Tuning Interfacial Sites of WO_x/Pt for Enhancing Reverse Water Gas Shift Reaction

Abstract

Catalytic reverse water gas shift (RWGS) reaction has been regarded as an attractive route for the conversion of waste CO 2 to valuable CO. Despite Pt being facile for hydrogenation, the low oxophilicity of Pt renders it less active for RWGS at low temperatures. Herein, Pt/SiO 2 catalysts modified by WO x have been prepared to tune the WO x /Pt interfacial site for enhancing the RWGS reaction. Characterizations revealed the coverage of Pt particles by WO x clusters (polytungstate with a low polymerization degree) with an electron transfer from Pt to WO x . As a result, new WO x /Pt interfacial sites are created at the expense of surface-accessible Pt sites, which weaken CO adsorption while enhancing CO 2 adsorption and activation at the interface. The intrinsic reaction rate and turnover frequency on Pt−W/SiO 2 with an optimal W loading (0.5 wt %) are ∼8 and ∼12 times higher than those on Pt/SiO 2 at 400 °C, with a 100% CO selectivity, pointing to an optimal WO x /Pt interfacial sites resulting from optimal coverage of Pt by WO x . Reaction kinetics, infrared spectroscopy, and density functional theory calculations collectively revealed that the RWGS shifted from the association mechanism via the carboxyl intermediate on bare Pt to the redox mechanism at the interfacial perimeter site of WO x /Pt. The interfacial sites of WO x /Pt enable both C−O breakage and H−O formation, which synergistically enhance the activity. This work demonstrated a simple strategy to tune the metal/oxide interfacial sites, which can apply to other reactions that require multiple functionalities and take place at the metal/oxide interface.