Mechanistic and microkinetic study of non-oxidative methane coupling on a single-atom iron catalyst

Non-oxidative methane coupling has promising economic potential, but the catalytic and radical reactions become complicated at high temperatures. Here, we investigate the mechanism of non-oxidative methane coupling on an iron single-atom catalyst using density functional theory, and evaluate the catalytic performance under various reaction conditions using microkinetic modelling and experiments. Under typical reaction conditions (1300 K and 1 bar), C-C coupling and subsequent dehydrogenation to produce ethylene shows comparable energetics between the gas-phase and catalytic pathways. However, the microkinetic analysis reveals that the iron single-atom catalyst converted methane to mainly CH₃ and H₂ at reaction temperatures above 1300 K, and acetylene production is dominant over ethylene production. The sensitivity analysis suggests that increasing the C₂ hydrocarbon yield by optimising the reaction conditions is limited. The experimental results obtained at 1293 K are consistent with the theoretical estimation that acetylene is the main C₂ product over the iron single-atom catalyst.