Effect of different doping ratios of Cu on the carbon formation and the elimination on Ni (111) surface: A DFT study

Abstract The focus of this paper is to solve the carbon deposition on Ni catalyst during dry reforming of methane (DRM). Cu has shown a great carbon resistance in DRM. Different doping ratio of Cu on Ni(111) surface, Cu1Ni8 and Cu6Ni3, have been studied through density functional theory (DFT), and the same procedure has been proceeded on Ni(111) to compare with. It is found that introducing Cu into Ni(111) surface can weaken the interaction between the surface and the absorbates, thus decrease the energy barrier of CH dissociation. Furthermore, two good linear relationships between the electron transferring from the surface to reactants and the energy barrier of CH dissociation and C2 formation have been discovered. In addition, the adsorption energy and activation energy are obtained, from which the dominated reaction pathway can be deduced. On the three surfaces, the dominated reaction pathways are the same, which can be shown as CH* + O* → HCO* → CO* + H*. However, on the surface of Cu6Ni3, the activation energy of CH oxidation is 0.63 eV, which is almost half the activation energy on the other two surfaces (1.24 eV and 1.24 eV), indicating that the Cu6Ni3 surface has the extraordinary ability of carbon resistance. Nevertheless, when C is formed on the three surfaces, it would accumulate rather than be oxidized, especially on the Cu6Ni3 surface because it has the lowest energy barrier (0.28 eV). In general, Cu6Ni3 surface having the best carbon resistance for CH* is more easily to be consumed through oxidation than through direct dissociation, thus it can be regarded as one of the potential candidates as the catalyst for DRM.