Mechanisms of Hydrogen-Assisted CO2 Reduction on Nickel.

Mechanistic details of catalytic reactions are critical to the development of improved catalysts. Here, we perform high quality Born-Oppenheimer molecular dynamics simulations of the reaction mechanisms associated with hydrogen-assisted CO2 reduction on Ni(110). The simulation results show direct theoretical evidence for both associative and redox mechanisms in the reaction of atomic hydrogen with CO2. Because H2 is dissociatively chemisorbed on Ni(110) with nearly unit probability, the mechanisms we find are also relevant to the reverse water-gas shift reaction (H2 with adsorbed CO2). Furthermore, we provide the first real-time demonstration of both Eley-Rideal (ER) and hot atom (HA) mechanisms when H impinges on adsorbed CO2, and we show that both occur even for low kinetic energies. The trade-off between ER or HA mechanisms is found to be strongly dependent on CO2 coverage. The results are compared with recent gas/surface measurements.