Synthesis of reduced cubic phase WO 3 − x nanosheet by direct reduction of H 2 WO 4 ·H 2 O

The cubic phase WO3−x with two-dimensional nanosheet structure is prepared at a relative low temperature through thermal decomposition method. The starting material and decomposition environment are the key factors to obtain the cubic phase WO3−x. The cubic crystal structure is stabilized by the large amounts of oxygen vacancies. The dark blue cubic WO3−x exhibits electrocatalysis performance for hydrogen evolution reaction (HER) in acidic solution (an overpotential −294 mV at the current density of 10 mA/cm2). The cubic phase WO3−x shows good photothermal stability with eminent photothermal conversion effect (photothermal conversion efficiency is 48.7% at 808 nm).