Ultrasonic-Improved Bismuth Vanadate Precursor Preparation for Superior Tungsten Oxide/Bismuth Vanadate Photoanode Performance in Water Oxidation and Dye Degradation Processes

Abstract

Photoelectrocatalytic (PEC) applications require the development of efficient fabrication methods for high-performance photoanodes. This study utilizes an automated layer-by-layer dip-coating technique to overcome the limitations of traditional manual dip-coating by incorporating ultrasonic-assisted preparation of bismuth vanadate (BiVO4) precursor solutions for fabricating tungsten oxide (WO3)/BiVO4 photoanodes. The proposed technique demonstrated excellent scalability, reproducibility, and enhanced PEC performance. Ultrasonic treatment for 120 minutes significantly increased the photocurrent density to 3 mA/cm2 under visible light, as confirmed by electrochemical impedance spectroscopy and field emission scanning electron microscopy experiments. These improvements are attributed to higher constant phase element values, lower charge transfer resistance, and greater surface roughness and porosity. The monoclinic crystalline structure of BiVO4 was confirmed by X-ray diffraction, indicating a reduced bandgap energy of 1.9 eV, in contrast to the original 2.4 eV, thereby enhancing visible light absorption. The WO3/BiVO4 photoanode eliminated 99% of organic dye in 20 minutes and showed considerable endurance over multiple cycles, indicating substantial production of hydroxyl radicals (•OH). These findings demonstrate the capacity of the method for extensive electrode fabrication and its importance for PEC applications in environmental remediation and sustainable energy conversion. ©The Author(s) 2025.