Controlling Bismuth Vanadate Morphology and Crystalline Structure through Optimization of Microwave-Assisted Synthesis Conditions

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.