One-step hydrothermal synthesis of ternary heterostructure stannic sulfide - bismuth sulfide - bismuth oxychloride (SnS2-Bi2S3-BiOCl) composite loaded on carbon felt for highly efficient piezocatalytic degradation of organic dyes and antibiotics

Abstract

The piezoelectric catalysis technique harnesses naturally occurring vibrational energy to remove organic pollutants from water in an environmentally friendly manner. In this study, a ternary heterostructure SnS₂-Bi₂S₃-BiOCl (S-B-B) composite was successfully synthesized via a one-step hydrothermal method and simultaneously deposited on the surface of carbon felt. The S-B-B heterojunction exhibits significantly enhanced piezoelectric catalytic activity compared to SnS₂, Bi₂S₃, and BiOCl, achieving a k value of 2.26 × 10⁻² min⁻¹ and a degradation efficiency of 89.9 % towards methyl orange (MO) dye after 100 min of ultrasonic degradation. This performance is markedly superior to the individual components, with k values of 3.80 × 10⁻⁴ min⁻¹ for SnS₂, 1.16 × 10⁻² min⁻¹ for BiOCl, and 1.31 × 10⁻² min⁻¹ for Bi₂S₃. Moreover, in addition to levofloxacin (LV), it demonstrates high removal efficiency for Congo red (CR), methylene blue (MB), tetracycline hydrochloride (TC-HCl), and sulfanilamide (SN). Furthermore, it can be loaded onto carbon felt for use in piezoelectric catalytic degradation of dyeing wastewater, highlighting its potential for practical applications. Trapping experiments suggest that singlet oxygen non-radicals and hydroxyl radicals play a critical role in the piezocatalytic degradation of organic contaminants. Based on LC-MS results, a possible degradation pathway for MO dye is proposed. Furthermore, DFT calculations confirm electron transfer from Bi₂S₃ to SnS₂ and BiOCl at the interfaces between SnS₂/Bi₂S₃ and BiOCl/Bi₂S₃. The piezoelectric mechanism of the S-B-B composite is also elucidated, highlighting the interaction and electron dynamics within the heterostructure.