Bi₄O₅Br₂ Nanoflower and CdWO₄ Nanorod Heterojunctions for Photocatalytic Synthesis of Ammonia

In this study, a Bi 4 O 5 Br 2 /CdWO 4 (BOB/CWO) composite photocatalyst was designed and prepared using a convenient hydrothermal method. A detailed investigation was carried out on the morphology, specific surface area, structure, optical properties, and photoelectric chemical properties of the BOB/CWO composite. The CdWO 4 nanorods were found to disperse on the surface of Bi 4 O 5 Br 2 nanoflowers, and their tight contact between CdWO 4 and Bi 4 O 5 Br 2 resulted in the formation of a heterojunction structure. By analysis of the band structure of the two semiconductors, it was found that the heterojunction worked in a type II mechanism, effectively improving the separation efficiency of electron–hole pairs. Therefore, the BOB/CWO composite exhibited high performance in photocatalytic N 2 fixation (PNF) reactions. The optimal BOB/CWO catalyst presents a PNF rate of 501 μmol L –1 g –1 h –1 under simulated sunlight irradiation, which was 5.7 and 3.1 times that of pure CdWO 4 and Bi 4 O 5 Br 2, respectively. Under visible-light illumination, the BOB/CWO heterojunction worked in a sensitized mechanism, and the coupling effect of CdWO 4 and Bi 4 O 5 Br 2 in boosting the PNF reaction could still be observed. The findings of this study are anticipated to offer practical knowledge about the design and synthesis of efficient photocatalysts for PNF.