Bismuth vanadate (BiVO4) nanostructures represent materials with high sensibility toward visible radiation, in addition to unique physical-chemical properties that allow their application in photochemistry. These catalysts can be synthesized through microwave-assisted routes, an emergent technique that allows quickly obtaining of the desired products, with high selectivity, high yields and low energetic consumption, in comparison to conventional synthesis methods. In this work, we describe the optimization of the synthetic condition to obtain BiVO4 with controlled morphology and structure using micro-wave irradiation as heating source. The evaluated parameters included pH (1-14), solvent (water, water: ethanol 1:1, pure ethanol and ethylene glycol), CTAB (hexadecyltrimethylammonium bromide) addition, and pressure conditions (reflux or solvothermal synthesis). The results revealed that most obtained material were composed by mixtures of tetragonal and monoclinic crystalline BiVO4 structures, and the mixture proportion influenced by the pH of the reaction. Amorphous materials were obtained when the syntheses were performed at pH above 10. The use of ethanol or ethylene glycol induces the nucleation instead of growing process, and, as a result, globular morphology was observed. Addition of CTAB also induces the nucleation process, however it favors the formation of single monoclinic nanostructure. Finally, it wasn’t observed influence of pressure over the morphology or crystalline structure of the obtained materials, which was ascribed to the low temperature used during the solvothermal syntheses (solvent boiling temperature). In conclusion, we found that BiVO4 with single morphology and monoclinic structure (which is the most desired phase for photocatalytic purposes) can be obtained using water as solvent, by adding CTAB, at low pH and under reflux, as showed in the Raman spectra and scanning electron microscopy in Figure 1.

Microwave-assisted routes for bismuth nanostructures

254th National Meeting (2017)

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