An Overview of Metal Density Effects in Single-Atom Catalysts for Thermal Catalysis

With the development of synthetic methodology, recent breakthroughs have been achieved to prepare metal single-atom catalysts (SACs) with high loadings, leading to an emerging class of SACs called densely populated or high-density SACs. This type of SACs provides not only higher mass-specific activity but also an additional type of interaction among single sites, which can further influence the local geometric and electronic structures of individual metal centers and thus affect the intrinsic activity of active sites. This Review examines the recent research progress of atomic regulation engineering of single-atom density and how it affects the catalytic performance in specific thermal catalysis. Last, we outline the challenges and prospects for future work in the design and development of densely populated SACs.