Al-Doped Octahedral Cu₂O Nanocrystal for Electrocatalytic CO₂ Reduction to Produce Ethylene

Ethylene is an ideal CO₂ product in an electrocatalytic CO₂ reduction reaction (CO₂RR) with high economic value. This paper synthesised Al-doped octahedral Cu₂O (Al–Cu₂O) nanocrystal by a simple wet chemical method. The selectivity of CO₂RR products was improved by doping Al onto the surface of octahedral Cu₂O. The Al–Cu₂O was used as an efficient electrocatalyst for CO₂RR with selective ethylene production. The Al–Cu₂O exhibited a high % Faradic efficiency (FE_C2H4) of 44.9% at −1.23 V (vs. RHE) in CO₂ saturated 0.1 M KHCO₃ electrolyte. Charge transfer from the Al atom to the Cu atom occurs after Al doping in Cu₂O, optimizing the electronic structure and facilitating CO₂RR to ethylene production. The DFT calculation showed that the Al–Cu₂O catalyst could effectively reduce the adsorption energy of the *CHCOH intermediate and promote the mass transfer of charges, thus improving the FE_C2H4. After Al doping into Cu₂O, the center of d orbitals shift positively, which makes the d–band closer to the Fermi level. Furthermore, the density of electronic states increases due to the interaction between Cu atoms and intermediates, thus accelerating the electrochemical CO₂ reduction process. This work proved that the metal doping strategy can effectively improve the catalytic properties of Cu₂O, thus providing a useful way for CO₂ cycling and green production of C₂H₄.