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

Catalytic reverse water gas shift (RWGS) reaction has been regarded as an attractive route for the conversion of waste CO2 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/SiO2 catalysts modified by WOx have been prepared to tune the WOx/Pt interfacial site for enhancing the RWGS reaction. Characterizations revealed the coverage of Pt particles by WOx clusters (polytungstate with a low polymerization degree) with an electron transfer from Pt to WOx. As a result, new WOx/Pt interfacial sites are created at the expense of surface-accessible Pt sites, which weaken CO adsorption while enhancing CO2 adsorption and activation at the interface. The intrinsic reaction rate and turnover frequency on Pt-W/SiO2 with an optimal W loading (0.5 wt %) are similar to 8 and similar to 12 times higher than those on Pt/SiO2 at 400 degrees C, with a 100% CO selectivity, pointing to an optimal WOx/Pt interfacial sites resulting from optimal coverage of Pt by WOx. 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 WOx/Pt. The interfacial sites of WOx/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.