Efficient photocatalytic degradation of 2,4,6-trichlorophenol by Z-scheme α-MnO2/Bi2S3 enriched with double vacancies under visible light: Mechanism and degradation pathway

Abstract

The widespread use and release of 2,4,6-Trichlorophenol (TCP) poses a significant risk to water bodies and ecosystems. Designing efficient and stable catalysts for photocatalytic degradation of TCP remains a great challenge. In this paper, a Z-scheme α-MnO₂/Bi₂S₃ (Mn/Bi) composite enriched with oxygen (O_Vs) and sulfur (S_Vs) vacancies is designed for photocatalytic degradation of TCP. 60-Mn/Bi achieved 88 % degradation efficiency for 20 mg/L TCP solution. The reaction rate (k) of 60-Mn/Bi is 6.46 and 4.41 times higher than that of α-MnO₂ and Bi₂S₃, respectively. The catalyst exhibited high catalytic activity in a wide pH range and high resistance to anion. In addition, the cycling performance of 60-Mn/Bi is relatively stable, and the ion leaching rate is low. The Z-scheme mechanism is confirmed by characterization and DFT, which effectively retained the strong redox capacity. The abundant vacancy structure enhances the adsorption of TCP and promotes the migration of photogenerated carriers. In addition, the rod-shaped Bi₂S₃ provides a carrier for α-MnO₂ nanoparticles, which effectively alleviates agglomeration and thus exposes more active sites. Three possible degradation pathways were explored by LC-MS and DFT. This study provides a facile method and guidance for the preparation of Z-scheme catalysts to improve photocatalytic degradation performance.