Ostwald ripening of supported metal nanoparticles: Role of dimers and other general trends

Abstract

Supported ∼10 nm-sized metal particles are widely employed in applications. Under high temperatures typical for industrial catalysis, such nanoparticles often lose activity due to Ostwald ripening. This process is usually considered to occur via exchange of monomers between nanoparticles. The exchange of dimers is, however, also possible. We present equations allowing estimation of the relative role of these channels of ripening and the ratio of dimer and monomer concentrations on the support. The key factor here is the difference between the sublimation and dimer-formation energies. These energies were calculated for Pt, Pd, Ru, Rh, Ag, Au, and Cu by employing density functional theory with and without spin-orbital coupling. With this input, the conventional channel including monomers is found to dominate. The timescales of ripening and deviation of the power-law-growth exponents from the conventional ones are scrutinized as well.