N-doped nanoporous Co3O4 nanosheets with oxygen vacancies as oxygen evolving electrocatalysts.

Developing highly active electrocatalysts for the oxygen evolution reaction (OER) with a high surface area, high catalytic activity, low cost and high conductivity is a big challenge for various energy technologies. Herein, for the first time, we realized the simultaneous nitrogen doping and etching of Co3O4 nanosheets to produce N-doped nanoporous Co3O4 nanosheets with oxygen vacancies by N2 plasma. The increase in active sites in N-doped Co3O4 nanosheets and improved electronic conductivity with N doping and oxygen vacancies results in excellent electrocatalytic activity for the OER. Compared with pristine Co3O4 nanosheets, the N-doped Co3O4 nanosheets with oxygen vacancies have a much lower required potential of 1.54 V versus a reversible hydrogen electrode than the pristine Co3O4 nanosheets (1.79 V) to reach the current density of 10 mA cm-2. The N-doped and etched Co3O4 nanosheets have a much lower Tafel slope of 59 mV dec-1 than pristine Co3O4 nanosheets (234 mV dec-1). The enhanced electrocatalytic activity for the OER is caused by the increased surface area, N doping and the produced oxygen vacancies.