Synthesis of hexagonal WO3 nanowires by microwave-assisted hydrothermal method and their electrocatalytic activities for hydrogen evolution reaction

Hexagonal WO3 (hex-WO3) nanowires with high aspect ratio and crystallinity have been prepared for the first time by a microwave-assisted hydrothermal method. By using X-ray diffraction, scanning electron microscopy,transmission electron microscopy and high resolution transmission electron microscopy, the phase and morphology of the products were identified, which were controlled by reaction temperature, holding time and added salts. Uniform hex-WO3 nanowires with a diameter of 5-10 nm and lengths of up to several micrometres were synthesized by a microwave-assisted hydrothermal process at 150 degrees C for 3 h in a solution containing (NH4)(2)SO4 as a capping reagent and Na2WO4 as a starting material. The aspect ratio and specific surface area of hex-WO3 nanowires were 625 and 139 m(2) g(-1), respectively, which represented one of the highest values reported for WO3. The electrocatalytic activity for hydrogen evolution reaction of hex-WO3 nanowires was also investigated by cyclic voltammetry and linear sweep voltammetry. The results demonstrated that hex-WO3 nanowires were a promising electrocatalyst for the hydrogen evolution reaction (HER) from water.