Valence engineering at the interface of MoS2/Mo2C heterostructure for bionic nitrogen reduction

The natural nitrogenase is still the most efficient catalyst on earth to reduce the ambient N2 into ammonia. The central part of the molecular machine is powered by a metallic core, usually a molybdenum atom, whose coordination valence state remains an enigma for us to unveil and mimic. Unlike the flexible bio-enzyme, inorganic heterogeneous catalysts are usually rigid in the coordination structure, making their valence states invariable, except some localized defects. In this study, we successfully synthesized a two-dimensional MoS2/Mo2C electrocatalyst, which contains a heterostructured interface with efficient charge and magnetism separation, exhibiting a gradual and broad valence state transition from Mo4+ to Mo2+. Density functional theory (DFT) calculations reveal that Mo3+ sites at the interface have a strong N2 adsorption energy of − 0.75 eV with the side-on configuration, and an activated hydrogenation of *NH2 species. This bionic electrocatalyst displays a splendid performance in nitrogen reduction reaction with a Faradic efficiency of 42 % at −0.1 V vs RHE.