Influence of the Solvent Used for Microwave-Assisted Synthesis of W-BiVO4 on Properties and Photoelectroactivity of W-BiVO4/WO3

W-BiVO4 and WO3 are promising photoanodes for the oxygen evolution reaction (OER). The synthesis procedure determines morphology, composition, and consequently, the photo(electro)chemical performance. W-BiVO4 was produced through a microwave-assisted hydrothermal method, using ethanol (EtOH) or ethylene glycol (EG) as solvents, resulting in the materials W-BiVO4(EtOH) and (BiVO4(EG), respectively. WO3 films were grown onto a conductor substrate under microwave-assisted hydrothermal conditions. W-BiVO4/WO3 was prepared through drop-casting and applied as photoanodes for OER. Morphology, crystalline structure, chemical composition, and band gap energy were evaluated. Also, the electrochemical behavior and interfacial properties were investigated via surface interrogation (SI-SECM). It has been observed that the photoelectroactivity of W-BiVO4(EG)/WO3 is 16 times higher than W-BiVO4(EtOH)/WO3 due to its favorable band edge alignment toward OER. SI-SECM showed that W-BiVO4(EtOH)/WO3 exhibited a surface coverage of reactive oxygen species four times higher than W-BiVO4(EG)/WO3. The contrasting reactivity was ascribed to differences in morphology and crystalline structure of W-BiVO4.