A comparative DFT study of atomic and molecular oxygen adsorption on neutral and negatively charged Pd xCu 3−x ( x = 0–3) nano-clusters

Abstract

Adsorption of molecular and atomic oxygen on neutral and negatively charged Pd x Cu 3− x ( x = 0–3) nano-clusters have been studied by density functional theory. It has been observed that modes and energies of adsorption strongly depend on the charge and composition of the nano-clusters. The most stable adsorption mode for molecular oxygen on neutral Pd/Cu nano-clusters is to bridge Pd–Cu site (adsorption energy = −103.7 kJ mol −1) while on negatively charged nano-clusters bridging of Pd–Pd or Cu–Cu are more stable adsorption modes (adsorption energies = −140.9 and −172.9 kJ mol −1). Also, the most stable adsorption mode for atomic oxygen on neutral Pd/Cu nano-clusters is on the hollow site (adsorption energy = −111.9 kJ mol −1) while on negatively charged nano-clusters adsorption on top of Pd or Cu are the most stable adsorption modes (adsorption energies = −289.7 and −370.2 kJ mol −1). With increasing copper content the adsorption energy of molecular and atomic oxygen on neutral nano-clusters decrease while on negatively charged nano-clusters increase. Also, it has been shown that (I) increasing of copper content in nano-cluster and (II) adding of negative charge to nano-clusters weaken O–O bond which can increase the activity of the nano-cluster for dissociation of molecular oxygen. Moreover, it has been shown that dissociation of molecular oxygen on nano-clusters is exothermic and occurs more favorably on Pd/Cu nano-clusters compared to on Pd nano-cluster.