Synergizing Defect Chemistry and Single‐Atom Catalysis: A Mechanistic Approach Toward Photochemical and Electrochemical CO 2 RR Applications

ABSTRACT In the past few years, a wide array of heterogeneous single‐atom catalysts (SACs) has attracted researchers due to their exceptional performance in CO 2 reduction. However, the role of defects in escalating the catalytic activity of SACs remains enigmatic. Through this review, we aim to provide a detailed understanding of the interplay between defects and catalytic activity in SACs. Despite remarkable advancements, a significant lacuna persists in fully elucidating the dynamic role of defects under operational conditions. This necessitates an integrated experimental and theoretical approach to guide the rational design of next‐generation SACs for CO 2 conversion. Therefore, we aim to account for mechanistic insights into SAC‐led photochemical and electrochemical CO 2 reduction reaction (CO 2 RR) without deviating from our objective of ascertaining the causes behind their catalytic efficiency due to defect engineering. The mechanistic toolkit derived from operando characterizations, density functional theory, and machine learning is provided to correlate defect‐engineered SACs with improved activity and selectivity for CO 2 conversion.