Role of magnetization on catalytic pathways of non-oxidative methane activation on neutral iron carbide clusters

Methane has emerged as a promising fuel due to its abundance and clean combustion properties. It is also a raw material for various value-added chemicals. However, the conversion of methane to other chemicals such as olefins, aromatics, and hydrocarbons is a difficult task. In recent years, ionic iron carbide clusters have been explored as potential catalysts for efficient direct methane conversion. Herein, we have investigated the gas-phase methane conversion process on various neutral iron carbide clusters with different Fe:C ratios using density functional theory. Reaction pathways were studied on mononuclear and trinuclear iron carbide clusters in the three lowest energy spin multiplicity channels. Three descriptors - methane binding energy, the effective energy barrier for C-H bond activation, and the effective energy required for methyl radical evolution - were chosen to identify the best catalyst among the clusters considered. Isomers of Fe3C6 (Fe3C6-iso) and Fe3C9 (Fe3C9-iso) are recognized as being the most promising catalysts among all the clusters considered here because they require the least methyl radical evolution energy, a step that is crucial in methane conversion to higher hydrocarbon but also requires the most energy.