Engineering vacancy and hydrophobicity of spherical coral-like CuO catalyst for effective electrochemical CO₂ reduction to ethylene

Electrochemical carbon dioxide reduction (ECR) to ethylene by using renewable energy is a viable way to tackle the global climate change, and beneficial to facilitate closing the carbon cycle. Herein, a sulfur-doped spherical coral-like CuO (S-CuO) catalyst was facile synthesized, which is enabling efficient conversion CO2-to-C2H4. The obtained 5% S-CuO can reach the Faradaic efficiency (C2H4) of 48.4% with a current density of 15 mA cm(-2) at-1.3 V vs. RHE, which maintained stability over 20 h in 0.1 M KHCO3 electrolyte. XPS, SEM, TEM, and XRD were applied in the characterization of the materials. EPR, CO2 adsorption measurements and density functional theory calculations results indicate that the incorporation of S can promote CO2 adsorption, activation and the formation of *COOH intermediate, which is boosting CO2 conversion enabling the high selectivity to C2H4. Compared to unmodified CuO, electrocatalytic studies show that the greatly increased C2H4 activity on S-CuO is because of the fast electron transfer. Meanwhile, the contact angle measurement reveals the excellent selectivity is derived from the suppression of the hydrogen evolution reaction after the S doping.