Modulating Local Coordination in Single-Atom Catalysts: From Fundamental Concepts to Emerging Breakthroughs in Electrocatalysis.

Single-atom catalysts (SACs) have attracted significant interest due to their maximized atom efficiency, structural precision, and unique catalytic properties. While the central metal atom in SACs serves as the primary active site, its catalytic behavior is strongly influenced by the surrounding environment. The local coordination sphere plays a critical role in modulating the electronic structure and reaction pathway, thereby governing the overall activity, selectivity, and stability of SACs. Consequently, precise regulation of this coordination environment through rational engineering strategies is essential for optimizing the performance of SACs. Despite growing interest, comprehensive reviews systematically analyzing local coordination environments and metal-support interactions via electronic descriptors remain scarce, unlike synthesis/application-focused ones. In this review article, we provide an atomic-level, descriptor-driven analysis of coordination effects on the electrocatalytic performance of SACs, emphasizing the synergistic interplay between central metal atoms and their coordination spheres in activating key intermediates in reactions such as water splitting and oxygen/carbon dioxide reduction. We also highlight the unique features of advanced synthetic strategies for SACs, alongside the critical role of spectroscopic and microscopic techniques in elucidating structure-activity relationships, with particular focus on integrating operando investigations and theoretical calculations. Finally, recent advances, remaining challenges, and future opportunities in coordination-regulated SAC electrocatalysis are discussed.