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

Publication date: 15 June 2018
Source:Applied Catalysis B: Environmental, Volume 226
Author(s): Yan Li, Yanzhang Li, Yidong Yin, Dehua Xia, Hongrui Ding, Cong Ding, Jing Wu, Yunhua Yan, Yi Liu, Ning Chen, Po Keung Wong, Anhuai Lu
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.

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