Tandem Catalysis for Enhanced CO₂ to Ethylene Conversion in Neutral Media

Abstract Selective electrochemical CO₂ reduction reaction (CO₂RR) into value‐added hydrocarbon products such as C₂H₄ provides a sustainable approach to producing carbon chemicals, which however remains a great challenge owing to the multi‐electron transfer process during CO₂ electroreduction. Herein, a tandem catalyst a‐Ni/Cu‐NP@CMK is developed by encapsulating Cu nanoparticles (Cu NPs) into hydrophobic cubic mesoporous carbon with doped atomic Ni‐N₄ moieties. Electrochemical tests demonstrate the outstanding C₂H₄ selectivity of a‐Ni/Cu‐NP@CMK with a high Faraday efficiency (FE) of 72.3% for C₂H₄ at a large current density of 406.1 mA cm⁻² in a flow cell under a neutral medium. Moreover, when used as the cathode catalyst in membrane electrode assembly, a‐Ni/Cu‐NP@CMK stably delivers a current density of 200 mA cm⁻² with a FE_C2H4 of 63% at ‐2.8 V for 30 h, providing a full‐cell energy efficiency of 28.3% for C₂H₄ production. Comparative studies disclose that the hydrophobic microenvironment of the Cu NPs in a‐Ni/Cu‐NP@CMK successfully suppresses the competitive hydrogen evolution reaction and improves the CO₂RR selectivity. Additionally, in situ spectroscopic investigations and theoretical calculations reveal that the efficient CO₂‐to‐CO conversion on the Ni‐N₄ moieties feeds Cu NPs with enriched adsorbed CO (*CO), which facilitates the C─C coupling between adjacent *CO to form C₂H₄.