Understanding the promotion effect of Pt in the reaction system of water gas shift reaction catalyzed by Pt/α-MoC from theoretical perspectives

Abstract

Pt/α-MoC is an outstanding catalyst for the low-temperature water gas shift (WGS, CO + H2O → H2 + CO2) reaction, exhibiting elevated activity, stability, and selectivity. In this study, three significant active site models (α-MoC-111, Pt-111, and Pt1/α-MoC-111) in Pt/α-MoC catalyst were established to investigate the promotion effect of Pt on the WGS reaction catalyzed by Pt/α-MoC. The results indicate that a synergistic effect at the metal-carbide interface enhances chemical activity compared to pure Pt-111 and α-MoC-111. Firstly, the surface of Pt1/α-MoC-111 exhibits strong metal-support interaction between Pt single atom and α-MoC-111 surface. Compared to the α-MoC-111 surface, the introduction of Pt strengthens the Mo−Mo bond while weakening the Mo−C bond. Secondly, adding a Pt atom significantly increases adsorption strength for CO and H2O, while decreasing it for products (CO2), oxides (O atom), and by-products (C atom). The advantage of suppressing surface carbon deposition and oxidation is observed on the surface of Pt1/α-MoC-111. Furthermore, elementary reactions from the three mainstream reaction pathways of the WGS reaction are systematically calculated to evaluate catalytic performance among these three active sites. On the Pt1/α-MoC-111 surface, activation energy barriers for H2O dissociation and CO oxidation are reduced. This provides theoretical ideas for designing high-efficiency α-MoC based catalysts in the future.