Theoretical Insights into H₂ Activation and Hydrogen Spillover on Near-Surface Alloys with Embedded Single Pt Atoms

Despite extensive studies of hydrogen spillover on single-atom alloy surfaces, a thorough understanding of the structure–activity relationship is still lacking. Here, we investigate H₂ dissociation and diffusion of the dissociated H species on the near-surface alloys embedded with single Pt atoms using density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. The DFT results indicate that subsurface alloying with early transition metals (X) (Pt₁-X/Cu(111)) can generally promote the initial hydrogen spillover but suppress the H₂ dissociation process, showing an intractable trade-off effect. While the DFT-calculated H₂ dissociation barrier on Pt₁-Co/Cu(111) is higher than that on Pt₁-Ni/Cu(111), the AIMD results show that the H₂ dissociation probability on the Pt₁-Co/Cu(111) surface is much higher than that on Pt₁-Ni/Cu(111). The trajectory analysis shows that H₂ molecules on Pt₁-Co/Cu(111) can adopt a more convenient conformation for dissociation when approaching the so-called close-range physisorption zone (CPZ) due to the relatively flat topography of the potential energy surface, thus increasing the H₂ dissociation probability compared to the case on Pt₁-Ni/Cu(111). This work provides a clear picture for understanding the structure–activity relationships of H₂ activation and hydrogen spillover over single-atom catalysts. More importantly, it highlights an overlooked but essential role of the dynamic orientation of the reactant in heterogeneous catalysis.