Nickel Dynamics Switch the Selectivity of CO2 Hydrogenation

The dynamic properties of catalysts under reaction conditions are difficult to characterize and thus their contribution to performance has traditionally been overlooked. Herein, we uncover the mechanism behind the selectivity switch in the hydrogenation of CO2 on Nickel catalysts. The swap between methanation and the Reverse Water Gas-Shift reaction (CO2+H2 <=> CO+H2O) is driven by dynamics induced by some of the reaction intermediates. In particular, at low temperatures, CO accumulates on the Ni surface promoting the formation of Ni adatoms, which enhances further CO conversion to methane. At elevated temperatures, the adatom population decreases, and the selectivity towards CO increases. In the present example, the lack of understanding of the materials under operando conditions leads to poor representativeness of the structural models in the calculations. This introduces an error that accumulates with the energy evaluation error of Density Functional Theory simulations. Our work paves the way for including dynamic aspects of the materials under reaction conditions in microkinetic simulations.