Abstract

The integration of biomass-derived carbon materials with advanced photocatalysts enables sustainable environmental remediation and clean energy production. Herein, a novel Ce₂Sn₂O₇– Sb₂O₃/biochar (CSOSB/BC) S-scheme heterojunction photocatalyst was synthesized via a combination of wet-impregnation and hydrothermal method for visible-light-driven metronidazole (MTZ) degradation and hydrogen evolution. XRD, FTIR, XPS, and Raman, confirmed the formation of a well-dispersed heterostructure with strong interfacial interactions, enhancing charge transfer and reactivity. Electrochemical impedance spectroscopy (EIS), transient photocurrent response, and Tauc plots, demonstrated the significant role of biochar in enhancing photocatalytic performance. These analyses confirmed that biochar improves charge separation, facilitates electron transfer, and boosts reactive oxygen species generation, ultimately leading to higher efficiency in MTZ degradation. Under optimized conditions, the CSOSB/BC composite achieved 95 % MTZ degradation and 700 μmol g⁻¹H₂ production under visible-light illumination. The effects of catalyst dosage, pollutant concentration, and pH were systematically evaluated. Also, LC-MS analysis revealed multiple ring-cleavage intermediates, with toxicity assessment confirming a significant reduction in environmental hazards. The composite exhibited excellent stability, maintaining 86 % activity after six cycles with preserved crystallinity and chemical integrity. These findings establish CSOSB/BC as a high-performance, durable, and scalable photocatalyst, offering a promising solution for pharmaceutical wastewater treatment and sustainable hydrogen production with minimal ecological risks.