Engineering α-MoC1–x through Gradient Si/Al Ratios of Zeolite Supports for Efficient Water–Gas Shift Reaction

Pt/α-MoC catalysts, synthesized by supporting platinum on α-phase molybdenum carbide (α-MoC), have emerged as promising candidates for the low-temperature water–gas shift reaction (WGSR) due to their high catalytic activity. However, their performance is often limited by insufficient density of active Pt–Mo interfacial sites and inadequate stability under reaction conditions. In this study, a ternary Pt/α-MoC/MFI catalyst was constructed by incorporating MFI-type zeolites with varying Si/Al ratios as a support component. Comprehensive characterization revealed that modulating the Si/Al ratio of the zeolite support alters the carburization process, with silica-rich supports promoting the formation of a more optimal molybdenum carbide structure and effectively suppressing carbon deposition during reaction. In addition, the use of high-silica supports increased the number of active Pt–Mo interfacial sites and enhanced key steps such as water dissociation and –OH group conversion. Consequently, the Pt/α-MoC/S-1 catalyst─synthesized using purely siliceous S-1 zeolite as the support─exhibited the highest intrinsic activity of 7.4 molCO/molPt/s at 523 K, outperforming all other zeolite-supported Pt/α-MoC catalysts as well as the bulk Pt/α-MoC catalyst.