MgH2/CuxO Hydrogen Storage Composite with Defect-Rich Surfaces for Carbon Dioxide Hydrogenation.

Thermal conversion of CO2 to value-added chemicals is challenging due to the extreme inertness of the CO2 molecule and the low selectivity of products. We reported a defect-rich MgH2/CuxO hydrogen storage composite from mechanochemical ball-milling for the catalytic hydrogenation of CO2 to lower olefins. The defect-rich MgH2/CuxO hydrogen storage composite achieves a C2=-C4= selectivity of 54.8% and a CO2 conversion of 20.7% at 350 °C under a low H2/CO2 ratio of 1:5, which increases the efficiency of H2 utilization by offering lattice H- species for hydrogenation. Density functional theory calculations show that the defective structure of MgH2/CuxO can promote CO2 molecule adsorption and activation, while the electronic structure of MgH2 is beneficial for offering lattice H- for CO2 molecule hydrogenation. The lattice H- can combine the C site of CO2 molecule to promote the formation of Mg formate, which can be further hydrogenated to lower olefins under a low H- concentration. This work for CO2 conversion by a defect-rich MgH2/CuxO hydrogen storage composite can inspire the catalysts design for the hydrogenation of CO2 to lower olefins.