Single-Atom-Layer-Induced Reversed Diffusion Pathway of Reactive Metal–Support Interaction

Reactive metal-support interaction (RMSI) exhibits great potential in modulating the component, configuration, and electronic structure of supported metal catalysts. While current experimental and theoretical studies both regard that RMSI occurs through one-step diffusion of metal atoms from the support toward the supported nanoparticles, our study reveals a reversed diffusion pathway during RMSI, where Pt atoms in the supported nanoparticles spread out on the support to form a single-atom-layer Pt before the incorporation of Ti elements from the support in Pt/TiO₂. The single-atom-layer Pt, identified by in situ heating aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), could weaken Ti-O bonds through electron transfer, facilitate surface oxygen release and following Ti atom migration toward Pt, ultimately enabling intermetallic compound (IMC) formation. The elucidated formation mechanism with a single-atom-layer Pt offers guidance for reducing the diffusion energy barrier of metal atoms within the support to ensure the effective formation of an IMC. The resulting Pt₃Ti IMC, featuring electron-rich Pt active sites with a downshifted d-band center, exhibits exceptional resistance to CO poisoning during electrocatalytic hydrogen oxidation.