Predicting Adhesion Energies of Late Transition Metal Nanoparticles to Oxide Support Surfaces Using Oxide Reducibility and Metal Oxophilicity: Toward Predicting Catalyst Performance
Nida Janulaitis, Charles T. Campbell
Abstract
Adhesion energies between metal nanoparticles and catalyst supports are important for understanding the reactivity and stability of supported nanoparticle catalysts, since they determine the metal chemical potential versus particle size, and this chemical potential dictates both surface reactivity and the rate of deactivation by sintering. A general correlation is presented here for predicting adhesion energies of late transition metals to clean oxide surfaces based on the metal element’s oxophilicity and atomic volume and the oxide surface’s reducibility (as estimated by its oxygen vacancy formation energy). Previous work had shown that the adhesion energies of metals to MgO(100) and to CeO 2 (111) correlate proportionally with the oxophilicity per unit area of the metal, and we show here that this also holds for rutile-TiO 2 (100). A linear relationship is then discovered between the proportionality constants measured for these three oxide surfaces and their surface oxygen vacancy formation energies. Adhesion energies of metals to these and several other oxide surfaces are scaled using this correlation between the proportionality constant and the oxygen vacancy formation energy of the oxide, giving a single trend line for the predicting adhesion energies of many late transition metals to many oxide surfaces with a standard deviation of 0.47 J/m 2 over their 4 J/m 2 range. We also show that the surface oxygen vacancy formation energy can be estimated based on the heat of reduction of the bulk oxide to its next lower oxidation state, at least for the very stable oxide facets studied here.