Theoretical Investigation of the Formation of Hydrogen Peroxide from H2 and O2 over Anionic Gold Clusters Aun- (n = 1−4)

Abstract

The direct synthesis of hydrogen peroxide (H2O2) from H2 and O2 over gold nanoparticles has been achieved in the past decade; however, our understanding for the mechanism is still far from complete. We present herein a density functional theory investigation of the formation mechanism of H2O2 from H2 and O2 on anionic gold clusters Aun- (n = 1−4). In all cases, the reaction proceeds via two elementary steps: initial H2 dissociation to form an OOH-containing intermediate and subsequent isomerization of this intermediate into a productlike intermediate. Energetically, the reactions over Au2- and Au4- are significantly less demanding than those over Au- and Au3-. In particular, Au- is relatively less active in the hydrogenation of O2 because the barrier of the rate-determining step is as high as 40.60 kcal mol-1. The barriers for both the odd- and even-numbered sequences slightly decrease with cluster size. The present results represent a prototype for the direct synthesis of H2O2 from H2 and O2 mediated by...