Quantum-Chemical Study of C-H Bond Activation in Methane on Ni-Cu Oxide and Sulfide Clusters

Density functional theory ( DFT) (PBE) was used to simulate the breaking of C-H bond in methane on copper-enriched Ni-Cu clusters as the first step of dry reforming of methane. The models of catalysts were the nanoscale clusters NiCu11S6(PH3)(8), NiCu11S6, NiCu11O6(PH3)(8), and NiCu11O6. The binding energy of methane with the clusters was calculated, and the activation energy of the step CH4* -> + H* was determined. It was found from the obtained data that the NiCu11O6 catalytic system is the most promising for CH4 activation in terms of both kinetics (activation energy is 99 kJ/mol) and thermodynamics (energy change of the step is -29 kJ/mol). The coking resistance of the NiCu11O6 cluster was estimated by simulating the CH adsorption followed by dissociation (CH* -> C* + H*). The calculated activation energy of this step is rather high: 159 kJ/mol.