Dual S-Scheme Charge Transfer Pathway in g-C <sub>3</sub> N <sub>4</sub> Quantum Dots/HKUST-1/TiO <sub>2</sub> Ternary Heterojunctions for Photocatalytic Pollutant Degradation
Yu Qiao, Hao Lü, Xusheng Wang, Xiangxin Xue, Juan Jian, Zhuo Wang, Peng Wang, Guangfu Liao
Abstract
Constructing dual S-scheme heterojunctions is an innovative strategy to boost photocatalysis by promoting photoinduced charge migration and retaining high redox potentials. Herein, we developed a facile green method to prepare g-C 3 N 4 quantum dots (QDs)/HKUST-1/TiO 2 dual S-scheme heterojunctions via depositing g-C 3 N 4 QDs in situ on spherical HKUST-1/TiO 2 . 15% g-C 3 N 4 QDs/HKUST-1/TiO 2 exhibited a significantly enhanced tetracycline (TC) degradation performance (97.02% degradation rate, 0.02177 min –1 reaction rate constant ( k app )) compared to g-C 3 N 4 QDs and HKUST-1/TiO 2, attributed to the enlarged specific surface area and accelerated charge separation (verified by experiments). It also showed excellent photostability. ESR confirmed • O 2 –, • OH, and h + as key active species. LC-MS and online FTIR spectroscopy analyzed TC degradation intermediates, pathways, and toxicity. Finally, experimental combined with theoretical calculation results further elucidated the possible dual S-scheme mechanism. The dual S-scheme mechanism endows this system with a relatively high redox capacity, fully utilizing the reducing ability of electrons on the conduction band of g-C 3 N 4 QDs and the oxidizing ability of holes on the valence band of TiO 2 . This work is contributory to designing novel dual S-scheme photocatalysts and efficient purification of wastewater in environmental remediation.