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

Abstract

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 C-2(+) selectivity and O2- consumption for the formation of COx, respectively. The optimum catalytic activity, represented by the C-2(+) 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-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. (C) 2019 Elsevier Inc. All rights reserved.