Fabrication of Ti-doped Bi2S3/NiO p-n heterojunction with enhanced visible-light–driven photocatalytic activity

Abstract

The present work is focused on the hydrothermal synthesis of Bi2S3, Tix-doped Bi2S3 (x = 0.3, 0.6, and 1 %), NiOy/Bi2S3 (y = 1, 3, and 5 %), and 0.6 %Ti-doped Bi2S3/1%NiO, which showed a high photocatalytic activity in the range of visible light. It can be attributed to the high BET surface area and p-n junction formed between n-type Bi2S3 and p-type NiO, resulting in the efficient separation/transition of photogenerated electron-hole pairs and a decreased recombination rate. Furthermore, Ti (IV) doping increased the band gap of Bi2S3, improving the transfer rate of photo-induced electrons and extending the lifetime of charge carriers. It is noteworthy that the amount of both the Ti and NiO components plays a crucial role in increasing photocatalytic activity. Among the synthesized samples, the 0.6 % Ti-doped Bi2S3/1%NiO nanocomposite represented the optimum photocatalytic efficiency by eliminating 80 % of methylene blue (MB, 20 mgL-1) after 500 min visible light illumination. In 180 min, only 63 % of the total organic carbon (TOC) from the MB solutions was removed under optimal circumstances. In general, the photocatalytic process of Ti-doped Bi2S3/ NiO p-n heterojunction was proved by the formation of •OH and •O2– radicals during the degradation reaction, confirmed by scavenger tests and Mott-Schottky studies. Moreover, gas chromatography-mass spectrometry (GC–MS) was employed to investigate the degradation products and determine the smaller resulting fragmented compounds. Furthermore, the design of new p-n heterojunctions as the photocatalyst for removing the azo dyes will aid the treatment of environmental contaminants, especially water purification.