Experimental and DFT Study of Electrochemical Promotion of Cu/ZnO Catalysts for the Reverse Water Gas Shift Reaction

Abstract

This study investigates the use of electrochemical promotion of catalysis (EPOC) toin situ control the catalytic rate of reverse water gas shift (RWGS) reaction that recycles wastefulCO2 into CO. Nanostructured Cu/ZnO catalysts with varying Cu loadings (5, 10, 20, 40, and 60wt.%) are synthesized for RWGS. Compared to unsupported Cu nanoparticles and bare ZnOsupport, Cu/ZnO catalysts exhibit improved performance due to metal support interaction. 20 and40 wt.% Cu/ZnO catalysts show the highest open-circuit catalytic rates (r0) owing to larger specificsurface areas (SBET = 38 m2 g-1). In EPOC experiments, the application of constant currents results in promoted reaction rates, with the highest enhancement ratio (ρ = 1.14) and apparent Faradaicefficiency (Λ = 3.16) observed for 10 wt.% Cu/ZnO. Density functional theory (DFT) computations and physicochemical characterizations support the lattice oxygen provisionmechanism, where oxygen migrates from ZnO to Cu during polarization. This results in partialoxidation of Cu to Cu2O and a subsequent increase in RWGS rate. A correlation between SBET and r0 and a positive relationship between the electrochemical surface area (ECSA) and Λ values inEPOC are identified, indicating that electrochemically active sites are important for catalyst activation under polarization.