Internal electric field boosting visible photocatalytic degradation of antibiotics by flower-like CeO2/Bi2S3 S-scheme heterojunctions

Abstract

An internal electric field can be formed by constructing a heterojunction to achieve effective separation of photogenerated electrons and holes, which is able to solve the problem of easy compounding of photogenerated carriers in a single semiconductor photocatalyst. This research employs a hydrothermal synthesis technique to develop S-scheme heterojunction photocatalysts composed of cerium oxide and bismuth sulfide (CeO₂/Bi₂S₃) and evaluates their efficacy in degrading TC under visible light. The formation of S-scheme heterojunctions was confirmed by X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations showing that electrons migrate, and the internal electric field of the S-scheme heterojunctions achieves the separation of the electron–hole pairs, retaining the redox capacity of useful electrons and holes, which is responsible for the enhancement of the photocatalytic activity. The synthesized CeO₂/Bi₂S₃-2 photocatalysts demonstrated a TC degradation rate of 82.43% after a duration of 120 minutes under visible light irradiation. The rate constant of this performance was two times greater than that of CeO₂ alone and 2.75 times greater than that of Bi₂S₃. In addition, free radical trapping experiments and electron paramagnetic resonance results confirmed that ·O₂⁻ and h⁺ are active substances in the photocatalytic reaction process. Liquid chromatography-mass spectrometry (LC-MS) detected possible intermediates and suggested degradation pathways. This study has significant implications for the future development and enhancement of S-scheme heterojunction photocatalysts, contributing to advancements in photocatalytic materials.