In-situ anion exchange based Bi2S3/OV-Bi2MoO6 heterostructure for efficient ammonia production: A synchronized approach to strengthen NRR and OER reactions

Photocatalytic ammonia generation via nitrogen reduction reaction (NRR) is a green and prospective ni-trogen fixation technique. However, NRR is often hampered by the high N-2 adsorption/activation ener-gies and is accompanied by a slow kinetics oxygen evolution reaction (OER). Herein, a robust Bi2S3/OV-Bi2MoO6 S-scheme heterojunction is constructed using a simple in-situ anion exchange process, which enables oxygen vacancy (OVs) abundant Bi2MoO6 microspheres with surface deposited Bi2S3. The as-fabricated Bi2S3/OV-Bi2MoO6 functioned as an effective photocatalyst to convert N-2-to-NH3 under mild conditions. The photocatalytic NH3/NH4+ production rate reached 126 mu mol g(cat)(-1) under visible light for 2.5 h with 2% of Bi2S3/OV-Bi2MoO6 photocatalyst, which was 8-fold higher than pristine Bi2MoO6. Fur-thermore, the as-fabricated Bi2S3/Bi2MoO6 heterojunction exhibited good selectivity, high stability and reproducibility. The excellent photocatalytic NRR performance was ascribed to the Bi2S3/Bi2MoO6 hetero-junction formed subsequent to the strong interaction between Bi2S3 and Bi2MoO6. The OVs facilitated the chemical adsorption process allowing activation of N-2 molecule on the Bi2S3/Bi2MoO6. Simultane-ously, the S-scheme heterojunction prolonged the lifetime of photogenerated carriers, accelerated the electrons/holes spatial separation and accumulation on the Bi2S3 (reduction) and Bi2MoO6 side (oxida-tion), respectively, thus strengthening both OER and NRR half-reactions. This simple in-situ anion ex-change method offers a novel technique for strengthening OER and NRR half-reactions in Bi-based pho-tocatalysts for effective photocatalytic ammonia generation. (C) 2021 Published by Elsevier Ltd on behalf of Chinese Society for Metals.