Photoelectrochemical (PEC) water splitting has become an attractive way to sustainable hydrogen production. Herein, a cobalt ion-doped BiVO 4 photoanode (Co:BiVO 4 ) is prepared by an electrodeposition-solution drop-casting strategy. Co:BiVO 4 presents a threedimensional coral sheet structure with Co 3 O 4 particles on the surface. The surface will be covered with an ultrathin cobalt borate (CoB i ) film after PEC testing in borate buffer. The photocurrent density of Co:BiVO 4 reaches 4.45 mA/cm 2 at 1.23 V RHE (2.46 times that of BiVO 4 ). Co:BiVO 4 also exhibits self-healing properties in borate buffer during the PEC test. The excellent PEC performance of the Co:BiVO 4 photoanode is due to the synergy effect caused by Co doping. Some of the Co ions are doped into the BiVO 4 lattice to increase the electronic conductivity. Excess Co ions form the Co 3 O 4 co-catalyst on the BiVO 4 surface to promote the water oxidation reaction. After PEC testing in borate buffer, the CoB i film covering the Co:BiVO 4 surface acts as a cocatalyst to provide more active sites for water oxidation. The applied bias photon-to-current efficiency, charge separation, and injection efficiency of the Co:BiVO 4 photoanode are 0.94%, 63.19%, and 87.73% (3.62, 2.39, and 2.95 times that of bare BiVO 4 ). This work provides a wealth of insights into the influence of Co:BiVO 4 on PEC water oxidation in borate buffer and demonstrates the self-healing function of the system.

BiVO4 is one of the most attractive photoanode materials for photoelectrochemical water splitting. Herein, cobalt phosphate (CoPi) modified BiVO4 (BiVO4/CoPi) photoanode is prepared by electrodeposition. The physical and chemical characterization...

Photoelectrochemical (PEC) water splitting is a practical way of solar energy storage. In this instance, a ternary WO3/BiVO4/NiOOH photoanode is prepared using sol–gel and photoelectric deposition processes. Images from a scanning electron microscope and transmission electron microscope reveal that coral flake-shaped BiVO4 is coated on WO3 nanorods and that BiVO4/WO3 is dotted with many NiOOH nanoparticles. WO3/BiVO4/NiOOH has a photoresponse (3.00 mA/cm2 at 1.23 VRHE) that is 7 times greater than that of bare BiVO4. According to UV–vis spectra and Mott–Schottky analyses, holes can move from the valence band of WO3 (2.76 eV) to that of BiVO4 (2.52 eV), while electrons can move from the conduction band of BiVO4 (0.05 eV) to that of WO3 (0.16 eV). The photogenerated carriers’ transport is efficiently driven by the well-matched WO3/BiVO4 heterojunction. After NiOOH modification, the interfacial carriers’ transfer resistance of WO3/BiVO4/NiOOH (148.2 Ω) is reduced by a quarter. NiOOH, as a water oxidation cocatalyst, accelerates the water oxidation kinetics. Due to the synergy between WO3/BiVO4 heterojunction and NiOOH cocatalyst, the charge separation and injection efficiency of WO3/BiVO4/NiOOH reach 39.99% and 50.05% (7.04 and 6.11 times that of bare BiVO4). The WO3/BiVO4/NiOOH photocurrent density retains 78% of its initial value after the 10 h stability test. The uniformly distributed NiOOH physically isolates the photoanode surface from the electrolyte, which inhibits the BiVO4 and WO3 photocorrosion. This research may help explain how the WO3/BiVO4 heterojunction and NiOOH cocatalyst work together to boost PEC water splitting.

Photoelectrochemical water splitting is an attractive and clean approach for hydrogen and oxygen evolution. The α-Fe2O3–H@CoO–H/Ti foil (TF) synthesized by two-step calcination process is used as a photoanode for solar to hydrogen energy. The scanning electron microscopy and transmission electron microscopy indicate the multi-level nanowheat-like structure with defects on the surface. It is favorable for light absorption and separation of the charge carrier. The crystal structure and composition were analyzed by the X-ray diffraction, Raman, X-ray fluorescence, and X-ray photoelectron spectroscopy studies. The photocurrent density of α-Fe2O3–H@CoO–H/TF is 1.60 mA/cm2 at 1.23 V versus reversible hydrogen electrode (RHE) and 14.63 mA/cm2 at 1.6 V versus RHE. The resistance and combination of the charge carrier at the interface of the photoanode/electrolyte and photoanode/TF are greatly decreased from electrochemical impedance spectroscopy. The collaborative improvement of the nanowheat-like morphology, residual little Co element as the oxygen evolution reaction catalyst, and oxygen vacancy in the surface defect after the hydrogen calcination are significant for photoelectrochemical water splitting.

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