Shiraishi Yasuhiro, Hashimoto Masaki, Chishiro Kiyomichi, Moriyama Kenta, Tanaka Shunsuke, Hirai Takayuki
Research Center for Solar Energy Chemistry, and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan.
Department of Chemical, Energy, and Environmental Engineering, Kansai University, Suita 564-8680, Japan.
J Am Chem Soc. 2020 Apr 22;142(16):7574-7583. doi: 10.1021/jacs.0c01683. Epub 2020 Apr 8.
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.
氨是一种不可或缺的化学品。在环境条件下通过阳光照射利用水进行光催化固氮生产氨是一种很有前景的策略，尽管此前报道的催化剂活性不足。在此，我们表明，在氮气流下，对含有表面氧空位的半导体氯氧化铋（BiOCl-OVs）在含氯离子（Cl）的水中进行紫外光照射能高效产生氨。表面氧空位通过光生导带电子作为氮还原位点。价带空穴被催化剂层间氯的自氧化消耗。形成的次氯酸（HClO）吸收紫外光并光解为氧和氯。这些连续的光反应以水作为电子供体产生氨。溶液中的氯离子补偿了被去除的层间氯并抑制催化剂失活。在海水中对该催化剂进行模拟阳光照射能以0.05%的太阳能到化学能转换效率稳定地产生氨，从而显示出海水体系在人工光合作用方面的巨大潜力。
