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 on Cu mesh (CM) (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.