Atomistic simulations of the adsorption and migration barriers of Cu adatoms on ZnO surfaces using COMB potentials

Abstract

Cu/ZnO heterogeneous systems are used to catalyze the CO2 hydrogenation to methanol, but questions remain about the nature of the active site and the role of Cu-ZnO interactions in the catalyst performance. The way in which ZnO surfaces support Cu clusters and stabilize their active sites is a key factor for maintaining catalyst activity. Processes such as sintering, alloying and encapsulation may play an important role in the activity of the catalyst but are difficult to model directly with density functional theory (DFT). In this work, we report the development of charge-optimized many-body (COMB) potentials to model the Cu/ZnO system. This potential is then used in conjugation with the dimer method, which uses the first derivative of the potential energy and the initial state of the transition to find saddle points, to examine the migration barriers of Cu adatoms on Cu and ZnO surfaces. These findings are validated against the results of density functional theory (DFT) calculations and published experimental data. (C) 2012 Elsevier B.V. All rights reserved.