Precise Modulation and Densification of Metal Sites in Single‐Atom Catalysts for Energy Storage and Conversion.

Single‐atom catalysts (SACs) exhibit excellent electrocatalytic performance in various catalytic reactions. However, the low metal loading (<1.0 wt.%) and the difficulty in precisely modulating their coordination configurations hinder the practical yield of target products and the understanding of actual reaction mechanisms. To overcome these obstacles, a series of strategies are proposed to design SACs with a precise coordination configuration and/or a high density of active sites. For an insightful and comprehensive understanding of these strategies, it is worth analyzing and categorizing them according to their intrinsic mechanisms and applicational perspectives. In this review, the synthesis strategies of precise and/or high‐density SACs are first summarized. Moreover, taking typical electrochemical processes, including oxygen reduction reaction, nitrogen reduction reaction, and carbon dioxide reduction reaction, metal–sulfur batteries, etc., as examples, the applications of these SACs are discussed, focusing on their advantages in enhancing the yield of target products, improving the efficiency of energy storage, and revealing the unique effects. Finally, the challenges and perspective of precise modulation and densification of metal sites for SACs are proposed. It is expected that this review can provide a useful reference for the design and preparation of high‐density and/or controllably coordinated SACs. [ABSTRACT FROM AUTHOR]