The use of hydrogen in ammonia synthesis, and in oxygen and carbon dioxide catalytic reduction - the reaction mechanisms

We report three paradigmatic examples of atomic-level computational modeling of catalytic processes of hydrogen use in the energy and environmental fields: ammonia synthesis (in particular the Haber-Bosch, HB, process), oxygen reduction reaction (ORR), and the carbon dioxide reduction reaction (CO2RR). Reaction mechanisms for these processes are illustrated first in a general overview and then in the specific cases of: a single-crystal Fe bcc(111) surface for HB, nanostructured systems (nanoporous particles, a small cluster, and nanowire) for ORR, and subnanometer (or ultranano) Ni3 and Ni2Cu clusters for CO2RR, respectively. Our goal is to show the potentialities of predictive computational modeling in this field as a basis for progress and possible breakthroughs in the rational design of catalysts satisfying the stringent societal requirements to H2 utilization for sustainable energy and matter cycles.