Electrochemical carbon dioxide reduction reaction (CO₂RR) powered by renewable electricity offers an attractive approach to reduce carbon emission and at the same time produce valuable chemicals/fuels. To design efficient CO₂ reduction electrocatalyst, it is important to understand the structure-activity relationship. Herein, we design a series of single Co atoms electrocatalysts with well-defined active sites electronic structures, which exhibit outstanding CO₂RR activity with controllable selectivity to CO. Experimental and density functional theory (DFT) calculation studies show that introducing nitro (amino) ligand next to single Co atom catalytic center with electron-withdrawing (electron-donating) capability favors (hinders) CO₂ reduction catalysis. This work provides an in-depth understanding of how functional ligand affects the splitting of transition metal 3d electron orbital, thereby changing the electron transfer from transition metal active site to CO₂, which is closely related to the Gibbs free energy of the rate-determining step (CO₂+e⁻+*→*CO₂⁻).

由可再生电力驱动的电化学二氧化碳还原反应（CO ₂ RR）提供了一种有吸引力的方法来减少碳排放，同时生产有价值的化学品/燃料。为了设计有效的CO ₂还原电催化剂，重要的是要了解其结构活性关系。本文中，我们设计了一系列具有明确的活性位电子结构的单Co原子电催化剂，这些催化剂具有出色的CO ₂ RR活性和对CO的选择性可控。实验和密度泛函理论（DFT）计算研究表明，引入硝基（氨基）具单个吸电子（给电子）能力的单个Co原子催化中心旁边的配体有利于（阻碍）CO ₂还原催化。这项工作深入了解了功能配体如何影响过渡金属3d电子轨道的分裂，从而改变了电子从过渡金属活性位到CO _2的转移，这与速率决定的吉布斯自由能密切相关步骤（CO ₂ + E ^- + *→* CO ₂ ^- ）。