Visible-light degradation of sulfonamides by Z-scheme ZnO/g-C3N4 heterojunctions with amorphous Fe2O3 as electron mediator

Guanglan Di; Zhiliang Zhu; Hua Zhang; Jianyao Zhu; Yanling Qiu; Daqiang Yin; Stephan Küppers

doi:10.1016/j.jcis.2018.11.100

Visible-light degradation of sulfonamides by Z-scheme ZnO/g-C₃N₄ heterojunctions with amorphous Fe₂O₃ as electron mediator

J Colloid Interface Sci. 2019 Mar 7:538:256-266. doi: 10.1016/j.jcis.2018.11.100. Epub 2018 Nov 27.

Authors

Guanglan Di¹, Zhiliang Zhu², Hua Zhang¹, Jianyao Zhu³, Yanling Qiu⁴, Daqiang Yin⁴, Stephan Küppers⁵

Affiliations

¹ State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China.
² State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China. Electronic address: zzl@tongji.edu.cn.
³ State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, China.
⁴ Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University, Shanghai 200092, China.
⁵ Research Center Jülich, ZEA-3, Jülich 52425, Germany.

PMID: 30513467
DOI: 10.1016/j.jcis.2018.11.100

Abstract

ZnO grafted amorphous Fe₂O₃ matrix (ZnO/Fe₂O₃) was coupled with g-C₃N₄ to synthesize heterojunction photocatalysts with a loosened multilayered structure. The ZnO/Fe₂O₃/g-C₃N₄ exhibited enhanced photocatalytic performance in the degradation of sulfamethazine under visible-light irradiation (λ > 420 nm), with an optimum photocatalytic degradation rate approximately 3.0, 2.4 times that of pure g-C₃N₄ and binary ZnO/g-C₃N₄. Moreover, the target sulfonamides spiked in actual surface water samples could be efficiently photodegraded by ZnO/Fe₂O₃/g-C₃N₄ after 8 h of irradiation, demonstrating its practical potential. An amorphous Fe₂O₃-mediated Z-scheme mechanism was proposed for the charge transfer at the heterojunction surface, which involved a Fe(III)/Fe(II) oxidation-reduction center that favored the retarded charge recombination and improved photocatalytic activity. Such a mechanism was well supported by the direct detection of surface generated O₂^- and OH reactive species. Finally, detailed transformation pathways were proposed based on the photodegradation products identified by QToF-MS analyses. This work provides an illustrative strategy for developing efficient Z-scheme photocatalysts for water purification, by taking advantage of amorphous Fe-based oxides in the semiconductor lattice matching.

Keywords: Degradation pathways; Electron mediator; Sulfonamides degradation; Z-scheme mechanism; ZnO/Fe(2)O(3)/g-C(3)N(4).