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) to in situ control the catalytic rate of the reverse water gas shift (RWGS) reaction that recycles wasteful CO 2 into CO. Nanostructured Cu/ZnO catalysts with varying Cu loadings (5, 10, 20, 40, and 60 wt %) are synthesized for RWGS. Compared to unsupported Cu nanoparticles and bare ZnO support, Cu/ ZnO catalysts exhibit improved performance due to metal−support interaction. 20 and 40 wt % Cu/ZnO catalysts show the highest open-circuit catalytic rates (r 0 ) owing to larger specific surface areas (S BET = 38 m 2 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 Faradaic efficiency (Λ = 3.16) observed for 10 wt % Cu/ZnO. Density functional theory (DFT) computations and physicochemical characterizations support the lattice oxygen provision mechanism, where oxygen migrates from ZnO to Cu during polarization. This results in partial oxidation of Cu to Cu 2 O and a subsequent increase in RWGS rate. A correlation between S BET and r 0 and a positive relationship between the electrochemical surface area (ECSA) and Λ values in EPOC are identified, indicating that electrochemically active sites are important for catalyst activation under polarization.