Facile synthesis of highly efficient ZnO/ZnFe^sub 2^O^sub 4^ photocatalyst using earth-abundant sphalerite and its visible light photocatalytic activity

• Published in: Applied catalysis. B, Environmental Vol. 226; p. 324
• 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: Amsterdam Elsevier BV 15.06.2018
• Subjects: Absorption spectroscopy; Antisite defects; Catalysts; Catalytic activity; Chemical synthesis; Deactivation; Differential thermal analysis; Differential thermogravimetric analysis; Dyes; E coli; Electron microscopy; Feasibility studies; Heat treatment; Inactivation; Iron; Minerals; Optimization; Oxidation; Phase ratio; Photocatalysis; Photocatalysts; Photodegradation; Raman spectra; Raman spectroscopy; Scanning electron microscopy; Sphalerite; Substrates; Thermal analysis; Thermogravimetry; X-ray absorption spectroscopy; X-ray diffraction; Zinc; Zinc ferrites; Zinc oxide; Zincblende
• ISSN: 0926-3373; 1873-3883

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.