Understanding the role of Co segregation on the carbon deposition over Ni–Co bimetal catalyst in dry reforming of methane

Abstract

Ni–Co bimetal catalysts showed the resistance to carbon deposition in DRM, and Co segregation on Ni surface plays very important role, but the underlying mechanism remains unclear. Hence, in current research, Ni and Ni–Co bimetal catalysts were prepared, and fixed-bed tests, characterizations and DFT calculations were carried out to uncover the effect of doped Co on the carbon formation and elimination process. DFT calculations suggested that Co segregation could promote the transfer of charge from the surface to CO2 and further affect CO2 activation. To some extent, the higher the Co concentrations on Ni surface, the more charge in adsorbed CO2, and the stronger ability for CO2 activation, which could produce more O and OH species to participate in CH consumption and C elimination. Furthermore, Co segregation could promote CH oxidation and C hydrogenation, which could inhibit the formation of carbon deposition and promote the C elimination. In addition, DFT calculations results were verified by experiments and characterizations, and found that Co segregation could reduce the amount of carbon deposition and lower the graphitization degree of carbon deposition, thus the resistance to carbon deposition in Ni–Co bimetal catalysts is improved.