Electron transfer bridge inducing polarization of nitrogen molecules for enhanced photocatalytic nitrogen fixation†

Abstract

Ammonia (NH₃) plays a crucial role in the production of fertilizers, medicines, fibers, etc., which are closely relevant to the development of human society. However, the inert and nonpolar properties of NN seriously hinder artificial nitrogen fixation under mild conditions. Herein, we introduce a novel strategy to enhance the photocatalytic efficiency of N₂ fixation through the directional polarization of N₂ by rare earth metal atoms, which act as a local “electron transfer bridge.” This bridge facilitates the transfer of delocalized electrons to the distal N atom and redirects the polarization of adsorbed N₂ molecules. Taking cerium doped BiOCl (Ce–BiOCl) as an example, our results reveal that the electrons transfer to the distal N atom through the cerium atom, resulting in absorbed nitrogen molecular polarization. Consequently, the polarized nitrogen molecules exhibit an easier trend for NN cleavage and the subsequent hydrogenation process, and exhibit a greatly enhanced photocatalytic ammonia production rate of 46.7 μmol g⁻¹ h⁻¹ in cerium doped BiOCl, nearly 4 times higher than that of pure BiOCl. The original concept of directional polarization of N₂ presented in this work not only deepens our understanding of the N₂ molecular activation mechanism but also broadens our horizons for designing highly efficient catalysts for N₂ fixation.