Efficient electrochemical CO2 reduction on a unique chrysanthemum-like Cu nanoflower electrode and direct observation of carbon deposite

•Unique 3D chrysanthemum-like CuO NFs are prepared by in situ pulsed anodic oxidation of Cu foil.•The prepared Cu NFs are able to lower the overpotential of CO2 reduction.•Highly activity towards CO2 reduction is obtained for at least 9 h.•Amorphous carbon deposition on the electrode surface is directly observed for the first time.

The existing Cu-based electrocatalysts for electrochemical reduction of CO2 to chemical commodities suffer instability and large reaction overpotentials. Here we report a novel Cu nanoflower (NF) catalyst with a unique 3D chrysanthemum-like structure. Derived from CuO NFs, the Cu NFs were found to efficiently catalyze the CO2 reduction with 400 mV lower overpotential than polycrystalline Cu. Besides, H2 production was suppressed to be below 25% in terms of Faradaic efficiency in a wide potential window, implying an excellent catalytic selectivity. Prolonged electrolysis showed that the Cu NFs kept a high catalytic activity towards CO2 reduction for over 9 h. In addition, for the first time, the deposition of amorphous carbon on the electrodes after catalysis was directly observed in this study. The reaction pathways of electrocatalytic CO2 reduction and the involvement of the surface carbon in this process were elucidated.