(658d) Reverse Water Gas Shift Reaction of Transition Metal-Promoted Cu/Metal Oxide Catalyst for Enhancing Reaction Rate

A novel transition metal-promoted Cu/metal oxide catalyst has been developed for the reverse water-gas shift (rWGS) reaction under low-temperature conditions. Because the rWGS reaction (CO₂ + H₂ ↔ CO + H₂O, ΔH⁰ = 42.1 kJ mol^-1) is a highly promising method for CO₂ utilization with its high selectivity towards CO at low operating pressure, the produced syngas goes through the Fischer-Tropsch (F-T) synthesis process to produce various value-added chemicals. On the other hand, high operating temperatures for rWGS by the endothermic nature result in limiting the practical applicability of rWGS catalysts. Then, various approaches have been attempted to lower the working temperature of the rWGS reaction by enhancing the reaction rate.

Herein, the transition metal-promoted Cu/metal oxide catalyst was synthesized using the sol-gel combustion method. The resulting catalyst exhibited a high CO₂ to CO conversion rate of up to 13% even at low rWGS working temperatures (250℃), which is near its theoretical CO₂ to CO conversion rate of 16%. Moreover, the catalyst displayed an unprecedentedly high reaction rate of 229.0 _μmol∙g_cat^-1∙s^-1 at 400℃.

Several experiments including H₂-temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS), and in-situ diffuse reflectance infrared Fourier-transform (DRIFTS) were conducted to investigate the synergistic effect of the transition metal promoter, in interaction with Cu/metal oxide catalyst. Based on the analysis of the H₂-TPR and XPS data, the role of the transition metal promoter onto the Cu/metal oxide catalyst was clarified. The rate-determining step (RDS) and reaction mechanism of the rWGS reaction were also elucidated through DRIFTS spectra analysis.

The findings will provide essential insights into optimal catalyst design criteria that can improve not only the rWGS reaction rate but also other CO₂ conversion reactions.