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.