Atomic-level environment engineering in carbon-based single-atom catalysts: a review of theoretical insights for hydrogen evolution and triiodide reduction

Carbon-based materials have emerged as ideal platforms for designing single-atom catalysts (SACs) owing to their tunable atomic-scale microenvironments, superior electrical conductivity, and distinctive charge-transfer properties. The precise engineering of these atomic-level environments plays a crucial role in determining both the electronic structure and catalytic performance of carbon-based SACs. However, the fundamental mechanisms governing single-atom bonding configurations and their influence on catalytic reactivity remain unexplored. This review systematically summarizes recent theoretical advances in modulating SAC activity via defect engineering, heteroatom doping, metal–metal interactions, nanocluster effects, and the design of tailored coordination compounds. By establishing robust structure–activity relationships, we provide critical theoretical insights into the rational design of high-performance SACs for sustainable hydrogen production and solar energy conversion. In addition, we identify key challenges and outline future research avenues to advance SACs as viable solutions for sustainable clean energy technologies. This review not only enhances the fundamental understanding of SACs, but also lays the foundation for the development of next-generation catalysts for energy-related applications.