N-graphyne surrounded Bi2S3/BiOBr composites: In-situ ultrasound-assisted synthesis and superior photocatalytic activity

Abstract

In this work, a collection of N-graphyne surrounded Bi2S3/BiOBr composites are firstly synthesized by sonochemical method. The as-prepared ternary composites are composed of nanosheets with average thickness around 25 nm. And, the best absorbability of N-graphyne-Bi2S3/BiOBr composites to rhodamine B is confirmed to be 445.0 mg/g, which is 1.36 folds larger than that of Bi2S3/BiOBr (327.5 mg/g). Moreover, the optimal N-graphyne-Bi2S3/BiOBr composites achieve a 1.17-, 1.68-, and 1.19-folds enhancements towards the visible-light driven photocatalytic degradation of rhodamine B, tetracycline, and methylene blue compared to Bi2S3/BiOBr, respectively. And, it is established that the primary active species in photocatalytic degradation process is superoxide radical (O2–). In addition, under UV–Vis light, the highest NH3 generation rate of N-graphyne-Bi2S3/BiOBr composites in water (i.e., 1.400 μmol⋅gcat−1⋅h−1) is 3.7 times higher than that of Bi2S3/BiOBr. Additionally, the stability of N-graphyne-Bi2S3/BiOBr composites is confirmed by 89 % retention of Rhodamine B degradation efficiency and no obvious change of XRD patterns in the fifth cycle compared to that of the first cycle. Furthermore, the tests of photo-current, the photoluminescence spectra, Tafel plots, Mott-Schottky curves, electrochemical impedance, etc. are methodically adopted to explore the photocatalytic mechanism. To put it succinctly, this work puts forwards a new path for the develop of effective BiOBr-based ternary photocatalysts.