In Situ-Synthesized Bi2S3/BiOI with S-Scheme Heterojunction as a High-Efficiency Photocatalyst for Formaldehyde and Methyl Orange Degradation

An effective approach to eliminating organic pollutants is to develop step-scheme (S-scheme) heterojunction photocatalysts, because such heterojunctions can effectively promote photogenerated carrier separation while maximally retaining strong redox capability. Herein, S-scheme Bi 2 S 3 /BiOI (BBS) photocatalysts were synthesized using the in situ ion exchange method. Morphology and structure of BBS, as well as its photoelectrochemical properties, among others, were studied and analyzed. The photocatalytic activity of BBS was evaluated by degrading formaldehyde (HCHO) and methyl orange (MO). Compared with BiOI and Bi 2 S 3 , BBS catalysts demonstrated a remarkable improvement in photocatalytic performance under irradiation with visible light ( λ  > 400 nm). With the highest photocatalytic efficiency, BBS-0.01 achieved degradation rates of 80% for HCHO (0.16 mg L −1 ) in 90 min and 97% for MO in 210 min. This notable enhancement in photocatalytic performance is attributed to the in situ ion exchange method, which constructs heterojunctions with intimate interfacial contact, uniform component distribution, high carrier separation efficiency, abundant active sites, and excellent stability. Furthermore, the S-scheme heterostructure further enhances catalytic performance owing to its well-matched energy band structures, efficient carrier separation, and the combined effect with the internal electric field (IEF). In addition, BBS photocatalysts exhibit a stronger visible-light response capability, consequently enhancing the overall photocatalytic efficiency. Hence, the BBS heterojunction photocatalyst presented in this work is a highly promising material for environmental applications under visible light. Graphical