Stabilizing mechanism of single-atom catalysts on a defective carbon surface

Single-atom (SA) catalysts represent the ultimate limit of atom use efficiency for catalysis. Promising experimental progress in synthesizing SA catalysts aside, the atomic-scale transformation mechanism from metal nanoparticles (NPs) to metal SAs and the stabilization mechanism of SA catalysts at high temperature remain elusive. Through systematic molecular dynamics simulations, for the first time, we reveal the atomic-scale mechanisms associated with the transformation of a metal NP into an array of stable SAs on a defective carbon surface at a high temperature, using Au as a model material. Simulations reveal the pivotal role of defects in the carbon surface in trapping and stabilizing the Au-SAs at high temperatures, which well explain previous experimental observations. Furthermore, reactive simulations demonstrate that the thermally stable Au-SAs exhibit much better catalyst activity than Au-NPs for the methane oxidation at high temperatures, in which the substantially reduced energy barriers for oxidation reaction steps are the key. Findings in this study offer mechanistic and quantitative guidance for material selection and optimal synthesis conditions to stabilize metal SA catalysts at high temperatures.