Metallic WO2-Carbon Mesoporous Nanowires as Highly Efficient Electrocatalysts for Hydrogen Evolution Reaction

The development of electrocatalysts to generate hydrogen, with good activity and stability, is a great challenge in the fields of chemistry and energy. Here we demonstrate a "hitting three birds with one stone" method to synthesize less toxic metallic WO2-carbon mesoporous nanowires with high concentration of oxygen vacancies (OVs) via calcination of inorganic/organic WO3-ethylenediamine hybrid precursors. The products exhibit excellent performance for H2 generation: the onset overpotential is only 35 mV, the required overpotentials for 10 and 20 mA/cm(2) are 58 and 78 mV, the Tafel slope is 46 mV/decade, the exchange current density is 0.64 mA/cm(2), and the stability is over 10 h. Further studies, in combination with density functional theory, demonstrate that the unusual electronic structure and the large amount of active sites, generated by the high concentration of OVs, as well as the closely attached carbon materials, were key factors for excellent performance. Our results experimentally and theoretically establish metallic transition metal oxides (TMOs) as intriguing novel electrocatalysts for H2 generation. Such TMOs with OVs might be promising candidates for other energy storage and conversion applications.