Facile synthesis of highly efficient ZnO/ZnFe2O4 photocatalyst using earth-abundant sphalerite and its visible light photocatalytic activity

• Published in: Applied catalysis. B, Environmental Vol. 226; pp. 324 - 336
• Main Authors: Li, Yan, Li, Yanzhang, Yin, Yidong, Xia, Dehua, Ding, Hongrui, Ding, Cong, Wu, Jing, Yan, Yunhua, Liu, Yi, Chen, Ning, Wong, Po Keung, Lu, Anhuai
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.06.2018
• Subjects: Earth-abundant; Natural sphalerite; Photocatalytic activity; Visible light; ZnO/ZnFe2O4; Natural sphalerite; Photocatalytic activity; ZnO/ZnFe2O4; Visible light; Earth-abundant
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2017.12.051

[Display omitted] •Visible-light photocatalyst ZnO/ZnFe2O4 is fabricated firstly by calcining natural Fe-bearing sphalerite.•ZnO/ZnFe2O4 exhibits improved photocatalytic performance for azo dye degradation and bacterial disfection.•The formation of matched band alignment between ZnO and ZnFe2O4 improves the separation efficiency of carriers.•The optimization of ZnFe2O4 spinel structure significantly enhances photocatalytic activities.•This method is a creative guidance via utilizing natural minerals to fabricate coupled photocatalysts. Micrometer-scale ZnO/ZnFe2O4 coupled photocatalyst is synthesized via a simple, one-step thermal treatment performing on natural Fe-bearing sphalerite ((Zn, Fe)S). In situ high-temperature X-ray diffraction (XRD), thermogravimetry, differential thermal analysis (TG/DTA) and scanning electron microscopy (SEM) results indicated that octahedral ZnFe2O4 (∼5 μm) formed on the surface of substrate-like ZnO (tens of microns) derived from the oxidation of sulfides upon heating to 800 °C in air for 1 h, and the two components kept stable phase ratio at 3:7 (wt%) from 900 °C (sample M-900) to 1200 °C (sample M-1200). X-ray absorption spectroscopy (XAS) and Raman spectra revealed that more Zn atoms in ZnFe2O4 of M-1200 occupied tetrahedral sites than M-900, resulting in a sharper A1g mode (∼647 cm−1), more ordered spinel structure and less antisite defects. Compared with visible-light responsive sphalerite (Zn, Fe)S, M-1200 performed more 200 nm of red-shifted optical absorption, 2.5 times at most higher the incident photon-to-electron conversion efficiency (IPCE) and 2–3-fold photocatalytic efficiency towards degradation of methyl orange and inactivation of Escherichia coli K-12. Besides, the photocatalytic activities of M-1200 preponderate over M-900, typical visible-light catalyst ZnFe2O4 and ZnO/ZnFe2O4 mechanically mixed sample. The optimization of lattice structure and the establishment of special band alignment were suggested to be remarkably beneficial to the separation of photogenerated electrons-holes and promote the photocatalytic performance. This study would enlighten a feasible and efficient strategy to fabricate coupled photocatalyst by utilizing Earth-abundant and low-cost natural minerals for solving environmental problems.