Transition metal (Fe, Co, Ni)-doped cuprous oxide nanowire arrays as self-supporting catalysts for electrocatalytic CO2 reduction reaction to ethylene

The transition metal (Fe, Co, Ni)-doped cuprous oxide (Cu2O) nanowire arrays (M-Cu2O@CM, M = Fe, Co, Ni) are successfully synthesized for the electrocatalytic CO2 reduction reaction (CO2RR) to ethylene (C2H4) through the simple calcination and impregnation-exchange methods. Systematic characterizations have demonstrated that the Ni/Co doping in Cu2O@CM is conducive to stabilizing the Cu+ sites due to the electron transfer from Cu2O to Ni/Co, while the Fe doping has the opposite effect. Consequently, they show the different electrocatalytic performances of Ni-Cu2O@CM > Co-Cu2O@CM > Cu2O@CM > Fe-Cu2O@CM for CO2RR to C2H4 in an H-cell. Among them, Ni-Cu2O@CM exhibits the ∼2.0-fold faradaic efficiency for C2H4 (58.2 % vs. 28.7 %) and the ∼2.5-fold current density (−37.6 vs. −15.0 mA·cm−2) at −1.1 V vs. RHE, as compared with Cu2O@CM. Further experiments reveal that during the electrocatalytic CO2RR, the Ni-Cu2O@CM can generate more *CO, which promotes the C–C coupling reaction. The activity of Co-Cu2O@CM is lower than Ni-Cu2O@CM because of the strong adsorption of *COOH, while the Fe-Cu2O@CM even exhibits a lower activity than Cu2O@CM. This work provides an insight into the effect of transition metal-doped Cu2O array on the electrocatalytic CO2RR to C2H4 products.