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

Ammonia is an indispensable chemical. Photocatalytic NH 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 flow efficiently produces NH. The surface OVs behave as the N 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 and Cl. These consecutive photoreactions produce NH 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 with 0.05% solar-to-chemical conversion efficiency, thus exhibiting significant potential of the seawater system for artificial photosynthesis.