Recent Progress in and Future Perspectives on High-Density Single-Atom Electrocatalysts

Abstract Single-atom catalysts (SACs) exhibit tremendous potential in electrocatalysis because of their high intrinsic activity and remarkable selectivity arising from their tunable electronic structures and maximal atom utilization. A high density of SACs is fundamental for enhancing the activity and durability during electrochemical reactions. In this review, we first summarize the leading strategies for the synthesis of metal single-atom electrocatalysts and the use of machine learning in the design and screening of SACs, with a focus on maximizing the metal loading through deliberate temperature control, followed by the application of such high-loading SACs to a range of important reactions in electrochemical energy technologies, such as the oxygen reduction reaction (ORR), H 2 O 2 electrosynthesis, the oxygen evolution reaction (OER), the hydrogen evolution reaction (HER), the carbon dioxide reduction reaction (CO 2 RR), the nitrate reduction reaction (NO 3 RR), and the reactions in lithium-sulfur batteries. The review concludes with a perspective highlighting the key challenges and future research directions in the development and application of high-density SACs. Graphical Abstract High-density metal sites are crucial for enhancing the performance of single-atom catalysts (SACs) during electrocatalytic reactions. This review systematically summarizes the principal synthesis strategies for high-density SACs, outlines the application of machine learning-assisted designing and screening SACs, and discusses their applications in electrocatalytic energy storage and conversion systems.