High-Loading Single-Atom Catalysts Synthesis and Applications in Electrolysis

High-loading single-atom catalysts (SACs) have recently emerged as a frontier in electrochemical catalysis because of their complete active-site utilization, tunable coordination environment, and atomically defined structure. While it is widely recognized that the single-atomic site in SACs often presents extraordinary catalytic performance, their limited metal content and low active-site density still hinder large-scale implementation in practical electrochemical reactors. Overcoming this limitation requires the development of strategies to achieve high metal loading while preserving atomic dispersion and stability under operational conditions. In this Review, we comprehensively summarize recent advances in the synthesis of high-loading SACs, the state-of-the-art characterization techniques used to probe their atomic and electronic structures, and their applications in advanced electrochemical systems, such as CO2 electrolyzers, fuel cells, and zinc-air batteries. We critically analyze representative breakthroughs that bridge the gap between atomic-scale loading control and commercial-level performance, elucidating the correlations among metal loading, electronic structure modulation, and catalytic activity. Then, we offer perspectives on rational design strategies and emerging opportunities for integrating high-loading SACs into next-generation electrocatalytic reactors, with the aim of accelerating their transition from laboratory research to industrial deployment.