Trade-Off between the Coordination Environment and Active-Site Density on Fe–N x C y –C Catalysts for Enhanced Electrochemical CO 2 Reduction to CO

作者：Jing Wang, Yangyang Song, Chen Chen, Xian Zhao, Weiliu Fan · 发表于：ACS Catalysis · 年份：2023 · DOI：10.1021/acscatal.3c04976 · 被引用次数：56 · 研究领域：CO2 Reduction Techniques and Catalysts、Electrocatalysts for Energy Conversion、Catalytic Processes in Materials Science

Coordination environment and active site density are the two factors that affect the performance of single-atom catalysts (SACs). Herein, we performed systemic density functional theory calculations on the CO 2 reduction reaction (CO 2 RR) catalyzed by a series of Fe–N x C y –C ( x = 2–4, y = 0–2) SACs to shed light on this issue. It is found that the maximum free-energy change (Δ G max ) step depended on the coordination environment. When Fe was fourfold-coordinated, the hydrogenation of CO 2 to *COOH was the Δ G max step, involving proton-coupled electron transfer (PCET; Δ G max,PCET ). When Fe was threefold-coordinated, the *CO desorption process was the Δ G max step, which was without PCET (Δ G max,nPCET ). Notably, Δ G max,PCET was negatively correlated with Δ G max,nPCET . Moreover, the Fe site density affected the catalytic activity, which required a balance between the coordination environment and density. The orbital hybridization between the 3 d z 2 and 3 d xz (3 d yz ) orbitals of Fe atom and the intermediates *COOH-π 1 * or *CO-2π*, which is strongly related to the spin characteristics of Fe sites, can promote this process. Accordingly, based on the magnetic moment, electronegativity, and catalytic site density of catalytic systems, a comprehensive descriptor (φ) that can evaluate the binding stabilities and reactivities of different intermediates during CO 2 RR was proposed. Using φ, we validated three strategies for screening catalysts: nearest and subnearest co...