Effect of Cu doping on Ni surface on CO formation pathways during the methane dry reforming reaction

Three different Cu-Ni/ZrO2 surfaces are constructed in this paper to investigate the variation rules of carbon migration paths when CH4 and CO2 act as the carbon source. Actually, Cu doping can affect the migration pathway of carbon atom from CH4 and CO2 to CO. When CH4 is the carbon source, the carbon migration process is mainly accomplished through the oxygen-assisted pathway, and Cu doping shows no effect on the dominance of the oxygen-assisted pathway. However, the carbon migration process mainly follows the hydrogen-assisted pathway when CO2 is the carbon source. Meanwhile, the activation energy gap between the hydrogen-assisted pathway and the direct dissociation pathway is reduced by Cu doping. The reduction of activation energy gap proves that the mode of carbon migration of CO2 from the dominance of a single pathway to the competition of a dual pathway. Furthermore, the active energy of oxidation of CH species is always lower compared with deep cracking. The difference of the activation energy of two reaction process of CH species raises up as Cu doping ratio increases. The expansion of difference of activation energy proves that Cu doping can induce CH species to prefer to be oxidized rather than direct cracking, lowering the generation of deposited carbon atoms. In addition, Cu doping promotes the oxidation process of surface carbon atoms and improves the anti-carbon deposition ability of the catalyst surface. Moreover, the order of adsorption strength of CO on different Cu-Ni/ZrO2 is: Ni/ZrO2> Cu1Ni2/ZrO2> Cu2Ni1/ZrO2. And the charge transfer from the catalyst surface to CO molecules is also reduced by Cu doping. Therefore, the interaction between CO and the catalyst surface can be weakened by Cu doping, which is conducive to the desorption of CO molecule.