Bismuth vanadate has been widely used in photocatalysis and photoelectrocatalysis due to its physical and chemical properties; for these applications, the control of the crystalline structure and morphology is essential. The development of methodologies to improve the control of these parameters is usually very time and energy-consuming, and further studies require several experiments. In this context, the use of microwave irradiation as a heating source is desirable, since it drastically reduces the reaction time. However, the unique interaction of the microwave with the reactional species makes the development of microwave-assisted synthesis protocols a big challenge. Here, we report a study on how the solvent (water, water/ethanol 1:1, ethanol, and ethylene glycol), pH (1–14), the use of hexadecyltrimethylammonium bromide (CTAB), and solvothermal vs reflux conditions affect the crystalline structure and morphology of BiVO4 nanomaterials prepared by microwave-assisted methods. We found that monoclinic and tetragonal BiVO4 are obtained in acidic media. Also, the use of water and water/ethanol as solvents results in 2D nanomaterials, whereas nanoparticles are observed by using ethanol and ethylene glycol. Finally, the use of CTAB and hydrothermal conditions leads to smaller and denser particles.

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.

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