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 mu mol g- 1h- 1, and the C2H4 yield can reach a high value of 40.46 mu mol g- 1h- 1 and the selectivity of 56.98 %. This work provides new insights into the coupling of C-C to generate C2 hydrocarbons.