Combined experimental and density functional theory (DFT) studies on the catalyst design for the oxidative coupling of methane

Catalytic descriptors were studied to design optimum catalysts for the oxidative coupling of methane (OCM) by combining density functional theory (DFT) calculations and actual reaction experiments. SrTiO₃ perovskite catalysts, selected for OCM, were modified using metal dopants, and their electronic structures were calculated using the DFT method. The CH₃ adsorption energy E_ads(CH₃) and the oxygen vacancy formation energy E_f(vac) exhibited volcano-type correlations with the C₂₊ selectivity and O₂-consumption for the formation of CO_x, respectively. The optimum catalytic activity, represented by the C₂₊ selectivity, was obtained for E_ads(CH₃) = −2.0 to −1.5 eV, indicating that overly strong adsorption of methyl radicals (or easily dissociated C[sbnd]H bonds of methane) and relatively insufficient oxygen supplementation to the catalyst surface improve deep oxidation to CO and CO₂. Praseodymium (Pr)- and neodymium (Nd)-doped SrTiO₃ catalysts confirm the DFT-predicted optimum electronic structure of the OCM catalysts.