A Review on Single Site Catalysts for Electrochemical CO₂ Reduction

Single site catalysts (SSCs), characterized by high atomic utilization and well-defined active sites, exhibit significant potential in the field of CO₂ electroreduction (CO₂RR). Typically, SSCs tend to exhibit a 2-electron transfer reaction in CO₂RR, and there remain significant challenges in achieving efficient conversion above 2-electrons (methane (CH₄) and multicarbon products(C₂₊). Therefore, a systematic review is crucial to summarize the recent advancements in single site CO₂ electrocatalysts and their structure-activity relationship. The discussion begins with the state-of-the-art characterization techniques of SSCs. Then the influence of central atoms, coordination environments, support and metal-support interactions on catalytic performance of SSCs is discussed in detail. Subsequently, the regulation strategies to improve the activity and selectivity of CH₄ and C₂₊ products are discussed. Furthermore, the dynamic evolution of metal active sites and the true nature of active sites during CO₂RR are also addressed. Finally, the challenges associated with the utilization of SSCs in CO₂RR for CH₄ and C₂₊ product formation are analyzed.