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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 re flect 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 Nix/MgO(100) models are investigated by density functional theory.The reforming mechanisms of CH_4/CO_2 on different Nix/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.
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, Ni 4, Ni 8, and Ni 12 which re flect the different cluster thicknesses supported on the MgO (100) slabs, have has employed to simulate Ni / MgO catalysts, and the reaction pathways of CH 4 / CO 2 reforming on Nix / MgO (100) models the investigated by density functional theory. The reforming mechanisms of CH 4 / CO 2 on different Nix / MgO 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. Hirshfeld charges analyzes of three steps as described above show only Ni atoms in bottom two layers can obtain electrons from the 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 p articles have a strong metal particle size effect and lead to its better catalytic activity.