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 CH(3) and H(2) at reaction temperatures above 1300 K, and acetylene production is dominant over ethylene production. The sensitivity analysis suggests that increasing the C(2) 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 C(2) product over the iron single-atom catalyst.