Oxygen vacancy rich tungsten oxide with nitrogen doped mesoporous carbon as matrix for overall water splitting and 4-nitrophenol reductive removal

A nitrogen doped mesoporous carbon matrix supported oxygen vacancies rich tungsten oxide composite material, WO3-x@NC (1 > x > 0), has been fabricated successfully with chitosan and H3PW12O40 as precursors through calcination. In this composite material, WO3-x particles with the size about 10–15 nm disperse evenly in nitrogen doped mesoporous carbon matrix. WO3-x@NC presents low overpotentials (η10) of 61 and 306 mV to reach a current density of 10 mA/cm2 for HER and OER in 1.0 M KOH, respectively. With WO3-x@NC as both cathode and anode at the same time, an electrolyzer, WO3-x@NC//WO3-x@NC was constructed for overall water splitting, which only needs a cell voltage of 1.60 V to achieve a current of 10 mA/cm2. During this process, WO3-x@NC//WO3-x@NC exhibits remarkable stability in 48 h. Moreover, besides HER and OER, WO3-x@NC also shows striking catalytic activity for reductive conversion of 4-nitrophenol to 4-aminophenol. Oxygen vacancies from WO3-x and good electron transportation property of nitrogen doped carbon matrix play important roles in overall water electrocatalytic splitting and 4-nitrophenol reductive removal. We expect WO3-x@NC will find its way as a new resource for hydrogen energy as well as a promising material in 4-nitrophenol removal from water.