Rapid Hydrothermal Synthesis of VO2 (B) and Its Conversion to Thermochromic VO2 (M1)

The present study provides a rapid way to obtain VO 2 (B) under economical and environmentally friendly conditions.VO 2 (B) is one of the well-known polymorphs of vanadium dioxide and is a promising cathode material for aqueous lithium ion batteries.VO 2 (B) was successfully synthesized by rapid single-step hydrothermal process using V 2 O 5 and citric acid as precursors.The present study shows that phase-pure VO 2 (B) polytype can be easily obtained at 180 °C for 2 h and 220 °C for 1 h, that is, the lowest combination of temperature and duration reported so far.The obtained VO 2 (B) is characterized by X-ray powder diffraction, high-resolution scanning electron microscopy, and Fourier transform infrared spectroscopy.In addition, we present an indirect way to obtain VO 2 (M1) by annealing VO 2 (B) under vacuum for 1 h.