Tailoring the oxygen vacancies and electronic structures of the hex-WO3 (100) crystal plane with heteroatoms for enhanced hydrogen evolution performance

Due to the difficulty of developing noble materials for large-scale applications, transition metal oxide materials have become popular alternatives for the hydrogen evolution reaction. However, compared to commercial Pt/C, poor conductivity and hydrogen evolution activity are common for transition metal oxides, including WO3(-x)based semiconductors, so it is therefore necessary to ameliorate the electrode self-properties to be suitable for H2 production. Here, different ratios of S(2- )and Ni2+ salts are introduced into hexagonal WO3 and Ni(0.4)WO3(-x)S(x) is prepared successfully after oxygen vacancies and W-O-S and Ni-W-O bonds are formed on the surface of the Ni(0.4)WO3(-x)S(x) nanorods. The X-ray photoelectron, Raman and electrochemical impedance spectroscopy results show that the incorporation of Ni and S atoms can increase the number of oxygen vacancies and the conductivity for hydrogen evolution, simultaneously demonstrating that the W-O-S and Ni-W-O bonds are the main active sites of the Ni(0.4)WO3(-x)S(x )nanorods. Density functional theory calculations further indicate that the & UDelta;GH* of NiWO3-xSx is closer to 20 % commercial Pt/C. The Tafel slope reduces to 87.3 mV/dec when approaching the Volmer-Heyrovsky kinetic mechanism reaction. Finally, the onset potential is 53 mV. The overpotential is 173 mV at 10 mA/cm2, which is 68 % lower compared to hexagonal WO3.