Dual Charge Transfer Mechanisms in Intimately Bonded S‐scheme Heterojunction Photocatalyst with Expeditious Activity toward Environmental Remediation

Abstract Fabrication of a photocatalyst with the desired characteristics of high charge isolation and expeditious photocatalytic performance is crucial in photocatalysis. Constructing an interfacial chemically bonded S‐scheme heterojunction is an effective path to the realization of high interfacial charge transfer and performance. Herein, Mg‐Bi₂O₃/dark gray g‐C₃N₄ (MBOdCN) S‐scheme heterojunction with Bi‐N bond bridges is successfully constructed using an in situ calcination strategy for oxytetracycline (OTC) degradation. The MBOdCN (1:5) displays outstanding performance with efficiency and rate constant of 99.56% and 0.0235 min⁻¹, respectively. The synergy of n‐π* transition, Mg defects, and Bi–N bond bridges in the MBOdCN enhances the performance of the S‐scheme heterojunction. X‐ray photoelectron spectroscopy (XPS) analysis, work function measurements, and density functional theory (DFT) reveal the formation of MBOdCN S‐scheme heterojunction. In this system, trapping experiments and electron‐spin resonance (ESR) spectroscopy confirm the predominance of ^•O₂⁻ > h⁺ > ^•OH during OTC degradation. The degradation pathways and byproducts are investigated with LC‐MS and the toxicity study is undertaken on the OTC degradation byproducts and photocatalytic materials. This work provides a holistic understanding of the novel S‐scheme heterojunction by introducing interfacial chemical bond bridges and defects as dual charge transfer channels.