Metal–Organic Framework Derived Narrow Bandgap Cobalt Carbide Sensitized Titanium Dioxide Nanocage for Superior Photo‐Electrochemical Water Oxidation Performance

Despite recent progress in photo‐electrochemical (PEC) water oxidation systems for TiO₂‐based photoanodes, PEC performance improvement is still seriously hampered due to poor carrier transport efficiency and sluggish surface water oxidation kinetics of pristine TiO₂. Herein, for the first time a brand new metal–organic framework (MOF)‐derived Co₃C nanosheet with narrow bandgap energy is demonstrated, to effectively sensitize TiO₂ hollow cages as a heterostructure photoanode for PEC water oxidation. It is found that MOF‐derived Co₃C nanosheet with narrow bandgap characteristic can simultaneously accelerate the surface water oxidation kinetics and extend the light harvesting range of pristine TiO₂. Meanwhile, a uniquely matched type‐II heterojunction constructed between MOF‐derived Co₃C and TiO₂ results in an evidently spontaneous e^?/h⁺ separation. MOF‐derived Co₃C/TiO₂ heterostructure photoanodes bring about drastically improved PEC water oxidation performance. Specifically, MOF‐derived Co₃C‐3/TiO₂ photoanode with an optimized content of Co₃C achieves the highest photocurrent density and charge separation efficiency of 2.6 mA cm^?2 and 92.6% at 1.23 V versus reversible hydrogen electrode, corresponding to 201% and 152% improvement compared with pristine TiO₂ nanocages. The ingeniously prepared MOF‐derived Co₃C carbide with narrow bandgap energy as a cocatalyst paves new way to construct potentially high performance solar‐energy conversion system.     

New Iron‐Cobalt Oxide Catalysts Promoting BiVO4 Films for Photoelectrochemical Water Splitting

Owing to the sluggish kinetics for water oxidation, severe surface charge recombination is a major energy loss that hinders efficient photoelectrochemical (PEC) water splitting. Herein, a simple process is developed for preparing a new type of low‐cost iron‐cobalt oxide (FeCoO_x) as an efficient co‐catalyst to suppress the surface charge recombination on bismuth vanadate (BiVO₄) photoanodes. The new FeCoO_x/BiVO₄ photoanode exhibits a high photocurrent density of 4.82 mA cm^?2 at 1.23 V versus the reversible hydrogen electrode under AM 1.5 G illumination, which corresponds to >100% increase compared to that of the pristine BiVO₄ photoanode. The photoanode also demonstrates a high charge separation efficiency of ≈90% with excellent stability of over 10 h, indicating the excellent catalytic performance of FeCoO_x in the PEC process. Density functional theory calculations and experimental studies reveal that the incorporation of Fe into CoO_x generates abundant oxygen vacancies and forms a p‐n heterojunction with BiVO₄, which effectively promotes the hole transport/trapping from the BiVO₄ photocatalyst and reduces the overpotential for oxygen evolution reaction (OER), resulting in remarkably increased photocurrent densities and durability. This work demonstrates a feasible process for depositing cheap FeCoO_x as an excellent OER cocatalyst on photoanodes for PEC water splitting.     

Amorphous Cobalt–Iron Hydroxide Nanosheet Electrocatalyst for Efficient Electrochemical and Photo‐Electrochemical Oxygen Evolution

Finding efficient electrocatalysts for oxygen evolution reaction (OER) that can be effectively integrated with semiconductors is significantly challenging for solar‐driven photo‐electrochemical (PEC) water splitting. Herein, amorphous cobalt–iron hydroxide (CoFe? H) nanosheets are synthesized by facile electrodeposition as an efficient catalyst for both electrochemical and PEC water oxidation. As a result of the high electrochemically active surface area and the amorphous nature, the optimized amorphous CoFe? H nanosheets exhibit superior OER catalytic activity in alkaline environment with a small overpotential (280 mV) to achieve significant oxygen evolution (j = 10 mA cm^?2) and a low Tafel slope (28 mV dec^?1). Furthermore, CoFe? H nanosheets are simply integrated with BiVO₄ semiconductor to construct CoFe? H/BiVO₄ photoanodes that exhibit a significantly enhanced photocurrent density of 2.48 mA cm^?2 (at 1.23 V vs reversible hydrogen electrode (RHE)) and a much lower onset potential of 0.23 V (vs RHE) for PEC‐OER. Careful electrochemical and optical studies reveal that the improved OER kinetics and high‐quality interface at the CoFe? H/BiVO₄ junction, as well as the excellent optical transparency of CoFe? H nanosheets, contribute to the high PEC performance. This study establishes amorphous CoFe? H nanosheets as a highly competitive candidate for electrochemical and PEC water oxidation and provides general guidelines for designing efficient PEC systems.     

Aging of a Vanadium Precursor Solution: Influencing Material Properties and Photoelectrochemical Water Oxidation Performance of Solution‐Processed BiVO4 Photoanodes

Metal–organic decomposition is an easy way to fabricate BiVO₄ (BVO) photoanodes; however, it often experiences a reproducibility issue. Here, the aging duration of a vanadium precursor solution, vanadyl acetylacetonate in methanol, is identified as a factor that profoundly affects reproducibility. Substantial changes in structural, optical, and electrical properties of BVO films are observed upon varying aging time of vanadium precursor solutions, which subsequently impacts photoelectrochemical (PEC) water oxidation and sulfite oxidation reactions. With the optimum number of aging days (3 d), some deficiency of oxygen is observed, which is accompanied by an increase in carrier concentration and a reduced charge transfer resistance in the PEC device, which produces the highest PEC performance that is comparable to the state‐of‐the‐art undoped BVO photoanodes. The findings point to the importance of understanding solution chemistry and demonstrate that utilization of the understanding of fine adjustment of the composition of BVO films can produce highly reproducible and efficient BiVO₄ photoanodes.     

Photoinduced Magnetization with a High Curie Temperature and a Large Coercive Field in a Co‐W Bimetallic Assembly

The crystal structure, magnetic properties, and temperature‐ and photoinduced phase transition of [{Co^II(4‐methylpyridine)(pyrimidine)}₂{Co^II(H₂O)₂}{W^V(CN)₈}₂]·4H₂O are described. In this compound, a temperature‐induced phase transition from the Co^II (S = 3/2)‐NC‐W^V(S = 1/2) [high‐temperature (HT)] phase to the Co^III(S = 0)‐NC‐W^IV(S = 0) [low temperature (LT)] phase is observed due to a charge‐transfer‐induced spin transition. When the LT phase is irradiated with 785 nm light, ferromagnetism with a high Curie temperature (T_C) of 48 K and a gigantic magnetic coercive field (H_c) of 27 000 Oe are observed. These T_C and H_c values are the highest in photoinduced magnetization systems. The LT phase is optically converted to the photoinduced phase, which has a similar valence state as the HT phase due to the optically induced charge‐transfer‐induced spin transition.     

Highly Efficient Photoelectrochemical Water Splitting: Surface Modification of Cobalt‐Phosphate‐Loaded Co3O4/Fe2O3 p–n Heterojunction Nanorod Arrays

Hematite (α‐Fe₂O₃) as a photoanode material for photoelectrochemical (PEC) water splitting suffers from the two problems of poor charge separation and slow water oxidation kinetics. The construction of p–n junction nanostructures by coupling of highly stable Co₃O₄ in aqueous alkaline environment to Fe₂O₃ nanorod arrays with delicate energy band positions may be a challenging strategy for efficient PEC water oxidation. It is demonstrated that the designed p‐Co₃O₄/n‐Fe₂O₃ junction exhibits superior photocurrent density, fast water oxidation kinetics, and remarkable charge injection and bulk separation efficiency (η_inj and η_sep), attributing to the high catalytic behavior of Co₃O₄ for the oxygen evolution reaction as well as the induced interfacial electric field that facilitates separation and transportation of charge carriers. In addition, a cocatalyst of cobalt phosphate (Co‐Pi) is introduced, which brings the PEC performance to a high level. The resultant Co‐Pi/Co₃O₄/Ti:Fe₂O₃ photoanode shows a photocurrent density of 2.7 mA cm^?2 at 1.23 V_RHE (V vs reversible hydrogen electrode), 125% higher than that of the Ti:Fe₂O₃ photoanode. The optimized η_inj and η_sep of 91.6 and 23.0% at 1.23 V_RHE are achieved on Co‐Pi/Co₃O₄/Ti:Fe₂O₃, respectively, corresponding to the 70 and 43% improvements compared with those of Ti:Fe₂O₃. Furthermore, Co‐Pi/Co₃O₄/Ti:Fe₂O₃ shows a low onset potential of 0.64 V_RHE and long‐time PEC stability.     

Modulating Carrier Kinetics in BiVO4 Photoanodes through Molecular Co4O4 Cubane Layers

Understanding the role and immobilization of molecular catalysts on photoelectrodes is essential to use their full potential for efficient solar fuel generation. Here, a Co^II₄O₄ cubane with proven catalytic performance and an active H₂O─Co₂(OR)₂─OH₂ edge-site moiety is immobilized on BiVO₄ photoanodes through a versatile layer-by-layer assembly strategy. This delivers a photocurrent of 3.3 mA cm⁻² at 1.23 V_RHE and prolonged stability. Tuning the thickness of the Co₄O₄ layer has remarkable effects on photocurrents, dynamic open circuit potentials, and charge carrier behavior. Comprehensive-time and frequency-dependent perturbation techniques are employed to investigate carrier kinetics in transient and pseudo-steady-state operando conditions. It is revealed that the Co₄O₄ layer can prolong carrier lifetime, unblock kinetic limitations at the interface by suppressing recombination, and enhance charge transfer. Additionally, its flexible roles are identified as passivation/hole trapping/catalytic layer at respective lower/moderate/higher potentials. These competing functions are under dynamic equilibrium, which fundamentally defines the observed photocurrent trends.     

Modular Layer‐by‐Layer Assembly of Polyelectrolytes,Nanoparticles, and Molecular Catalysts into Solar‐to‐Chemical Energy Conversion Devices

The design and fabrication of solar‐to‐chemical energy conversion devices are enabled through interweaving multiple components with various morphologies and unique functions using a versatile layer‐by‐layer assembly method. Cationic and anionic polyelectrolytes are used as an electrostatic adhesive to assemble the following functional materials: plasmonic Ag nanoparticles for improved light harvesting, upconversion nanoparticles for utilization of near‐infrared light, and polyoxometalate water oxidation catalysts for enhanced catalytic activity. Polyelectrolytes also have an additional function of passivating the surface recombination centers of the underlying photoelectrode. These functional components are precisely assembled on a model photoanode (e.g., Fe₂O₃ and BiVO₄) in a desired order and various combinations without degradation of their intrinsic properties. As a result, the performance of water oxidation photoanodes is synergistically enhanced. This study can enable the design and fabrication of novel solar‐to‐chemical energy conversion devices.     

Metal–Organic Framework Derived Co3O4/TiO2/Si Heterostructured Nanorod Array Photoanodes for Efficient Photoelectrochemical Water Oxidation

A novel hierarchical structured photoanode based on metal–organic frameworks (MOFs)‐derived porous Co₃O₄‐modified TiO₂ nanorod array grown on Si (MOFs‐derived Co₃O₄/TiO₂/Si) is developed as photoanode for efficiently photoelectrochemical (PEC) water oxidation. The ternary Co₃O₄/TiO₂/Si heterojunction displays enhanced carrier separation performance and electron injection efficiency. In the ternary system, an abnormal type‐II heterojunction between TiO₂ and Si is introduced, because the conduction band and valence band position of Si are higher than those of TiO₂, the photogenerated electrons from TiO₂ will rapidly recombine with the photogenerated holes from Si, thus leading to an efficient separation of photogenerated electrons from Si/holes from TiO₂ at the TiO₂/Si interface, greatly improving the separation efficiency of photogenerated hole within TiO₂ and enhances the photogenerated electron injection efficiency in Si. While the MOFs‐derived Co₃O₄ obviously improves the optical‐response performance and surface water oxidation kinetics due to the large specific surface area and porous channel structure. Compared with MOFs‐derived Co₃O₄/TiO₂/FTO photoanode, the synergistic function in the MOFs‐derived Co₃O₄/TiO₂/Si NR photoanode brings greatly enhanced photoconversion efficiency of 0.54% (1.04 V vs reversible hydrogen electrode) and photocurrent density of 2.71 mA cm^?2 in alkaline electrolyte. This work provides promising methods for constructing high‐performance PEC water splitting photoanode based on MOFs‐derived materials.     

Zinc Ferrite Photoanode Nanomorphologies with Favorable Kinetics for Water‐Splitting

The n‐type semiconducting spinel zinc ferrite (ZnFe₂O₄) is used as a photoabsorber material for light‐driven water‐splitting. It is prepared for the first time by atomic layer deposition. Using the resulting well‐defined thin films as a model system, the performance of ZnFe₂O₄ in photoelectrochemical water oxidation is characterized. Compared to benchmark α‐Fe₂O₃ (hematite) films, ZnFe₂O₄ thin films achieve a lower photocurrent at the reversible potential. However, the oxidation onset potential of ZnFe₂O₄ is 200 mV more cathodic, allowing the water‐splitting reaction to proceed at a lower external bias and resulting in a maximum applied‐bias power efficiency (ABPE) similar to that of Fe₂O₃. The kinetics of the water oxidation reaction are examined by intensity‐modulated photocurrent spectroscopy. The data indicate a considerably higher charge transfer efficiency of ZnFe₂O₄ at potentials between 0.8 and 1.3 V versus the reversible hydrogen electrode, attributable to significantly slower surface charge recombination. Finally, nanostructured ZnFe₂O₄ photoanodes employing a macroporous antimony‐doped tin oxide current collector reach a five times higher photocurrent than the flat films. The maximum ABPE of these host–guest photoanodes is similarly increased.     

High‐Performing Monometallic Cobalt Layered Double Hydroxide Supercapacitor with Defined Local Structure

Through a topochemical oxidative reaction (TOR) under air, a β‐Co(OH)₂ brucite type structure is converted into a monometallic Co^IICo^III–CO₃ layered double hydroxide (LDH). The structural and morphological characterizations are performed using powder X‐ray diffraction, Fourier‐transformed IR spectroscopy, and scanning and transmission electron microscopy. The local structure is scrutinized using an extended X‐ray absorption fine structure, X‐ray absorption near‐edge structure, and pair distribution function analysis. The chemical composition of pristine material and its derivatives (electrochemically treated) are identified by thermogravimetry analysis for the bulk and X‐ray photoelectron spectroscopy for the surface. The electrochemical behavior is investigated on deposited thin films in aqueous electrolyte (KOH) by cyclic voltammetry and electrochemical impedance spectroscopy, and their capacitive properties are further investigated by Galvanostatic cycling with potential limitation. The charge capacity is found to be as high as 1490 F g^?1 for Co^IICo^III–CO₃ LDH at a current density of 0.5 A g^?1. The performances of these materials are described using Ragone plots, which finally allow us to propose them as promising supercapacitor materials. A surface‐to‐bulk comparison using the above characterization techniques gives insight into the cyclability and reversibility limits of this material.     

Improvement of BiVO4 Photoanode Performance During Water Photo‐Oxidation Using Rh‐Doped SrTiO3 Perovskite as a Co‐Catalyst

In this work, a water splitting photoanode composed of a BiVO₄ thin film surface modified by the deposition of a rhodium (Rh)‐doped SrTiO₃ perovskite is fabricated, and the Rh‐doped SrTiO₃ outer layer exhibits special photoelectrochemical (PEC) oxygen evolution co‐catalytic activity. Controlled intensity modulated photo‐current spectroscopy, electrochemical impedance spectroscopy, and other electrochemical results indicate that the Rh on the perovskite provide an oxidation active site during the PEC water oxidation process by reducing the reaction energy barrier for water oxidation. Theoretical calculations indicate that the water oxidation reaction is more likely to occur on the (110) crystal plane of Rh‐SrTiO₃ because the oxygen evolution reaction overpotential on the (110) crystal plane is reduced significantly. Therefore, the obtained BiVO₄/Rh5%‐SrTiO₃ photoanode exhibits an optimized PEC performance. In particular, it facilitates the saturation of the photocurrent density. Thus, the presence of doped Rh in SrTiO₃ can reduce the amount of noble metals required while achieving excellent and stable oxygen evolution properties.     

Improved Photocatalytic Performance of Heterojunction by Controlling the Contact Facet: High Electron Transfer Capacity between TiO2 and the {110} Facet of BiVO4 Caused by Suitable Energy Band Alignment

Charge separation at the interface of heterojunctions is affected by the energy band alignments of the materials that compose the heterojunctions. Controlling the contact crystal facets can lead to different energy band alignments owing to the varied electronic structures of the different crystal facets. Therefore, BiVO₄‐TiO₂ heterojunctions are designed with different BiVO₄ crystal facets at the interface ({110} facet or {010} facet), named BiVO₄‐110‐TiO₂ and BiVO₄‐010‐TiO₂, respectively, to achieve high photocatalytic performance. Higher photocurrent density and lower photoluminescence intensity are observed with the BiVO₄‐110‐TiO₂ heterojunction than those of the BiVO₄‐010‐TiO₂ heterojunction, which confirms that the former possesses higher charge carrier separation capacity than the latter. The photocatalytic degradation results of both Rhodamine B and 4‐nonylphenol demonstrate that better photocatalytic performance is achieved on the BiVO₄‐110‐TiO₂ heterojunction than the BiVO₄‐010‐TiO₂ heterojunction under visible light (≥422 nm) irradiation. The higher electron transfer capacity and better photocatalytic performance of the BiVO₄‐110‐TiO₂ heterojunction are attributed to the more fluent electron transfer from the {110} facet of BiVO₄ to TiO₂ caused by the smaller interfacial energy barrier. This is further confirmed by the selective deposition of Pt on the TiO₂ surface as well as the longer lifetime of Bi⁵⁺ in the BiVO₄‐110‐TiO₂ heterojunction.     

Hematite Films Decorated with Nanostructured Ferric Oxyhydroxide as Photoanodes for Efficient and Stable Photoelectrochemical Water Splitting

Hematite photoanodes are decorated with nanostructured FeOOH by photoelectrodeposition. An obvious cathodic shift in the photocurrent onset potential is observed, while four‐times enhancement of photocurrent density enhancement is acheived with FeOOH present. This can be ascribed to the high reaction area for the structure and high electrocatalytic activity of nanostructured FeOOH, which increases the amount of photogenerated holes involved in the water oxidation reaction and accelerates the kinetics of water oxidation. Furthermore, the obtained Fe₂O₃/FeOOH photoanode achieves considerable O₂ evolution rate (10.1 μmol h^?1 cm^?2) under AM 1.5 G illumination and is maintained for as long as 70 h. The Fe₂O₃/FeOOH films show visible light response, high photocurrent density, and long‐term stability, and they are well qualified photoanode materials and a promising candidate for photoelectrochemical water splitting.     

Co3O4 Nanoparticles as Robust Water Oxidation Catalysts Towards Remarkably Enhanced Photostability of a Ta3N5 Photoanode

Despite the fact that Ta₃N₅ absorbs a major fraction of the visible spectrum, the rapid decrease of photocurrent encountered in water photoelectrolysis over time remains a serious hurdle for the practical application of Ta₃N₅ photoelectrodes. Here, by employing a Co₃O₄ nanoparticle water oxidation catalyst (WOC) as well as an alkaline electrolyte, the photostability of Ta₃N₅ electrode is significantly improved. Co₃O₄/Ta₃N₅ photoanode exhibits the best durability against photocorrosion to date, when compared with Co(OH)_x/Ta₃N₅ and IrO₂/Ta₃N₅ photoanodes. Specifically, about 75% of the initial stable photocurrent remains after 2 h irradiation at 1.2 V vs. RHE (reversible hydrogen electrode). Meanwhile, a photocurrent density of 3.1 mA cm^?2 has been achieved on Co₃O₄/Ta₃N₅ photoanode at 1.2 V vs. RHE with backside illumination under 1 sun AM 1.5 G simulated sunlight. The reason for the relatively high stability is discussed on the basis of electron microscopic observations and photoelectrochemical measurements, and the surface nitrogen content is monitored by X‐ray photoelectron spectroscopic analysis.     

Confined Transformation of Organometal‐Encapsulated MOFs into Spinel CoFe2O4/C Nanocubes for Low‐Temperature Catalytic Oxidation

Development of spinel bimetallic oxides as low‐cost and high‐efficiency catalysts for catalytic oxidation is highly desired. However, rational design of spinel oxides with controlled structure and components still remains a challenge. A general route for large‐scale preparation of spinel CoFe₂O₄/C nanocubes transformed from organometal‐encapsulated metal–organic frameworks (MOFs) via exchange–coordination and pyrolysis combined method is reported. Strong confinement effect between organometallics and MOFs realizes reconstruction of crystal phase and composition, but not simple metallic oxides support by Co²⁺ introduction. Compared with Co₃O₄‐Fe₂O₃/C, MOFs‐derived cubic nano‐CoFe₂O₄/C with higher surface area (115.7 m² g^?1) and favorable surface chemistry exhibits excellent catalytic activity (100% CO conversion at 105 °C) and competitive water‐resisting stability (total conversion at 145 °C for 20 h). Turnover frequency of CoFe₂O₄/C reaches 4.26 × 10^?4 s^?1 at 90 °C, two orders of magnitude higher than commercial Co₃O₄ . Theoretical models show that oxygen vacancies (17.7%) at exposed {112} facet on the carbon interface take superiority in nanocubic spinel phase, which allows reactive species to be strongly adsorbed on nanostructured catalysts' surface and plays key roles in hindering deactivation under moisture rich conditions. The progresses offer a promising way in the development of novel spinel oxides with tailored architecture and properties for vast applications.     

Defect‐Rich Nitrogen Doped Co3O4/C Porous Nanocubes Enable High‐Efficiency Bifunctional Oxygen Electrocatalysis

Heteroatom doping plays a significant role in optimizing the catalytic performance of electrocatalysts. However, research on heteroatom doped electrocatalysts with abundant defects and well‐defined morphology remain a great challenge. Herein, a class of defect‐engineered nitrogen‐doped Co₃O₄ nanoparticles/nitrogen‐doped carbon framework (N‐Co₃O₄@NC) strongly coupled porous nanocubes, made using a zeolitic imidazolate framework‐67 via a controllable N‐doping strategy, is demonstrated for achieving remarkable oxygen evolution reaction (OER) catalysis. X‐ray photoelectron spectroscopy, X‐ray absorption fine structure, and electron spin resonance results clearly reveal the formation of a considerable amount of nitrogen dopants and oxygen vacancies in N‐Co₃O₄@NC. The defect engineering of N‐Co₃O₄@NC makes it exhibit an overpotential of only 266 mV to reach 10 mA cm^?2, a low Tafel slope of 54.9 mV dec^?1 and superior catalytic stability for OER, which is comparable to that of commercial RuO₂. Density functional theory calculations indicate N‐doping could promote catalytic activity via improving electronic conductivity, accelerating reaction kinetics, and optimizing the adsorption energy for intermediates of OER. Interestingly, N‐Co₃O₄@NC also shows a superior oxygen reduction reaction activity, making it a bifunctional electrocatalyst for zinc–air batteries. The zinc–air battery with the N‐Co₃O₄@NC cathode demonstrates superior efficiency and durability, showing the feasibility of N‐Co₃O₄/NC in electrochemical energy devices.     

Nitrogen‐Doped Cobalt Oxide Nanostructures Derived from Cobalt–Alanine Complexes for High‐Performance Oxygen Evolution Reactions

Taking advantage of the self‐assembling function of amino acids, cobalt–alanine complexes are synthesized by straightforward process of chemical precipitation. Through a controllable calcination of the cobalt–alanine complexes, N‐doped Co₃O₄ nanostructures (N‐Co₃O₄) and N‐doped CoO composites with amorphous carbon (N‐CoO/C) are obtained. These N‐doped cobalt oxide materials with novel porous nanostructures and minimal oxygen vacancies show a high and stable activity for the oxygen evolution reaction. Moreover, the influence of calcination temperature, electrolyte concentration, and electrode substrate to the reaction are compared and analyzed. The results of experiments and density functional theory calculations demonstrate that N‐doping promotes the catalytic activity through improving electronic conductivity, increasing OH^? adsorption strength, and accelerating reaction kinetics. Using a simple synthetic strategy, N‐Co₃O₄ reserves the structural advantages of micro/nanostructured complexes, showing exciting potential as a catalyst for the oxygen evolution reaction with good stability.     

Photodeposited FeOOH vs electrodeposited Co-Pi to enhance nanoporous BiVO4 for photoelectrochemical water splitting

Co-Pi and FeOOH cocatalysts were in-situ deposited on the surface of nanoporous BiVO₄ photoelectrodes. The FeOOH cocatalyst has little effect on the BiVO₄ samples''morphologies,while the electrodeposited Co-Pi cocatalyst seems to affect the surface of BiVO₄.The impedance intensity modulated photocurrent spectroscopy (IMPS),Mott-Schottky (M-S) techniques characterize BiVO₄ samples photoelectrochemical performance with the deposition of Co-Pi and FeOOH.The Co-Pi/BiVO₄ shows better photoelectrochemical performance than the FeOOH/BiVO₄,but the FeOOH/BiVO₄ exhibited the better stabilities.The flat band potential and slope of M-S plotof FeOOH/BiVO₄ have little variations compared with BiVO₄.In contrast,Co-Pi/BiVO₄ exhibited the down shifted flat band potential,which is beneficial for the photoelectrochemical water oxidation.The electron transfer measurements revealed that the deposition of FeOOH and Co-Pi onto BiVO₄ significantly enhanced the photoelectrochemical performance via reducing the interface resistance and promoting the electron transport.Furthermore, Co-Pi cocatalysts can further pin the transport-limiting traps and significantly facilitate the electron transport.     

Atomic‐Scale Insights into the Low‐Temperature Oxidation of Methanol over a Single‐Atom Pt1‐Co3O4 Catalyst

Heterogeneous catalysts with single‐atom active sites offer a means of expanding the industrial application of noble metal catalysts. Herein, an atomically dispersed Pt₁‐Co₃O₄ catalyst is presented, which exhibits an exceptionally high efficiency for the total oxidation of methanol. Experimental and theoretical investigations indicate that this catalyst consists of Pt sites with a large proportion of occupied high electronic states. These sites possess a strong affinity for inactive Co²⁺ sites and anchor over the surface of (111) crystal plane, which increases the metal–support interaction of the Pt₁‐Co₃O₄ material and accelerates the rate of oxygen vacancies regeneration. In turn, this is determined to promote the coadsorption of the probe methanol molecule and O₂. Density functional theory calculations confirm that the electron transfer over the oxygen vacancies reduces both the methanol adsorption energy and activation barriers for methanol oxidation, which is proposed to significantly enhance the dissociation of the C? H bond in the methanol decomposition reaction. This investigation serves as a solid foundation for characterizing and understanding single‐atom catalysts for heterogeneous oxidation reactions.