Restructuring Ni/Al2O3 by addition of Ga to shift product selectivity in CO2 hydrogenation: The role of hydroxyl groups

•Ni-Ga on alumina shows high selectivity for CO in the RWGS reaction at 400 °C.•Addition of Ga results in improved dispersion of Ni on the support.•OH groups play a prominent role for the catalyst activity.•The reaction proceeds through bicarbonates and formates as intermediate products. Ni/Al2O3 is an active catalysts for CO2 hydrogenation to both CH4 and CO. By doping with Ga, we succeeded in shifting the selectivity of these catalysts almost completely toward CO. In-situ IR spectroscopy studies showed that the catalyst activity is directly related to the concentration of surface hydroxyl groups that are responsible for the adsorption of CO2 and the formation of intermediate bicarbonates and formates on the catalyst surface. The addition of Ga improved the Ni dispersion which was concomitant with the formation of a Ni-Ga layer on the surface of alumina, thereby reducing the surface hydroxyl concentration. The reduced and weakened interaction between the intermediate products, i.e. bicarbonates and formates, and the catalyst surface, increased the CO selectivity from ∼40 % to 98 %.