Facile Hydrothermal Synthesis of Vanadium Oxide Nanosheets from Ammonium Metavanadate-Formic Acid System and its Mechanism

Pure VO2(B) nanosheets have been synthesized by hydrothermal strategy using ammonium metavanadate (NH4VO3) as vanadium source and formic acid (HCOOH) as reduce agent. The composition and morphology of the nanosheets were established by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The as-obtained VO2(B) nanosheets have a length of 100nm~2 μm, a wideness of 100nm~300 nm and a thickness of 30–60 nm. The shape is irregular and the edge is rough, uneven. The pressure and gas liquid equilibrium in hydrothermal system at different temperatures, different fill rate is analyzed. A contrastive analysis about the phase, structure and micro morphology of the products were studied at different reaction time, reaction temperature and different fill rate. Improve the hydrothermal system temperature, filling rate and prolonging the reaction time is beneficial to the formation of VO2. Product formation in hydrothermal system has experienced the solvation effect, hydrolysis, condensation, oxidation and reduction reaction, dehydration reaction and acid hydrolysis of vanadium complexes (NH4)5(VO)6(CO3)4(OH)9(H2O). High reaction temperature and the filling rate can promote the redox reaction and acid hydrolysis of vanadyl complexes, and improve the degree of crystallization of VO2. VO2 nanosheets formed through Ostwald ripening incomplete growth, crystal face fierce competition dynamic balance, collide and strong friction with each other.