Photocatalytic Dinitrogen Fixation with Water on Bismuth Oxychloride in Chloride Solutions for Solar-to-Chemical Energy Conversion

Ammonia is an indispensable chemical. Photocatalytic NH 3 production via dinitrogen fixation using water by sunlight illumination under ambient conditions is a promising strategy, although previously reported catalysts show insufficient activity. Herein, we showed that ultraviolet light irradiation of a semiconductor, bismuth oxychloride with surface oxygen vacancies (BiOCl-OVs), in water containing chloride anions (Cl – ) under N 2 flow efficiently produces NH 3 . The surface OVs behave as the N 2 reduction sites by the photoformed conduction band electrons. The valence band holes are consumed by self-oxidation of interlayer Cl – on the catalyst. The hypochloric acid (HClO) formed absorbs ultraviolet light and undergoes photodecomposition into O 2 and Cl – . These consecutive photoreactions produce NH 3 with water as the electron donor. The Cl – in solution compensates for the removed interlayer Cl – and inhibits catalyst deactivation. Simulated sunlight illumination of the catalyst in seawater stably generates NH 3 with 0.05% solar-to-chemical conversion efficiency, thus exhibiting significant potential of the seawater system for artificial photosynthesis.