Theoretical Insights into H<sub>2</sub> Activation and Hydrogen Spillover on Near-Surface Alloys with Embedded Single Pt Atoms
Zhenghui Tan, Jun Chen, Sen Lin
Abstract
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 H 2 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) (Pt 1 -X/Cu(111)) can generally promote the initial hydrogen spillover but suppress the H 2 dissociation process, showing an intractable trade-off effect. While the DFT-calculated H 2 dissociation barrier on Pt 1 -Co/Cu(111) is higher than that on Pt 1 -Ni/Cu(111), the AIMD results show that the H 2 dissociation probability on the Pt 1 -Co/Cu(111) surface is much higher than that on Pt 1 -Ni/Cu(111). The trajectory analysis shows that H 2 molecules on Pt 1 -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 H 2 dissociation probability compared to the case on Pt 1 -Ni/Cu(111). This work provides a clear picture for understanding the structure–activity relationships of H 2 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.