Defect engineering of high-loading single-atom catalysts for electrochemical carbon dioxide reduction

Electrochemical carbon dioxide reduction reaction (CO₂RR) provides an attractive approach to carbon capture and utilization for the production high-value-added products. However, CO₂RR still suffers from poor selectivity and low current density due to its sluggish kinetics and multitudinous reaction pathways. Single-atom catalysts (SACs) demonstrate outstanding activity, excellent selectivity, and remarkable atom utilization efficiency, which give impetus to the search for electrocatalytic processes aiming at high selectivity. There appears significant activity in the development of efficient SACs for CO₂RR, while the density of the atomic sites remains a considerable barrier to be overcome. To construct high-metal-loading SACs, aggregation must be prevented, and thus novel strategies are required. The key to creating high-density atomically dispersed sites is designing enough anchoring sites, normally defects, to stabilize the highly mobile separated metal atoms. In this review, we summarized the advances in developing high-loading SACs through defect engineering, with a focus on the synthesis strategies to achieve high atomic site loading. Finally, the future opportunities and challenges for CO₂RR in the area of high-loading single-atom electrocatalysts are also discussed.