H2V3O8 single-crystal nanobelts: Hydrothermal preparation and formation mechanism

The formation mechanism of highly pure H2V3O8 single-crystal nanobelts is clarified in a hydrothermal synthesis process with a specially designed precursor solution containing V5+ and V4+ in a fixed ratio of 2/1. This specially designed precursor solution provides an additional merit for the rapid fabrication of highly pure H2V3O8 nanobelts through a simple hydrothermal route. During the hydrothermal synthesis process, V5+ species initially reacts with some V4+ to form a metastable, whisker-like V10O24 · nH2O (n < 12). The V5+ species dissolved from the whisker-like V10O24 · nH2O reacts continuously with residual V4+ ions in the precursor solution to form seeds of H2V3O8 single-crystals. The anisotropic growth of H2V3O8 single-crystal nanobelts with length > 10 μm and width between 50 and 150 nm occurs with prolonging the hydrothermal time. Finally, highly pure H2V3O8 single-crystal nanobelts are obtained when the hydrothermal time reaches 4 h. The textures of vanadium oxides prepared at different hydrothermal times are systematically compared through X-ray diffraction, transmission electron microscopic and X-ray photoelectron spectroscopic analyses to clarify the synthesis mechanism of H2V3O8 single-crystal nanobelts.