Promoting hydrophilic cupric oxide electrochemical carbon dioxide reduction to methanol via interfacial engineering modulation

Insufficient active sites at the hydrophilic grassy CuO electrode tend to produce H2 in electrochemical CO2 reduction reaction. To enhance the intrinsic catalytic activity, a metal-oxide heterogeneous interface was created via interfacial engineering modulation by loading Pd on CuO. The CuO/Pd electrode exhibited excellent electrochemical CO2 reduction performance, with 54% Faraday efficiency at −0.65 V for CH3OH. [Display omitted] •The active site of the grass-like hydrophilic CuO electrode was verified to be oxide-derived Cu by the transition in wettability.•Pd loading on CuO by interfacial engineering both satisfies the reduction of CuO to Cu and also contributes to the increase of active sites.•The interfacial effect between CuO and Pd appreciably reduces the work function of CuO to promote CO2 reduction.•The FE of CH3OH reach up to 54 % at −0.65 V over CuO/Pd-2. Copper-based catalysts have been extensively investigated in electrochemical carbon dioxide (CO2) reduction to promote carbon products generated by requiring multiple electron transfer. However, hydrophilic electrodes are unfavourable for CO2 mass transfer and preferentially hydrogen (H2) evolution in electrochemical CO2 reduction. In this paper, a hydrophilic cupric oxide (CuO) electrode with a grassy morphology was prepared. CuO-derived Cu was confirmed as the active site for electrochemical CO2 reduction through wettability modulation. To enhance the intrinsic catalytic activity, a metal-oxide heterogeneous interface was created by engineering modulation at the interface, involving the loading of palladium (Pd) on CuO (CuO/Pd). Both the electrochemically active area and the electron transfer rate were enhanced by Pd loading, and significantly the reduced work function further facilitated the electron transfer between the electrode surface and the electrolyte. Consequently, the CuO/Pd electrode exhibited excellent excellent performance in electrochemical CO2 reduction, achieving a 54 % Faraday efficiency at −0.65 V for methanol (CH3OH). The metal-oxide interfacial effect potentially improves the intrinsic catalytic activity of hydrophilic CuO electrodes in electrochemical CO2 reduction, providing a conducive pathway for optimizing hydrophilic oxide electrodes in this process.