Confinement Effect and Application in Catalytic Oxidation–Reduction Reaction of Confined Single-Atom Catalysts

Single-atom catalysts (SACs) exhibit remarkable 100% atomic economy, making them highly efficient in various fields, including production processes, energy systems, and environmental remediation. However, the migration and agglomeration of single atoms significantly diminish reactivity and increase the operating cost of the catalyst. Due to the size effect, the space confinement effect, and the electron confinement effect, the single atoms are stabilized, and overall catalytic performance is also improved. The confinement effect can be enhanced by modifying the supporting materials with ordered and regular pore structures and improving the binding mode between the support and the single atom. In this Review, the confined functional structure will be explained for the synthesis of confined SACs. It elucidates mechanisms for the formation of the confinement effect and elaborates how the confinement effect improves catalytic performance. This Review is helpful for better understanding, controlling, and utilizing the confinement effect to design confined SACs with impressive catalytic performance.