Cu/MgO Reverse Water Gas Shift Catalyst with Unique CO₂ Adsorption Behaviors

Activation of inert CO₂ molecules for the reverse water gas shift (RWGS) reaction is tackled by incorporating magnesium oxide as a support material for copper, forming a Cu/MgO supported catalyst. The RWGS performance is greatly improved when compared with pure Cu or carbon supported Cu (Cu/C). Operating under a weight hourly space velocity (WHSV) of 300,000 mL ⋅ g^-1 ⋅ h^-1, the Cu/MgO catalyst demonstrates high activity, maintaining over 70 % equilibrium conversion and nearly 100 % CO selectivity in a temperature range of 300-600 °C. In contrast, both Cu/C and commercial Cu, even at ten-times lower WHSV, can only achieve up to 40 % of the equilibrium conversion and quickly deactivated due to sintering. Based on the studies of in-situ temperature resolved infrared spectroscopy and temperature programmed desorption, the improved RWGS performance is attributed to the unique adsorption behavior of CO₂ on Cu/MgO. Density functional theory studies provides a plausible explanation from a surface reaction perspective and reveals the spill-over property of CO₂ from MgO to Cu being critical.