Unraveling the C–C coupling mechanism on Ni–O–Fe asymmetric sites for photocatalytic nonoxidative coupling of methane

Photocatalytic non-oxidative coupling of methane is an attractive strategy for CH4 to C2 conversion, how to facilitate the photogenerated charge separation and accelerate the C–C coupling to promote the reaction kinetics remains a great challenge. Herein, a symbiotic r-Fe2O3/NiO heterostructure with robust interfaces is constructed in situ. The coherent interface not only provides unique Ni–O–Fe asymmetric sites, but also achieves the separation and transport of photogenerated charge. The unbalanced charge density distribution of two adjacent methyl or methylene at the Ni–O–Fe asymmetric site alleviates the dipole repulsion of the C–C coupling, and promotes C–C coupling to form C2 hydrocarbons. Under visible light irradiation, the optimal r-Fe2O3/NiO performs a brilliant C2 activity up to 71.00 μmol g−1h−1, and the C2H4 yield can reach a high value of 40.46 μmol g−1h−1 and the selectivity of 56.98 %. This work provides new insights into the coupling of C–C to generate C2 hydrocarbons.