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 alpha-MoC(100) supported typical platinum group metal (PGM) single atoms (Rh-1, Pd-1, and Pt-1) and Au-1 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 Rh-1, Pd-1, and Pt-1 can serve as single-atom promoters (SAPs) to improve the WGS performance of surface Mo atoms on alpha-MoC(100). The enhanced activity originates from the fact that SAP modifies the electronic structure of Mo active sites. Comparatively, the Au-1 species not only acts as an SAP but also directly participates in the catalysis as a single-atom player. The additional experiments with singleatom 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.