Ultrafast Electron Dynamics Revealing the Synergy between Coordination, Charge Transfer, and Oxidation States in Single-Atom Catalysts

Identifying and understanding active sites in single-atom catalysts (SACs) remains a fundamental challenge, particularly under working conditions. Here, taking platinum (Pt) single atoms loaded on graphitic carbon nitride as a prototypical SAC model, we track the ultrafast electronic and structural dynamics with three different initial coordination environments via real-time time-dependent density functional theory. Our results demonstrate that single Pt atoms coordinated with three nitrogen atoms form a highly photoactive center, significantly enhancing light absorption and promoting efficient spatial separation of photogenerated carriers. Notably, compared to other environments, the critical interplay between the dynamic evolution of local atomic configurations and oxidation state of Pt during the reaction synergistically enhances the catalytic activity of single atoms, that is, stimulating an effective charge transfer to the antibonding orbital of the adsorbate molecule and ultimately leading to successive water splitting. These findings provide microscopic mechanistic insights into the working state of active sites and offer valuable guidance for rational design of SACs.