transition metal oxides in water electrolysis. [ABSTRACT FROM AUTHOR]

The photoelectrochemical performance of Ta3N5 photoanodes is strongly impacted by the presence of shallow and deep defects within the bandgap. However, the role of such states in defining stability under operational conditions is not well understood. Here, a highly controllable synthesis approach is used to create homogenous Ta3N5 thin films with tailored defect concentrations to establish the relationship between atomic‐scale point defects and macroscale stability. Reduced oxygen contents increase long‐range structural order but lead to high concentrations of deep‐level states, while higher oxygen contents result in reduced structural order but beneficially passivate deep‐level defects. Despite the different defect properties, the synthesized photoelectrodes degrade similarly under water oxidation conditions due to the formation of a surface oxide layer that blocks interfacial hole injection and accelerates charge recombination. In contrast, under ferrocyanide oxidation conditions, it is found that Ta3N5 films with high oxygen concentrations exhibit long‐term stability, whereas those possessing lower oxygen contents and higher deep‐level defect concentrations rapidly degrade. These results indicate that deep‐level defects result in rapid trapping of photocarriers and surface oxidation but that shallow oxygen donors can be introduced into Ta3N5 to enable kinetic stabilization of the interface. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) activity on transition metal (TM) catalysts is governed by OER mechanism, yet discovering a controllable parameter to custom‐tailor OER mechanism remains a challenge. Here, the study highlights an eg electron‐filling state in octahedral TM‐catalysts, achieved by the modulation of splitting energy (Δ) via different anions (R) (Cl−, PO43−, NO3−, F−, SO42−, CO32−). The eg‐ electron filling state customization predominantly arises from the adjustment of Co‐dz2 orbital energy, which can tailor the bandgap between Co‐dz2 and O‐p orbits (Δεd‐p), thus customizing lattice‐oxygen (OL) activities and the OER mechanism. Combining the experimental measurements with DFT calculations, it is concluded that increased eg electron in TM‐catalysts brings decreased Δεd‐p, which can manageably strengthen lattice‐oxygen reactivity. Consequently, the OER mechanism on TM catalyst is transformed from adsorbate precipitation mechanism (AEM) to lattice oxygen oxidation mechanism (LOM) and customized OER pathways with different lattice‐oxygen activities. The screened PO43‐_TM, with the optimal OL activity in LOM path, possesses excellent activity and stability, achieving a current density of 10 mA cm−2 at 236 mV overpotential and maintaining stable operation for 300 h with inapparent degradation at 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting is a promising technology for green hydrogen production. However, severe charge recombination in the photoelectrode materials is one of the key obstacles to achieving high performance. Herein, a BiVO₄ photoanode with lattice strain (Str‐BVO) is constructed by generating Bi vacancies to promote charge separation in the bulk. The optimized Str‐BVO photoanode achieves a photocurrent density of 6.20 mA cm⁻2 at 1.23 V versus the reversible hydrogen electrode under AM 1.5 G illumination, with an impressive charge separation efficiency close to 100%. Systematical experiments and density functional theory reveal that the surface Bi vacancies induced strain causes the distortion of a small number of VO4 tetrahedra, which increases the antibonding state energy of most normal VO4 tetrahedra and creates more electronic vacancy states, thereby significantly promoting electron–hole separation. By surface loading with a FeNiOx co‐catalyst, the photoanode exhibits excellent PEC water‐splitting performance and stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • 13-year field test of a methane oxidising landfill cover with capillary barrier. • On average, the capillary barrier diverted 82% of the water reaching the barrier. • The diversion capacity decreased initially and recovered in the years after. • The cover soil optimised for CH 4 oxidation decreased capillary barrier performance. • Successful dual-functionality cover design must balance both components. This study quantifies the field hydraulic performance of a dual-functionality landfill cover, combining microbial methane oxidation with water diversion using a capillary barrier. The investigated 500 m2 test field, constructed on a landfill in the Netherlands, consisted of a cover soil optimised for methane oxidation, underlain by a sandy capillary layer and a gravelly capillary block. Outflows from these layers were measured between 2009 and 2023. Average precipitation was 848 mm/a, evapotranspiration, diverted infiltration and breakthrough amounted to 504 (59.4 %), 282 (33.3 %) and 62 (7.3 %) mm/a, respectively. On average, the capillary barrier diverted 82 % of the inflow into the capillary layer. Breakthrough occurred mainly from October to March when evapotranspiration was low and the maximum water storage capacity of the cover soil was reached. During this period, inflow into the capillary barrier exceeded its diversion capacity, caused by the relatively high hydraulic conductivity of the cover soil due to its optimisation for gas transport. The diversion capacity declined drastically in the year after construction and increased again afterwards. This was attributed to suffusion of sand from the capillary layer into the capillary block and subsequent washout to greater depths or the influence of iron precipitates at the bottom of the capillary layer. The effect of a more finely grained methane oxidation layer on the hydraulic and methane oxidation performance should be investigated further. These measures could further improve the combined performance of the dual functionality landfill cover system under the given conditions of a temperate climate. [ABSTRACT FROM AUTHOR]

SiCf/SiC composites are replacing superalloy components in hot sections of gas turbines. The high-velocity combustion gases in gas turbine hot sections contain water vapor. The mechanism of oxidative water vapor attack on SiC is vastly different from that of oxidation in static dry air. Therefore, it is of paramount importance to study the oxidation of these composites in high-velocity combustion environments. This study focuses on the high-temperature oxidation behavior of SiCf/SiC composites with a BN interfacial coating in both static air and combustion environments. The composite was prepared by the chemical vapor infiltration process (CVI). To elucidate the impact of water vapor in a combustion environment, an oxyacetylene flame apparatus was used. Oxidation of the SiCf/SiC composite was investigated at 1200, 1300 and 1400 °C, for up to 100 h in static dry air, and for up to 24 h in a combustion environment. The microstructure evolution and recession of the composite under combustion environment were investigated by scanning electron microscopy. The oxidation kinetics of the SiCf/SiC composite showed a parabolic nature in static air; however, in the combustion environment the composite showed accelerated mass loss owing to the concurrent effects of oxidation and recession. [ABSTRACT FROM AUTHOR]

Developing an advanced strategy to decrease the charge recombination of BiVO4 is a vital requirement to boost charge transfer for photoelectrochemical water oxidation. Herein, a type II BiVO4/Bi2Mo2O9 heterojunction is successfully synthesized on fluorine‐doped tin oxide substrate by successive ionic layer adsorption and reaction method. Thanks to the Fermi‐level energy difference of 275 mV between BiVO4 and Bi2Mo2O9, an outward built‐in electric filed pointing from Bi2Mo2O9 to BiVO4 is induced, which accelerates the directional flowing of photogenerated electron and hole. Such a unique design structure fastens the electron migration from BiVO4 to Bi2Mo2O9, and the holes will transfer to the surface to participate in water oxidation. The longer lifetime (9.2 ns) by time‐resolved transient photoluminescence signifies that the Bi2Mo2O9 can boost interfacial carriers' anisotropic migration; the surface charge transfer rate of BiVO4/Bi2Mo2O9 is up to 387.6 s−1 (1.4 V vs reversible hydrogen electrode (RHE)). The BiVO4/Bi2Mo2O9 heterojunction exhibits a remarkable charge separation efficiency of 64% and outstanding photocurrent density of 0.9 mA cm−2 at 1.23 V versus RHE. [ABSTRACT FROM AUTHOR]

Photocatalyst‐assisted charge transfer at the interface between two immiscible electrolyte solutions (ITIES) has been previously proven. However, its practical application requires information on its performance under solar irradiation. We investigated photocatalyst‐assisted oxidation of water at ITIES under solar irradiation using TCNQ 7,7,8,8‐Tetracyanoquinodimethane (TCNQ) as electron scavenger and bis(triphenylphosphoranylidene) ammonium tetrakis(4‐chlorophenyl)borate (BTPPA‐TPBCl) as organic phase electrolyte. No enhancement of water oxidation after assembling photocatalyst nanoparticles at the ITIES was observed. Photocurrents with photocatalyst were similar to those without but in the presence of TCNQ. Photocurrents observed both with and without photocatalyst are shown to be due to photogeneration of TCNQ⋅−, either by reaction with the organic electrolyte or by interfacial oxidation of water. The former dominates at positive potentials and results in a positive photocurrent due to transfer of TCNQ⋅− across the ITIES. The latter dominates at negative potentials and results in a negative photocurrent. Electron paramagnetic resonance (EPR) detected TCNQ⋅− and revealed its stabilisation by formation of an adduct with BTPPA+, which must contribute to making the photoactivity of TCNQ the dominant process even with photocatalyst. These findings highlight the necessity of research on alternative suitable electron scavenger‐supporting electrolyte combinations for implementing ITIES in the photoelectrocatalytic conversion of solar energy. [ABSTRACT FROM AUTHOR]

Electricity-driven water splitting to produce hydrogen is one of the most efficient ways to alleviate energy crisis and environmental pollution problems, in which the anodic oxygen evolution reaction (OER) is the key half-reaction of performance-limiting in water splitting. Given the complicated reaction process and surface reconstruction of the involved catalysts under actual working conditions, unraveling the real active sites, probing multiple reaction intermediates and clarifying catalytic pathways through in-situ characterization techniques and theoretical calculations are essential. In this review, we summarize the recent advancements in understanding the catalytic process, unlocking the water oxidation active phase and elucidating catalytic mechanism of water oxidation by various in-situ characterization techniques. Firstly, we introduce conventionally proposed traditional catalytic mechanisms and novel evolutionary mechanisms of OER, and highlight the significance of optimal catalytic pathways and intrinsic stability. Next, we provide a comprehensive overview of the fundamental working principles, different detection modes, applicable scenarios, and limitations associated with the in-situ characterization techniques. Further, we exemplified the in-situ studies and discussed phase transition detection, visualization of speciation evolution, electronic structure tracking, observation of reaction active intermediates, and monitoring of catalytic products, as well as establishing catalytic structure--activity relationships and catalytic mechanism. Finally, the key challenges and future perspectives for demystifying the water oxidation process are briefly proposed. [ABSTRACT FROM AUTHOR]

AbstractCopper carbonate/bicarbonate complexes are good catalysts of the oxygen evolution reaction, OER. Previous electro-catalytic studies suggested that at pH 10.8 the active intermediate is a CuIII complex whereas at pH 6.8 the active intermediate is a CuIV complex. Previous pulse-radiolysis studies indicated that CuIII complexes are the active intermediates at both pHs. To solve the source of this discrepancy, the copper carbonate/bicarbonate catalyzed OER using peroxy-mono-sulfate as the oxidant was studied. In this system CuIV complexes are the active intermediates. The result points out that two electron oxidants yield CuIV complexes and one electron oxidants yield CuIII complexes; both types of complexes are water oxidation agents. Electrochemical processes might proceed via both mechanisms as the anode can act as a two-electron acceptor. Thus, pulse-radiolysis does not always yield the same intermediates as electrochemistry. [ABSTRACT FROM AUTHOR]

BiVO4 is one of the most promising candidates for photoelectrochemical water oxidation. However, the poor crystallinity and short hole diffusion length limit its charge separation. One bottleneck stems from the contradiction between high crystallinity and small particles via conventional furnace heating processes. This paper describes the design and fabrication of BiVO4 photoanodes via rapid thermal process (RTP), rather than furnace heating, to decouple the constraints between nucleation, crystallization, and growth processes of BiVO4. The higher heating ramp rate of RTP compared with furnace heating promotes the fast diffusion of reactant molecules, which elevates the nucleation rate above the particle growth rate of BiVO4, leading to small particles with high crystallinity. Moreover, the ultra‐high heating temperature makes it possible to crystallize the small BiVO4 particle within a short time. Thus, a high crystallinity can be obtained for the RTP‐treated BiVO4 while maintaining small particle size, achieving a charge separation efficiency of up to 82%, 30% higher than that of furnace‐treated BiVO4 photoanode. [ABSTRACT FROM AUTHOR]

Natural photosynthesis enzymes utilize energies of several photons for challenging oxidation of water, whereas artificial photo‐catalysis typically involves only single‐photon excitation. Herein, a multiphoton excitation strategy is reported that combines parallel photo‐excitations with a photoinduced electron transfer process for the activation of C(sp3)─H bonds, including methane. The metal–organic framework Fe3‐MOF is designed to consolidate 4,4′,4″‐nitrilotrisbenzoic units for the photoactivation of dioxygen and trinuclear iron clusters as the HAT precursor for photoactivating alkanes. Under visible light irradiation, the dyes and iron clusters absorbed parallel photons simultaneously to reach their excited states, respectively, generating 1O2 via energy transfer and chlorine radical via ligand‐to‐metal charge transfer. The further excitation of organic dyes leads to the reduction of 1O2 into O2•− through a photoinduced electron transfer, guaranteeing an extra multiphoton oxygen activation manner. The chlorine radical abstracts a hydrogen atom from alkanes, generating the carbon radical for further oxidation transformation. Accordingly, the total oxidation conversion of alkane utilizing three photoexcitation processes combines the energies of more than two photons. This new platform synergistically combines a consecutive excited photoredox organic dye and a HAT catalyst to combine the energies of more than two photons, providing a promising multiphoton catalysis strategy under energy saving, and high efficiency. [ABSTRACT FROM AUTHOR]

The innovative development of reactive‐spray systems for gas‐phase production of metal sulfides are potential materials for next‐generation technologies. These flame‐synthesized sulfides (doped, functionalized, and heterogeneously mixed derivatives) hold significant potential as photocatalysts for water splitting. The knowledge acquired from nonaqueous precursor‐solvent and high‐temperature aerosol chemistries, optimal process parameters are established to generate In2‐(4/3)xSnxS3, solid‐solutions. The thermally driven reducing gas‐phase reactions are controlled through fuel/oxygen ratio. Particles characterizations (X‐ray diffraction, transmission electron microscopy (TEM) and imaging) revealed structural stability and crystallinity. The In2‐(4/3)xSnxS3, at higher Sn doping had enhanced photoexcitation. Donor‐acceptor levels within the material facilitated electron‐hole pair trapping, crucial for redox reactions. With suitable band gap energies for water oxidation (1.91.1 eV) closely matched flat band potentials (4.384.67 eV) for redox reactions. The powder characterization showed 8% In2O3 in InSn0.75S3 after photocatalysis due to S‐degradation in the initial light “on/off cycles”. The pioneering process of employing oxygen‐deficient reducing flame enabled a series of photo‐catalytically active metal sulfide nanoparticles with work function energies in the range of 5.195.37 eV. This synthesis strategy holds the potential for impactful advancements in both industry and R&D, addressing the urgent need for new materials capable of inducing water oxidation under visible light. [ABSTRACT FROM AUTHOR]

BiVO4 is an attractive photoanode material for water oxidation, but requires surface treatment to improve the energy efficiency and stability. Herein, we investigate the role of borate buffer in activating the BiVO4 photoanode. We found that trace iron impurities in the borate buffer play a critical role in activating the photoanode. By optimizing the activation conditions, the photocurrent density attains 4.5 mA cm−2 at 1.23 VRHE without any cocatalysts, alongside a high ABPE value of 1.5% at 0.7 VRHE. Our study discloses the role of iron in the activation effect of borate buffer on the BiVO4 photoanode, which has implications for other catalytic systems. [ABSTRACT FROM AUTHOR]

The electroconversion of carbon dioxide (CO2) into value-added chemicals has attracted widespread attention worldwide. Exploring efficient catalysts and designing reasonable reactants have become popular research directions in the strategy of coupling anode and cathode reactions. Herein, we report the construction of a self-supporting bifunctional Sn-SnSx electrode using a one-step electrodeposition method. The valence states of Sn at the Sn-SnSx surface are Sn4+, Sn2+ and Sn0, and the electrode exhibits excellent performances for the carbon dioxide reduction reaction (CO2RR) and glucose oxidation reaction (GOR), respectively. For the CO2RR, the Sn-SnSx electrode produced formate with a faradaic efficiency (FE) of 93.3% and a stability of 36 h. Meanwhile, tin sulfides were first applied in anodic oxidation and a high FE of 88% was achieved for formate production in the GOR. Impressively, Sn-SnSx as a bifunctional electrode achieved co-production of formate at both the anode and cathode in the integrated electrolyzer coupled with the CO2RR and GOR. This coupling process combines the technical means of "electrooxidation-electroreduction" with the choice of reactants "CO2-C6H12O6", resulting in FE values of 93.9% and 87.4% at the cathode and anode for the production of formate, as well as a 58.3% electrical energy saving for formate production in comparison with the traditional CO2RR coupled with the water oxidation reaction. [ABSTRACT FROM AUTHOR]

Exploring Earth-abundant and efficient electrocatalysts to replace Ir and Ru for the acidic oxygen evolution reaction (OER) is essential to reduce the cost of clean hydrogen production. Here, we show that trace amounts of electronegative non-metallic element fluorine (F)-doped Co3O4 nanoneedles improve the activity and stability of Co3O4. The F-doped Co3O4 nanoneedles supported on carbon paper (F-Co3O4/CP) exhibit an overpotential of 350 mV at 10 mA cm-2 for the acidic OER. In addition, their performance remains consistent after continuous operation for 80 h. Detailed investigations reveal that introducing an anion promotes the enrichment of OH on the surface of Co3O4 and prevents acid corrosion, thereby enhancing the intrinsic OER activity and stability. Theoretical calculations further indicate that F doping can effectively improve electron transfer and optimize the energy barrier for the formation of *OOH intermediates, which significantly improves OER performance. This study provides guidance for designing efficient and stable non-noble metal acidic water oxidation catalysts. [ABSTRACT FROM AUTHOR]