CeNCl-CeO₂ Heterojunction-Modified Ni Catalysts for Efficient Electroreduction of CO₂ to CO

Renewable-electricity-powered electrochemical CO2 reduction (CO2RR) is considered one of the most promising ways to convert exhaust CO2 into value-added chemicals and fuels. Among various CO2RR products, CO is of great significance since it can be directly used as feedstock to produce chemical products through the Fischer-Tropsch process. However, the CO2-to-CO electrocatalytic process is often accompanied by a kinetically competing side reaction: H-2 evolution reaction (HER). Designing electrocatalysts with tunable electronic structures is an attractive strategy to enhance CO selectivity. In this work, a CeNCl-CeO2 heterojunction-modified Ni catalyst is successfully synthesized with high CO2RR catalytic performance by the impregnation-calcination method. Benefiting from the strong electron interaction between the CeNCl-CeO2 heterojunction and Ni nanoparticles (NPs), the catalytic performance is greatly improved. Maximal CO Faradaic efficiency (FE) is up to 90% at -0.8 V (vs RHE), plus good stability close to 12 h. Detailed electrochemical tests and density functional theory (DFT) calculation results reveal that the introduction of the CeNCl-CeO2 heterojunction tunes the electronic structure of Ni NPs. The positively charged Ni center leads to an enhanced local electronic structure, thus promoting the activation of CO2 and the adsorption of *COOH.