Boosting Photoelectrochemical Performance of BiVO<sub>4</sub> Photoanode by Synergistic Effect of WO<sub>3</sub>/BiVO<sub>4</sub> Heterojunction Construction and NiOOH Water Oxidation Cocatalyst Modification
Wanqing Fang, Yimin Lin, Rongzi Xv, Li Fu
Abstract
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.