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

Abstract

Density functional theory (DFT) (PBE) was used for modeling of C–H bond breaking in methane on Ni–Cu clusters enriched in copper as the first stage of catalytic dry reforming of methane. Nanosized clusters NiCu11S6(PH3)8, NiCu11S6, NiCu11O6(PH3)8, NiCu11O6 are considered as catalyst models. The binding energy for methane with clusters was calculated and the activation energy of the \({\text{CH}}_{4}^{*}\) → \({\text{CH}}_{3}^{*}\) + H* step was determined. Based on the data obtained, it was found that the NiCu11O6 catalytic system is the most promising for CH4 activation both in kinetic (activation energy is 99 kJ/mol) and thermodynamic (step energy change is –29 kJ/mol) aspects. To assess the stability of the NiCu11O6 cluster towards coke formation, CH adsorption followed by dissociation (CH* → C* + H*) was modeled. The calculated value of the activation energy of this step is rather high, 159 kJ/mol.