Insight into Electrochemical Promotion of Cu/Co₃O₄ Catalysts for the Reverse Water Gas Shift Reaction

Abstract

In this study, Copper-modified Co 3 O 4 (Cu/Co 3 O 4 ) catalysts were investigated for the reverse water gas shift (RWGS) reaction at 200-400 °C under different CO 2 : H 2 ratios. It was found that the electrocatalytic performance of Co 3 O 4 was improved by loading 4 weight percent (wt.%) Cu nanoparticles (average size: 13 nm), which could be then used as an electrode in electrochemical promotion of catalysis (EPOC) studies. Under the applied voltages of + 2 V and À 1 V, the catalytic rates were suppressed and increased by about 40 % and 14 %, respectively. This was due to the changes in the active oxidation states of Cu and Co caused by O 2À migration under polarization, as confirmed by XPS, XRD, and cyclic voltammetry (CV). The study also revealed that the exchange current density (i 0 ) was counter-correlated with the open-circuit catalytic rate (r 0 ) and could serve as an informative tool for predicting the catalytic rate, which was demonstrated for the first time in the instance of RWGS reaction.

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

“…Despite the formation of Cu 2+ , Cu 0 and Cu 1+ were still the main phases after the reactions due to the protection of ZnO support. The XPS spectra of O 1s for as-prepared ZnO, 10CuZnO, and 60CuZnO are compared in Figure c, with lattice O 2– (O L , represents Zn–O bonding) of ZnO found at 530 eV, defect O 2– (O V , represents oxygen-deficient region) of ZnO observed at 531 eV, and adsorbed oxygen (−OH) located at 532 eV. , It was found that by increasing Cu content from 0 to 60 wt %, the O L increased from 44.19 to 64.23% and the O V decreased from 48.58 to 21.47%. Moreover, the O L peak position shifted from 530.25 to 530.8 eV.…”

“…CV is commonly applied to the catalyst-working electrode to investigate the redox properties of materials and provide in situ information about the electrochemical processes and changes in the oxidation states, and thus is widely used in EPOC studies as an electrochemical characterization method. ,, Figure a,b shows the CVs of as-prepared Cu/ZnO catalysts deposited on YSZ in argon at 400 °C. The CVs cycled from −0.8 to 1.5 V and then back to −0.8 V at a scan rate of 20 mV s –1 , where the anodic cycle involved electro-oxidation and the cathodic cycle involved electro-reduction.…”

“…Also, the combination of MSI and EPOC can further modify the electrocatalytic performance. For instance, previous studies on Fe/Co 3 O 4 17 and Cu/Co 3 O 4 18 revealed that the MSI effect changed the catalytic activity and altered the EPOC behavior. This provides an opportunity for EPOC studies over catalysts with multiple phases for the RWGS reaction.…”