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.