Single Metal Atoms for Energy Storage and Conversion: Recent Advances, Challenges, and Future Perspectives.

Single-atom catalysts (SACs) have recently emerged as a new class of materials that bridge the characteristics of homogeneous and heterogeneous catalysis. Their atomically dispersed metal centers enable nearly complete atomic utilization and high catalytic selectivity. This review highlights recent advances in the synthesis, structure, and functional mechanisms of SACs with a focus on their applications in energy storage and conversion systems. Various preparation strategies, including atomic layer deposition, chemical vapor deposition, and defect-assisted methods, are discussed along with support materials such as metal organic frameworks, carbon-based substrates, and layered oxides. Advanced characterization techniques are summarized to illustrate how coordination environments and electronic structures determine catalytic activity. The review also outlines the use of SACs in electrocatalysis, photocatalysis, and electrochemical energy devices such as lithium-sulfur batteries and supercapacitors. Finally, current limitations such as atom stability, large-scale production, and the need for operando analysis are addressed, providing future directions for the rational design of single-atom catalysts in sustainable energy applications.