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

• The Bi 2 S 3 /OV-Bi 2 MoO 6 S-scheme heterojunction is constructed using a simple in-situ anion exchange process enabling oxygen vacancy (OV) abundant Bi 2 MoO 6 microspheres with surface deposited Bi 2 S 3 . • The as-fabricated Bi 2 S 3 /OV-Bi 2 MoO 6 functioned as an effective photocatalyst to convert N 2 -to-NH 3 under mild conditions without any sacrificial agent. • The photocatalytic NH 3 production rate reached 126 μmol g cat −1 under visible light for 2.5 h with 2% Bi 2 S 3 /OV-Bi 2 MoO 6 photocatalyst, which was 8 fold higher than Bi 2 MoO 6 . • The S-scheme heterojunction accelerated the e − / h + pairs spatial separation and accumulation on the Bi 2 S 3 and Bi 2 MoO 6 side, respectively, thus simultaneously strengthening both OER and NRR half-reactions. Photocatalytic ammonia generation via nitrogen reduction reaction (NRR) is a green and prospective nitrogen fixation technique. However, NRR is often hampered by the high N 2 adsorption/activation energies and is accompanied by a slow kinetics oxygen evolution reaction (OER). Herein, a robust Bi 2 S 3 /OV-Bi 2 MoO 6 S-scheme heterojunction is constructed using a simple in-situ anion exchange process, which enables oxygen vacancy (OVs) abundant Bi 2 MoO 6 microspheres with surface deposited Bi 2 S 3 . The as-fabricated Bi 2 S 3 /OV-Bi 2 MoO 6 functioned as an effective photocatalyst to convert N 2 -to-NH 3 under mild conditions. The photocatalytic NH 3 /NH 4 + production rate reached 126 μmol g cat −1 under visible light for 2.5 h with 2% of Bi 2 S 3 /OV-Bi 2 MoO 6 photocatalyst, which was 8-fold higher than pristine Bi 2 MoO 6 . Furthermore, the as-fabricated Bi 2 S 3 /Bi 2 MoO 6 heterojunction exhibited good selectivity, high stability and reproducibility. The excellent photocatalytic NRR performance was ascribed to the Bi 2 S 3 /Bi 2 MoO 6 heterojunction formed subsequent to the strong interaction between Bi 2 S 3 and Bi 2 MoO 6 . The OVs facilitated the chemical adsorption process allowing activation of N 2 molecule on the Bi 2 S 3 /Bi 2 MoO 6 . Simultaneously, the S-scheme heterojunction prolonged the lifetime of photogenerated carriers, accelerated the electrons/holes spatial separation and accumulation on the Bi 2 S 3 (reduction) and Bi 2 MoO 6 side (oxidation), respectively, thus strengthening both OER and NRR half-reactions. This simple in-situ anion exchange method offers a novel technique for strengthening OER and NRR half-reactions in Bi-based photocatalysts for effective photocatalytic ammonia generation.