α-MoC Supported Noble Metal Catalysts for Water-Gas Shift Reaction: Single-Atom Promoter or Single-Atom Player.

In this work, we study the water-gas shift (WGS) reaction catalyzed by α-MoC(100) supported typical platinum group metal (PGM) single atoms (Rh1, Pd1, and Pt1) and Au1 via density functional theory calculations. The adsorption energies of key reaction intermediates and the kinetic barriers of the proposed rate-determining step in the WGS were systematically investigated. It is found that Rh1, Pd1, and Pt1 can serve as single-atom promoters (SAPs) to improve the WGS performance of surface Mo atoms on α-MoC(100). The enhanced activity originates from the fact that SAP modifies the electronic structure of Mo active sites. Comparatively, the Au1 species not only acts as an SAP but also directly participates in the catalysis as a single-atom player. The additional experiments with single-atom catalyst performance and kinetic studies confirm the theoretical calculation conclusions. This study can provide a basis to further develop efficient WGS catalysts by tuning the activity of the substrate with intercalation of SAPs.