Enhanced Surface Reaction Kinetics and Charge Separation of p–n Heterojunction Co3O4/BiVO4 Photoanodes

Tri-functional molecular relay to fabricate size-controlled CoOx nanoparticles and WO3 photoanode for an efficient photoelectrochemical water oxidation

Heterojunction and element doping to couple light-harvesting semiconductors with catalytic materials have been widely employed for photoelectrochemical (PEC) water splitting.

Enhanced Photoelectrocatalytical Performance of Inorganic-Inorganic Hybrid Consisting BiVO4, V2O5, and Cobalt Hexacyanocobaltate as a Perspective Photoanode for Water Splitting

Thin layers of BiVO4/V2O5 were prepared on FTO substrates using pulsed laser deposition technique. The method of cobalt hexacyanocobaltate (Cohcc) synthesis on the BiVO4/V2O5 photoanodes consists of cobalt deposition followed by electrochemical oxidation of metallic Co in K3[Co(CN)6] aqueous electrolyte. The modified electrodes were tested as photoanodes for water oxidation under simulated sunlight irradiation. Deposited films were characterized using UV-Vis spectroscopy, Raman spectroscopy, and scanning electron microscopy. Since the V2O5 is characterized by a narrower energy bandgap than BiVO4, the presence of V2O5 shifts absorption edge (ΔE = ~0.25 eV) of modified films towards lower energies enabling the conversion of a wider range of solar radiation. The formation of heterojunction increases photocurrent of water oxidation measured at 1.2 V vs Ag/AgCl (3 M KCl) to over 1 mA cm-2, while bare BiVO4 and V2O5 exhibit 0.37 and 0.08 mA cm-2, respectively. On the other hand, the modification of obtained layers with Cohcc shifts onset potential of photocurrent generation into a cathodic direction. As a result, the photocurrent enhancement at a wide range of applied potential was achieved.

Investigation of Binary Metal (Ni, Co) Selenite as Li-Ion Battery Anode Materials and Their Conversion Reaction Mechanism with Li Ions

Highly efficient anode materials with novel compositions for Li-ion batteries are actively being researched. Multicomponent metal selenite is a promising candidate, capable of improving their electrochemical performance through the formation of metal oxide and selenide heterostructure nanocrystals during the first cycle. Here, the binary nickel-cobalt selenite derived from Ni-Co Prussian blue analogs (PBA) is chosen as the first target material: the Ni-Co PBA are selenized and partially oxidized in sequence, yielding (NiCo)SeO₃ phase with a small amount of metal selenate. The conversion mechanism of (NiCo)SeO₃ for Li-ion storage is studied by cyclic voltammetry, in situ X-ray diffraction, ex situ X-ray photoelectron spectroscopy, in situ electrochemical impedance spectroscopy, and ex situ transmission electron microscopy. The reversible reaction mechanism of (NiCo)SeO₃ with the Li ions is described by the reaction: NiO + CoO + xSeO₂ + (1 - x)Se + (4x + 6)Li⁺ + (4x + 6)e^- ↔ Ni + Co + (2x + 2)Li₂ O + Li₂ Se. To enhance electrochemical properties, polydopamine-derived carbon is uniformly coated on (NiCo)SeO₃ , resulting in excellent cycling and rate performances for Li-ion storage. The discharge capacity of C-coated (NiCo)SeO₃ is 680 mAh g^-1 for the 1500th cycle when cycled at a current density of 5 A g^-1 .

Photoinduced Carrier Dynamics at the Interface of Black Phosphorus and Bismuth Vanadate

Two-dimensional (2D) heterostructures of black phosphorus (BP)/bismuth vanadate (BVO) have attracted much attention due to their potential uses in photocatalytic water splitting. However, the interfacial photoinduced electron- and hole-transfer dynamics are not explored computationally. Herein, we have used density functional theory (DFT) calculations and DFT-based fewest-switches surface-hopping dynamics simulations to investigate the light-driven electron and hole dynamics taking place at the interface of BP and the BVO(010) surface. Our results show that the BP monolayer is adsorbed on BVO(010) via van der Waals interaction. Upon irradiation, the electron transfer takes place from BP to BVO(010) within 500 fs but with two distinct processes. In the first phase, the electron transfer proceeds adiabatically and is mainly driven by atomic motions. In the second phase, the electron transfer decays very slowly. The hole-transfer dynamics from BVO(010) to BP exhibits a similar ultrafast decay in the first stage followed by a slow decay; however, there is a comparable amount of hole trapped in a BP state due to a large energy gap from its higher state. These insights may be useful for the design of novel photocatalytic water-splitting materials.

Room-temperature hydrolysis fabrication of BiOBr/Bi12O17Br2 Z-Scheme photocatalyst with enhanced resorcinol degradation and NO removal activity

BiOBr-based photocatalysts hold great promise in the application of organic wastewater treatment and air purification. However, the catalysis ability of photocatalyst is greatly limited by its poor reduction capacity and intrinsic high recombination rate of photo-generated charge carriers. In this work, a novel direct Z-scheme BiOBr/Bi₁₂O₁₇Br₂ photocatalyst is prepared via a facile hydrolysis route at room temperature, which exhibits highly enhanced performance for resorcinol degradation and NO removal than pure Bi₁₂O₁₇Br₂ and BiOBr. The formation of the direct Z-scheme heterojunction is substantiated by radical scavenging experiments and the analysis of electronic structure, and it benefits the photocatalytic reaction by accelerating the charge separation and improving the redox ability. Finally, the underlying photocatalytic mechanism is elucidated based on the band structure and radical scavenging experiments. This study provides a facile strategy for bismuth halide Z-scheme heterojunction constructing at room temperature and also sheds light on highly efficient photocatalysts designing.

Multiple Anionic Transition-Metal Oxycarbide for Better Lithium Storage and Facilitated Multielectron Reactions

As an important class of multielectron reaction materials, the applications of transition-metal oxides (TMOs) are impeded by volume expansion and poor electrochemical activity. To address these intrinsic limitations, the renewal of TMOs inspires research on incorporating an advanced interface layer with multiple anionic characteristics, which may add functionality to support properties inaccessible to a single-anion TMO electrode. Herein, a transition-metal oxycarbide (TMOC, M = Mo) with more than one anionic species was prepared as an interface layer on a corresponding oxide. A multiple anionic TMOC possesses advantages of structural stability, abundant active sites, and elevated metal cation valence states. Such merits mitigate volume changes and enhance multielectron reactions significantly. The TMOC nanocomposite has a well-maintained capacity after 1000 cycles at 2 A·g^-1 and fully resumed rate performance. In situ synchrotron X-ray powder diffraction (SXRPD) analysis unveils negligible volume expansions occurring upon oxycarbide layer coupling, with lattice spacing variation less than 1% during cycling. The lithium storage mechanism is further inspected by combined analysis of kinetics, SXRPD, and first-principles calculations. Superior to TMO, multielectron reactions of the TMOC electrode have been boosted due to easier rupture of the metal-oxygen bond. Such improvements underscore the importance of incorporating an oxycarbide configuration as a strategy to expand applications of TMOs.

Boosting Sodium Storage of Fe1-xS/MoS2 Composite via Heterointerface Engineering

Improving the cycling stability of metal sulfide-based anode materials at high rate is of great significance for advanced sodium ion batteries. However, the sluggish reaction kinetics is a big obstacle for the development of high-performance sodium storage electrodes. Herein, we have rationally engineered the heterointerface by designing the Fe_1-xS/MoS₂ heterostructure with abundant "ion reservoir" to endow the electrode with excellent cycling stability and rate capability, which is proved by a series of in and ex situ electrochemical investigations. Density functional theory calculations further reveal that the heterointerface greatly decreases sodium ion diffusion barrier and facilitates charge-transfer kinetics. Our present findings not only provide a deep analysis on the correlation between the structure and performance, but also draw inspiration for rational heterointerface engineering toward the next-generation high-performance energy storage devices.

Earth-Abundant MoS2 and Cobalt Phosphate Dual Cocatalysts on 1D CdS Nanowires for Boosting Photocatalytic Hydrogen Production

Cocatalysts play a significant role in accelerating the catalytic reactions of semiconductor photocatalyst. In particular, a semiconductor assembled with dual cocatalysts, i.e., reduction and oxidation cocatalysts, can obviously enhance the photocatalytic performance because of the synergistic effect of fast consumption of photogenerated electrons and holes simultaneously. However, in most cases, noble metal cocatalysts are employed, which tremendously increases the cost of the photocatalysts and restricts their large-scale applications. Herein, on the platform of one-dimensional (1D) CdS nanowires, we have utilized the earth-abundant dual cocatalysts, MoS₂ and cobalt phosphate (Co-Pi), to construct the CdS@MoS₂@Co-Pi (CMC) core-shell hybrid photocatalysts. In this dual-cocatalyst system, Co-Pi is in a position to expedite the migration of holes from CdS, while MoS₂ acts as an electron transporter as well as active sites to accelerate the surface water reduction reaction. Taking the advantages of the dual-cocatalyst system, the prepared CMC hybrid shows an obvious enhancement of both the photoactivity and photostability toward hydrogen production compared with bare 1D CdS nanowires and binary hybrids (CdS@MoS₂ and CdS@Co-Pi). This work highlights the promising prospects for rational utilization of earth-abundant dual cocatalysts to design low-cost and efficient hybrids toward boosting photoredox catalysis.

Enhancing photoelectrochemical water splitting by combining work function tuning and heterojunction engineering

We herein demonstrate the unusual effectiveness of two strategies in combination to enhance photoelectrochemical water splitting. First, the work function adjustment via molybdenum (Mo) doping significantly reduces the interfacial energy loss and increases the open-circuit photovoltage of bismuth vanadate (BiVO₄) photoelectrochemical cells. Second, the creation and optimization of the heterojunction of boron (B) doping carbon nitride (C₃N₄) and Mo doping BiVO₄ to enforce directional charge transfer, accomplished by work function adjustment via B doping for C₃N₄, substantially boost the charge separation of photo-generated electron-hole pairs at the B-C₃N₄ and Mo-BiVO₄ interface. The synergy between the above efforts have significantly reduced the onset potential, and enhanced charge separation and optical properties of the BiVO₄-based photoanode, culminating in achieving a record applied bias photon-to-current efficiency of 2.67% at 0.54 V vs. the reversible hydrogen electrode. This work sheds light on designing and fabricating the semiconductor structures for the next-generation photoelectrodes.

While photoelectrodes represent a promising solar-to-fuel conversion technology, material challenges limit performances. Here, authors improve the onset potential and charge separation of bismuth vanadate photoanode water splitting performances by work function tuning and heterojunction engineering.

ZIF-67-Derived 3D Hollow Mesoporous Crystalline Co3 O4 Wrapped by 2D g-C3 N4 Nanosheets for Photocatalytic Removal of Nitric Oxide

ZIF-67-derived 3D hollow mesoporous crystalline Co₃ O₄ wrapped by 2D graphitic carbon nitride (g-C₃ N₄ ) nanosheets are prepared by low temperature annealing, and are used for the photocatalytic oxidation of nitric oxide (NO) at a concentration of 600 ppb. The p-n heterojunction between Co₃ O₄ and g-C₃ N₄ forms a spatial conductive network frame and results in a broad visible light response range. The hollow mesoporous structure of Co₃ O₄ contributes to the circulation and adsorption of NO, and the large specific surface area exposes abundant active sites for the reaction of active species. A maximum NO degradation efficiency of 57% is achieved by adjusting the mass of the Co₃ O₄ precursor. Cycling tests and X-ray diffraction indicate the high stability and recyclability of the composite, making it promising in environmental purification applications.

The Development of Cocatalysts for Photoelectrochemical CO2 Reduction

The ever-increasing anthropogenic consumption of fossil fuels and the resulting large emission of CO₂ have led to a severe energy crisis and climate change. Photocatalytic reduction of CO₂ into fuels using solar energy is considered as a promising way to address these two problems. In particular, photoelectrochemical (PEC) reduction of CO₂ can integrate and optimize the advantages of both photocatalysis and electrocatalysis for improved conversion efficiency and selectivity. In addition to the charge generation and separation, the efficient reduction of CO₂ on the surface of a semiconductor-based photoelectrode remains a scientifically critical challenge, which can be greatly enhanced by the surface modification of cocatalysts. Herein, the recent developments of cocatalysts in PEC CO₂ reduction over semiconductor-based photoelectrodes are described, and the basic principles of PEC CO₂ reduction and the function of the cocatalyst in photoelectrocatalysis are discussed. The structure optimization between the photoelectrodes and the cocatalysts is also summarized since the loading of cocatalyst may shield the incident light and hinder charge transfer between them. Furthermore, the challenges and perspectives for PEC reduction of CO₂ are also presented.

p-n-Sensitized Heterostructure Co3O4/Fullerene with Highly Efficient Photoelectrochemical Performance for Ultrasensitive DNA Detection

Significantly sensitized architectures meeting the requirements of high photoelectric conversion efficiency and promising photocurrent intensity are extremely desirable, but challenges in sensitizer development and efficiency in photoelectrochemical (PEC) fields remain. In this paper, the p-type metal oxide semiconductor Co₃O₄ was attached as an effective photosensitizer to n-type fullerene C₆₀ in view of appropriately matched energy band levels to form the highlighted p-n-sensitized heterostructure Co₃O₄/fullerene, with facilitated charge separation and accelerated carrier mobility. Compared with traditional p-n heterostructure, the p-n-sensitized heterostructure Co₃O₄/fullerene illustrated a wider range for light absorption with further enhanced light-harvesting capability, thereby leading to more exceptional PEC performance containing remarkably promoted photoelectric conversion efficiency and improved photocurrent intensity. Impressively, the photocurrent intensity obtained by Co₃O₄/fullerene was about sixfold higher than that of fullerene alone, and this achievement was quite favored compared to the reported works for fullerene sensitization, which could be responsible for the advancement of detection sensitivity for the subsequently constructed biosensor. Unambiguously, given the p-n-sensitized heterostructure Co₃O₄/fullerene of high PEC activity, the well-fabricated three-dimensional DNA walker applied as a target-cascade signal amplification strategy, and the Au layer employed as the specific linker between the photoactive material and the signal amplification product, a smart PEC biosensor was successfully enabled for ultrasensitive investigation of the model DNA (a fragment of the p53 gene), showing a wide linear range of 60 to 1 × 10⁵ aM and a detection limit of 20 aM. This proposed PEC biosensor provided acceptable insights into the clinic analysis, disease therapies, and other relevant subjects.

Strategies of Anode Materials Design towards Improved Photoelectrochemical Water Splitting Efficiency

This review presents the latest processes for designing anode materials to improve the efficiency of water photolysis. Based on different contributions towards the solar-to-hydrogen efficiency, we mainly review the strategies to enhance the light absorption, facilitate the charge separation, and enhance the surface charge injection. Although great achievements have been obtained, the challenges faced in the development of anode materials for solar energy to make water splitting remain significant. In this review, the major challenges to improve the conversion efficiency of photoelectrochemical water splitting reactions are presented. We hope that this review helps researchers in or coming to the field to better appreciate the state-of-the-art, and to make a better choice when they embark on new research in photocatalytic water splitting.

Understanding the Roles of NiOx in Enhancing the Photoelectrochemical Performance of BiVO4 Photoanodes for Solar Water Splitting

Solar water oxidation is considered as a promising method for efficient utilization of solar energy and bismuth vanadate (BiVO₄ ) is a potential photoanode. Catalyst loading on BiVO₄ is often used to tackle the limitations of charge recombination and sluggish kinetics. In this study, amorphous nickel oxide (NiO_x ) is loaded onto Mo-doped BiVO₄ by photochemical metal-organic deposition method. The resulting NiO_x /Mo:BiVO₄ photoanodes demonstrate a two-fold improvement in photocurrent density (2.44 mA cm^-2 ) at 1.23 V versus reversible hydrogen electrode (RHE) compared with the uncatalyzed samples. After NiO_x modification the charge-separation and charge-transfer efficiencies improve significantly across the entire potential range. It is further elucidated by open-circuit photovoltage (OCP), time-resolved-microwave conductivity (TRMC), and rapid-scan voltammetry (RSV) measurements that NiO_x modification induces larger band bending and promotes efficient charge transfer on the surface of BiVO₄ . This work provides insight into designing BiVO₄ -catalyst assemblies by using a simple surface-modification route for efficient solar water oxidation.

Black phosphorene as a hole extraction layer boosting solar water splitting of oxygen evolution catalysts

As the development of oxygen evolution co-catalysts (OECs) is being actively undertaken, the tailored integration of those OECs with photoanodes is expected to be a plausible avenue for achieving highly efficient solar-assisted water splitting. Here, we demonstrate that a black phosphorene (BP) layer, inserted between the OEC and BiVO₄ can improve the photoelectrochemical performance of pre-optimized OEC/BiVO₄ (OEC: NiOOH, MnO_x, and CoOOH) systems by 1.2∼1.6-fold, while the OEC overlayer, in turn, can suppress BP self-oxidation to achieve a high durability. A photocurrent density of 4.48 mA·cm⁻² at 1.23 V vs reversible hydrogen electrode (RHE) is achieved by the NiOOH/BP/BiVO₄ photoanode. It is found that the intrinsic p-type BP can boost hole extraction from BiVO₄ and prolong holes trapping lifetime on BiVO₄ surface. This work sheds light on the design of BP-based devices for application in solar to fuel conversion, and also suggests a promising nexus between semiconductor and electrocatalyst.

Photoelectrochemical water splitting affords an integrated approach for converting light to fuel, but devices typically suffer poor activities and stabilities. Here, authors incorporate black phosphorene into bismuth vanadate photoanodes to boost hole extraction and device lifetimes.

Enhanced visible-light-driven photocatalytic disinfection using AgBr-modified g-C3N4 composite and its mechanism

In this study, novel AgBr-modified g-C₃N₄ (AgBr/g-C₃N₄) photocatalysts were prepared by an adsorption-deposition method and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and ultraviolet-visible spectroscopy (UV-vis). Furthermore, the photocatalytic disinfection performance on Escherichia coli (ATCC 15597) was investigated. The as-prepared photocatalysts exhibited well crystalline structures and morphologies with C₃N₄ and exhibited a stronger bacterial inactivation than that of pristine g-C₃N₄. The disinfection efficiency reached up to 4.80 log under 150 min of visible light irradiation when AgBr-modified g-C₃N₄ was prepared at a molar ratio of 1:5 (AgBr: g-C₃N₄), which was a 4.2 log increase compared with that of pristine g-C₃N₄ under the same experimental conditions. The enhancement of the photocatalytic activity of AgBr/g-C₃N₄ was attributed to the effective production and transfer of the photo-induced electrons under visible light irradiation, since the AgBr modification reduced the bandgap energy and boarded the visible light area. Furthermore, h⁺ was found to be the dominant contributor for bacterial inactivation. The h⁺ and photo-generated reactive oxygen species (ROSs) damaged the cell membranes and destroyed metabolic processes, resulting in leakage of potassium ions and proteins, lipid peroxidation, degradation of intracellular protein, and a reduction of the ATP levels, which finally lead to bacterial death. These results provide a theoretical basis for the development of low-cost, high-efficiency photocatalysts for green/sustainable water disinfection.

Heterostructure of 1D Ta3 N5 Nanorod/BaTaO2 N Nanoparticle Fabricated by a One-Step Ammonia Thermal Route for Remarkably Promoted Solar Hydrogen Production

Heterostructures are widely fabricated for promotion of photogenerated charge separation and solar cell/fuel production. (Oxy)nitrides are extremely promising for solar energy conversion, but the fabrication of heterostructures based on nitrogen-containing semiconductors is still challenging. Here, a simple ammonia thermal synthesis of a heterostructure (denoted as Ta₃ N₅ /BTON) composed of 1D Ta₃ N₅ nanorods and BaTaO₂ N (BTON) nanoparticles (0D), which is demonstrated to result in a remarkable increase in photogenerated charge separation and solar hydrogen production from water, is introduced. As analyzed and discussed, the Ta₃ N₅ /BTON heterostructure is type II and tends to create intimate interfaces between the 1D nanorods and 0D nanoparticles. The 1D Ta₃ N₅ nanorods are demonstrated to transfer electrons along the rod orientation direction. Furthermore, the intimate interfaces of the heterostructure are believed to originate from the similar Ta-based octahedron units of Ta₃ N₅ and BTON. All of the above features are expected to integrally endow increased photoinduced charge separation and one order of magnitude higher solar overall water splitting activity with respect to counterpart systems. These results may open a new avenue to fabricate heterostructures on the basis of nitrogen-containing semiconductors that is extremely promising for solar energy conversion.

Atomically dispersed nickel-nitrogen-sulfur species anchored on porous carbon nanosheets for efficient water oxidation

Developing low-cost electrocatalysts to replace precious Ir-based materials is key for oxygen evolution reaction (OER). Here, we report atomically dispersed nickel coordinated with nitrogen and sulfur species in porous carbon nanosheets as an electrocatalyst exhibiting excellent activity and durability for OER with a low overpotential of 1.51 V at 10 mA cm^-2 and a small Tafel slope of 45 mV dec^-1 in alkaline media. Such electrocatalyst represents the best among all reported transition metal- and/or heteroatom-doped carbon electrocatalysts and is even superior to benchmark Ir/C. Theoretical and experimental results demonstrate that the well-dispersed molecular S|NiN_x species act as active sites for catalyzing OER. The atomic structure of S|NiN_x centers in the carbon matrix is clearly disclosed by aberration-corrected scanning transmission electron microscopy and synchrotron radiation X-ray absorption spectroscopy together with computational simulations. An integrated photoanode of nanocarbon on a Fe₂O₃ nanosheet array enables highly active solar-driven oxygen production.

Dual Quantum Dot-Decorated Bismuth Vanadate Photoanodes for Highly Efficient Solar Water Oxidation

Photo-induced charge separation and photon absorption play important roles in determining the performance of the photoelectrocatalytic water splitting process. In this work, we utilize dual quantum dots (QDs), consisting of BiVO₄ and carbon, to fabricate a hybrid homojunction-based BiVO₄ photoanode for efficient and stable solar water oxidation. Formation of homojunctions, by decorating as-prepared BiVO₄ substrate with BiVO₄ QDs, enhances the charge separation efficiency by 1.3 times. This enhancement originates from lattice match, which benefits charge transfer across the interface. Furthermore, the use of carbon QDs as a stable photosensitizer effectively extends the photon absorption limit from 520 nm to over 700 nm, yielding an incident photon-to-electron conversion efficiency of 6.0 %, even at 600 nm at 1.23 V versus RHE. Finally, a remarkable photocurrent density of 6.1 mA cm^-2 at 1.23 V was recorded after depositing FeOOH/NiOOH as cocatalysts, thereby, reaching 82 % of the theoretical efficiency for BiVO₄ .

Insights of Diffusion Doping in Formation of Dual-Layered Material and Doped Heterostructure SnS-Sn:Sb2S3 for Sodium Ion Storage

Insights into the formation mechanism of a dual-layered and doped heterostructure material Sn^IIS-Sn^IV:Sb₂S₃ are reported. In the presence of mixed alkyl thiols, first nanotubes of Sb₂S₃ were formed, and upon introduction of Sn(IV), Sn^IIS was deposited onto the surface of these tubular structures. Upon further annealing at a constant temperature, sluggish transformation resulted in a Sn(II)S-Sn(IV) doped Sb₂S₃ heterostructure, which finally turned to flake-like layered doped Sb₂S₃ nanostructures. SnS and Sb₂S₃, both being layered materials, were explored for the study of Na-ion storage, and these heterostructures were observed to be superior in comparison to the individual materials as well as the final doped nanostructures. The mechanism of formation of the heterostructures, the epitaxy at the junction, the diffusion doping, and the dopant-induced axial exfoliations leading to the final doped structures were studied. The electrochemical conversions in the presence of Na ions were also investigated, and insights into the mechanisms of both are reported in this Letter.

Adjusting the Reduction Potential of Electrons by Quantum Confinement for Selective Photoreduction of CO2 to Methanol

The production of CH₃ OH from the photocatalytic CO₂ reduction reaction (PCRR) presents a promising route for the clean utilization of renewable resources, but charge recombination, an unsatisfying stability and a poor selectivity limit its practical application. In this paper, we present the design and fabrication of 0D/2D materials with polymeric C₃ N₄ nanosheets and CdSe quantum dots (QDs) to enhance the separation and reduce the diffusion length of charge carriers. The rapid outflow of carriers also restrains self-corrosion and consequently enhances the stability. Furthermore, based on quantum confinement effects of the QDs, the energy of the electrons could be adjusted to a level that inhibits the hydrogen evolution reaction (HER, the main competitive reaction to PCRR) and improves the selectivity and activity for CH₃ OH production from the PCRR. The band structures of photocatalysts with various CdSe particle sizes were also investigated quantitatively to establish the relationship between the band energy and the photocatalytic performance.

Manipulation of Charge Transport by Metallic V13 O16 Decorated on Bismuth Vanadate Photoelectrochemical Catalyst

Conductive metal oxides represent a new category of functional material with vital importance for many modern applications. The present work introduces a new conductive metal oxide V₁₃ O₁₆ , which is synthesized via a simplified photoelectrochemical procedure and decorated onto the semiconducting photocatalyst BiVO₄ in controlled mass percentages ranging from 25% to 37%. Owing to its excellent conductivity and good compatibility with oxide materials, the metallic V₁₃ O₁₆ -decorated BiVO₄ hybrid catalyst shows a high photocurrent density of 2.2 ± 0.2 mA cm^-2 at 1.23 V versus reversible hydrogen electrode (RHE). Both experimental characterization and density functional theory calculations indicate that the superior photocurrent derives from enhanced charge separation and transfer, resulting from ohmic contact at the interface of mixed phases and superior electrical conductivity from V₁₃ O₁₆ . A Co-Pi coating on BiVO₄ -V₁₃ O₁₆ further increases the photocurrent to 5.0 ± 0.5 mA cm^-2 at 1.23 V versus RHE, which is among the highest reported for BiVO₄ -based photoelectrodes. Surface photovoltage and transient photocurrent measurements suggest a charge-transfer model in which photocurrents are enhanced by improved surface passivation, although the barrier at the Co-Pi/electrolyte interface limits the charge transfer.

WO3/BiVO4 Type-II Heterojunction Arrays Decorated with Oxygen-Deficient ZnO Passivation Layer: A Highly Efficient and Stable Photoanode

In the present work, we report a ternary WO₃/BiVO₄/ZnO photoanode with boosted PEC efficiency and stability toward highly efficient water splitting. The type-II WO₃/BiVO₄ heterojunction arrays are firstly prepared by hydrothermal growth of WO₃ nanoplate arrays onto the substrates of fluorine-doped tin oxide (FTO)-coated glass, followed by spin-coating of BiVO₄ layers onto the WO₃ nanoplate surfaces. After that, thin ZnO layers are further introduced onto the WO₃/BiVO₄ heterojunction arrays via atomic layer deposition (ALD), leading to the construction of ternary WO₃/BiVO₄/ZnO photoanodes. It is verified that the ZnO thin layer in the WO₃/BiVO₄/ZnO photoanode contains abundant oxygen vacancies, which could act as an effective passivation layer to enhance the charge separation and surface water oxidation kinetics of photogenerated carriers. The as-prepared WO₃/BiVO₄/ZnO photoanode produces a photocurrent of 2.96 mA cm^-2 under simulated sunlight with an incident photon-to-current conversion efficiency (IPCE) of ∼72.8% at 380 nm at a potential of 1.23 V versus RHE without cocatalysts, both of which are comparable to the state-of-the-art WO₃/BiVO₄ counterparts. Moreover, the photocurrent of the WO₃/BiVO₄/ZnO photoanode shows only 9% decay after 6 h, suggesting its high photoelectrochemical (PEC) stability.

Defected ZnWO4-decorated WO3 nanorod arrays for efficient photoelectrochemical water splitting

The utilization of solar energy in photoelectrochemical water splitting is a popular approach to store solar energy and minimize the dependence on fossil fuels. Herein, defected ZnWO₄-decorated WO₃ nanorod arrays with type II heterojunction structures were synthesized via a two-step solvothermal method. By controlling the amount of Zn precursor, WO₃ nanorods were decorated in situ with tunable amounts of ZnWO₄ nanoparticles. Characterization confirmed the presence of abundant W⁵⁺ species in the defected ZnWO₄-decorated WO₃ samples, leading to enhanced light absorption and charge-separation efficiency. Therefore, the decorated WO₃ nanorod arrays show much higher photoelectrochemical (PEC) activity than pure WO₃ nanorod arrays. Specifically, the sample with optimal ZnWO₄ decoration and surface defects exhibits a current density of 1.87 mA cm⁻² in water splitting at 1.23 V vs. RHE under 1 sun irradiation (almost 2.36 times higher than that of pure WO₃), a high incident photon-to-current efficiency of nearly 40% at 350 nm, and a relatively high photostability. However, the decoration of WO₃ with too much ZnWO₄ blocks the light absorption of WO₃, inhibiting the PEC performance, even when many defects are present. This work provides a promising approach to rationally construct defected heterojunctions as highly active PEC anodes for practical applications.

A strategy based on a solvothermal method was developed to construct defected ZnWO₄-decorated WO₃ photoanodes for efficient photoelectrochemical water splitting.

Rational design of yolk–shell nanostructures for photocatalysis

Yolk–shell structures provide an ideal platform for the rational regulation and effective utilization of charge carriers because of their void space and large surface areas. Furthermore, the efficiency of charge behavior in every step can be further improved by many strategies. This review describes the synthesis of yolk–shell structures and their effect for the enhancement of heterogeneous photocatalysis.

ZnO nanorods modified with noble metal-free Co3O4 nanoparticles as a photocatalyst for efficient ethylene degradation under light irradiation

ZnO modified with noble metal-free Co₃O₄ nanoparticles was prepared by a simple method and showed good stability and high efficiency for photo-oxidizing ethylene.

Modification strategies for enhancing the visible light responsive photocatalytic activity of the BiPO4nano-based composite photocatalysts

The present issues related to environmental purification have led to a great need for the development of a superior oxidation process to solve the life-threatening problem. The use of the BiPO₄nanomaterial in photocatalysis is one of the best methods for the treatment of wastewater due to its less harmful nature.

Analysis of the interfacial characteristics of BiVO4/metal oxide heterostructures and its implication on their junction properties

Throughin situphotoelectron spectroscopy, the interface properties of BiVO₄/NiO, BiVO₄/CoO_xand BiVO₄/ITO were investigated.

Highly conformal deposition of ultrathin cobalt acetate on a bismuth vanadate nanostructure for solar water splitting

In this work, the effect of photochemically modifying nanoporous bismuth vanadate in Co²⁺ solution in acetate buffer (abbreviated as Co–Ac) on water oxidation was thoroughly studied.