Homogeneous Co3O4 film electrode with enhanced oxygen evolution electrocatalysis via surface reduction

Homogeneous NaBH4-reduced Co3O4 thin film electrodes with enhanced oxygen evolution electrocatalysis were obtained via a controlled-synthesis route. Firstly CoOx colloids were synthesized via ethylene glycol solvothermal method and cast on conductive glass substrates. The oxygen evolution reaction (OER) electrocatalysis of these as-prepared Co3O4 thin films were then significantly enhanced via a simple surface reduction by NaBH4 solution. The OER catalytic performance of the NaBH4-reduced thin films was strongly dependent on the NaBH4 concentration. The use of NaBH4-reduced thin film electrodes for OER in alkaline solution supported higher current density and consequently negative shifts of the onset potential compared to that of the pristine. The optimal B-12.5,B- 20-Co3O4 thin films exhibited excellent OER catalytic performances: At the current density of 10 mA.cm(-2), a low overpotential of 365 mV and a small Tafel slope of 59.0 mV.dec(-1) were observed. In addition, these B12.5, 20-Co3O4 thin film electrodes possessed good stability that can well recover its OER performance in a 24-h chronoamperometric stability test. (C) 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.