Experimentally unveiling the origin of tunable selectivity for CO2 hydrogenation over Ni-based catalysts

CO2 reduction with green H2 is an attractive way to produce fuels or chemicals. Owing to the complexity of the reaction network of CO2 hydrogenation, various products could be generated. Understanding the origin of CO2 hydrogenation selectivity is critical to rationally design catalysts with high activity and desired selectivity. Here, through a systematic investigation of the size-dependent catalytic performance of Ni-based catalysts, the primary pathway for Ni-catalyzed CO2 hydrogenation, i.e., the reverse water-gas shift (RWGS) followed by H2-assisted CO dissociation and hydrogenation pathway, is experimentally determined. The rate-determining step in the CO2 methanation reaction is identified to be H2-assisted CO dissociation. Therefore, the activation barrier of H2-assisted CO dissociation can be employed as a quantitative descriptor of CH4 selectivity. The identification of an experimental accessible quantitative descriptor sheds light on the rational design of high-efficient heterogeneous catalysts with fine-tuned product selectivity.