Lignin derived carbon quantum dots and oxygen vacancies coregulated S-scheme LCQDs/Bi2WO6 heterojunction for photocatalytic H2O2 production

Abstract

This study presents an innovative photocatalytic system utilizing waste biomass resources for sustainable synthesis of hydrogen peroxide (H₂O₂) and high-value lignin derivatives. A lignin derived carbon quantum dots (LCQDs) loaded S-scheme heterojunction photocatalyst LCQDs/Bi₂WO₆ (LCD/BWO) was synthesized via hydrothermal method. The LCD/BWO composite demonstrates exceptional H₂O₂ production rate (3.776 mmol h⁻¹ g⁻¹) and maintains 89.72 % activity retention after 5 cycles under visible light irradiation, representing a 5.97-fold enhancement over catalyst BWO-A. The performance leap stems from synergistic effects between LCQDs and oxygen vacancies (OVs) defects: the unique up-conversion luminescence of LCQDs combined with S-scheme charge transfer mechanism enhances light absorption and carrier separation efficiency, while interfacial OVs act as electron traps to prolong carrier lifetime. In situ electron paramagnetic resonance (In situ EPR) analysis revealed substantial generation of •O₂⁻ and •OH radicals on catalyst surfaces. Band structure characterization confirms optimized H₂O₂ synthesis through consecutive single-electron reactions. Synergistic regulation of band positions significantly enhances oxygen reduction reaction (ORR) and water oxidation reaction (WOR) capabilities. As lignin primarily originates from agricultural/forestry waste, this work not only provides new design strategies for efficient photocatalytic systems but also advances high-value utilization of waste biomass resources.