Surface modification of CuO nanoflake with Co3O4 nanowire for oxygen evolution reaction and electrocatalytic reduction of CO2 in water to syngas

Transition metal oxides with hierarchical structures that grow on conductive substrates directly, which have been considered as promising catalysts for electrochemical catalysis. In this study, we used a stepwise synthesis method to prepare CuO nanoflake @Co3O4 nanowire composite nano-arrays (denote as CuO/Co3O4 composite), which show an excellent electrochemical performance. In the oxygen evolution reaction (OER), the CuO/Co3O4 composite shows lower overpotential of 450 mV at the current density of 50 mA cm−2 and a smaller Tafel slope of 42 mV dec−1 in KOH solution (1 M, pH = 13.7). In the electrocatalytic CO2 reduction reaction, the prepared CuO/Co3O4 composite showed better CO selectivity in KHCO3 aqueous solution (0.1 M, CO2 saturated), the corresponding Faradaic efficiency of CO product reached 35.4%, and the product ratio of H2 to CO was controlled by changing the potential values. The synthesis strategy reported here opens a way for designing high-performance electrodes for electrochemical catalysis and also provides new ideas for the construction of overall reaction (CO2 + H2O → CO + O2).