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

Homogeneous NaBH 4 -reduced Co 3 O 4 thin film electrodes with enhanced oxygen evolution electrocatalysis were obtained via a controlled-synthesis route. Firstly CoO x colloids were synthesized via ethylene glycol solvothermal method and cast on conductive glass substrates. The oxygen evolution reaction (OER) electrocatalysis of these as-prepared Co 3 O 4 thin films were then significantly enhanced via a simple surface reduction by NaBH 4 solution. The OER catalytic performance of the NaBH 4 -reduced thin films was strongly dependent on the NaBH 4 concentration. The use of NaBH 4 -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, 20 -Co 3 O 4 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 B 12.5, 20 -Co 3 O 4 thin film electrodes possessed good stability that can well recover its OER performance in a 24-h chronoamperometric stability test.