Effect of the Ni size on CH 4 /CO 2 reforming over Ni/MgO catalyst: A DFT study

Abstract

Abstract Carbon deposition is sensitive to the metal particle sizes of supported Ni catalysts in CH 4 /CO 2 reforming. To explore the reason of this phenomenon, Ni4, Ni8, and Ni12 which reflect the different cluster thicknesses supported on the MgO(100) slabs, have been employed to simulate Ni/MgO catalysts, and the reaction pathways of CH 4 /CO 2 reforming on Ni x /MgO(100) models are investigated by density functional theory. The reforming mechanisms of CH 4 /CO 2 on different Ni x /MgO(100) indicate the energy barriers of CH 4 dissociated adsorption, CH dissociation, and C oxidation three factors are all declining with the decrease of the Ni cluster sizes. The Hirshfeld charges analyses of three steps as described above show only Ni atoms in bottom two layers can obtain electrons from the MgO supporters, and the main electron transfer occurs between adsorbed species and their directly contacted Ni atoms. Due to more electron-rich Ni atoms in contact with the MgO supporters, the Ni/MgO catalysts with small Ni particles have a strong metal particle size effect and lead to its better catalytic activity.