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 @Co 3 O 4 nanowire composite nano-arrays (denote as CuO/Co 3 O 4 composite), which show an excellent electrochemical performance. In the oxygen evolution reaction (OER), the CuO/Co 3 O 4 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 CO 2 reduction reaction, the prepared CuO/Co 3 O 4 composite showed better CO selectivity in KHCO 3 aqueous solution (0.1 M, CO 2 saturated), the corresponding Faradaic efficiency of CO product reached 35.4%, and the product ratio of H 2 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 (CO 2  + H 2 O → CO + O 2 ).