Why Does Single-Atom Photocatalysis Work Better Than Conventional Photocatalysis? A Study on Ultrafast Excited Carrier and Structure Dynamics.

With the introduction of single atoms in photocatalysis, a small change in the electronic and geometric structure of the substrate can result in higher energy conversion efficiency, whereas the underlying microscopic dynamics are rarely illustrated. Here, employing real-time time-dependent density functional theory, we explore the ultrafast electronic and structural dynamics of single-atom photocatalysts (SAPCs) in water splitting at the microscopic scale. The results demonstrate that a single-atom Pt loaded on graphitic carbon nitride greatly promotes photogenerated carriers compared to traditional photocatalysts, and effectively separates the excited electrons from holes, prolonging the lifetime of the excited carriers. The flexible oxidation state (Pt 2+ , Pt 0 , or Pt 3+ ) renders the single atom as an active site to adsorb the reactant and to catalyze the reactions as a charge transfer bridge at different stages during the photoreaction process. Our results offer deep insights into the single-atom photocatalytic reactions and benefit the design of high-efficiency SAPCs.