Structure and Catalytic Activity of Gold Clusters Supported on Nitrogen-Doped Graphene

Abstract

Controlling the charge types of metal clusters on supports is of great importance in designing a noble-metal-free catalyst. Here, we designed two different types of N-doped graphene surfaces, the graphitic-like nitrogen-doped graphene G_nN and the pyridinic-like nitrogen-doped graphene G_nN,n′V. We found that in the Au₂₈/G_nN system, the Au atoms interact with C atoms. However, in the Au₂₈/G_nN,n′V system, the Au atoms interact with the N atoms. Specifically, the different bonding modes result in the charge state of the Au cluster being negative on the G_nN surface, whereas on the G_nN,n′V surface, the Au cluster is of positive charge. Therefore, it is possible to change the type of carbon–nitrogen bonding structure to control the charge types of gold clusters on nitrogen-doped graphene. In these two systems, the O₂ molecules prefer to be activated at the unsaturated and electron-rich bridge sites of the Au cluster. O₂ adsorption further enhances the charge transfer along the original directions at the Au₂₈ cluster/N-doped graphene substrate interfaces. However, the charge states of Au clusters slightly affect the activation of O–O bonds. The negatively charged Au cluster surface (Au₂₈/G_nN) exhibits better catalytic activity to CO oxidation under the trimolecular Eley–Rideal (3ER) mechanism and electrocatalytic reduction of CO₂ compared with the positively charged Au cluster surface (Au₂₈/G_nN,n′V). Our results are beneficial for accelerating the industrial application of nanometer-sized gold catalysts and provide a theoretical basis for the design and development of new catalysts.