ReaxFF Molecular Dynamic Simulations of ZnO Nanocluster and Films in H2 Atmosphere

Abstract

Reactive molecular dynamics simulations were performed to explore the structural evolution of a ZnO nanocluster and (0001) and (1010) surfaces under a H2 atmosphere at different temperatures. The mechanisms of H2 dissociation and water formation were analyzed. Our simulations reveal that there are two pathways for H2 dissociation and three routes for water formation on the surfaces. The nanocluster is more active for H2 dissociation and water formation than the two surfaces. The gas–solid interactions lead to outward displacement of the substrate O atoms. While the O-terminated surface of the (0001) facet is active for H2 dissociation and water formation, the Zn-terminated one is inactive for the dissociation. Unlike the (0001) surface which is more easily reduced, the (1010) surface is readily hydroxylated. Water formation and desorption results in surface oxygen depletion and Zn aggregation which lead to surface metallization, in accordance with the experimental observations. Our simulations show that...