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

• DOI: 10.1021/jacs.0c01683
• Publication Date: 2020-04-08T16:57:22Z
• Authors: Yasuhiro Shiraishi; Masaki Hashimoto; Kiyomichi Chishiro; Kenta Moriyama; Shunsuke Tanaka; Takayuki Hirai
• Keywords: 02 engineering and technology; 0210 nano-technology; 01 natural sciences; 7. Clean energy; 0104 chemical sciences

Ammonia is an indispensable chemical. Photocatalytic NH3 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 N2 flow efficiently produces NH3. The surface OVs behave as the N2 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 O2 and Cl-. These consecutive photoreactions produce NH3 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 NH3 with 0.05% solar-to-chemical conversion efficiency, thus exhibiting significant potential of the seawater system for artificial photosynthesis.