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Frontiers of Environmental Science & Engineering

Front. Environ. Sci. Eng.    2020, Vol. 14 Issue (4) : 72
Utilizing transparent and conductive SnO2 as electron mediator to enhance the photocatalytic performance of Z-scheme Si-SnO2-TiOx
Jing Gu1, Hongtao Yu1, Xie Quan1(), Shuo Chen1, Junfeng Niu2
1. Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
2. Research Center for Eco-Environmental Engineering, Dongguan University of Technology, Dongguan 523808, China
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• A novel Z-scheme Si-SnO2-TiOx with SnO2 as electron mediator is first constructed.

• Transparent and conductive SnO2 can pass light through and promote charge transport.

• VO from SnO2 and TiOx improve photoelectrochemical performances.

• Efficient photocatalytic degradations originate from the Z scheme construction.

Z-scheme photocatalysts, with strong redox ability, have a great potential for pollutants degradation. However, it is challenging to construct efficient Z-scheme photocatalysts because of their poor interfacial charge separation. Herein, by employing transparent and conductive SnO2 as electron mediator to pass light through and promote interfacial charge transportation, a novel Z-scheme photocatalyst Si-SnO2-TiOx (1<x<2) was constructed. The Z-scheme photocatalyst displayed an order of magnitude higher photocurrent density and a 4-fold increase in open-circuit potential compared to those of Si. Moreover, the onset potential shifted negatively for approximately 2.2 V. Benefiting from these advantages, this Z-scheme Si-SnO2-TiOx exhibited efficient photocatalytic performance toward phenol degradation and mineralization. 75% of the phenol was degraded without bias potential and 70% of the TOC was removed during phenol degradation. Other typical pollutants such as bisphenol A and atrazine could also be degraded without bias potential. Introducing a transparent and conductive electron mediator to construct Z-scheme photocatalyst gives a new sight to the improvement of photocatalytic performance in Z scheme.

Keywords Z-scheme photocatalyst      Tin oxide      Electron mediator      Organic pollutant     
Corresponding Author(s): Xie Quan   
Just Accepted Date: 07 April 2020   Issue Date: 08 May 2020
 Cite this article:   
Jing Gu,Hongtao Yu,Xie Quan, et al. Utilizing transparent and conductive SnO2 as electron mediator to enhance the photocatalytic performance of Z-scheme Si-SnO2-TiOx[J]. Front. Environ. Sci. Eng., 2020, 14(4): 72.
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Jing Gu
Hongtao Yu
Xie Quan
Shuo Chen
Junfeng Niu
Fig.1  SEM images of Si-SnO2 ((a) surface and (b) profile) and Si-SnO2-TiOx ((c) profile), (d) EDS spectrum and element mapping of (e) Si, (f) Sn, (g) Ti and (h) O.
Fig.2  (a) XRD patterns of Si-SnO2-TiOx, Si-SnO2 and Si (Insert is the full figure), (b) I-V relation of Si-SnO2 measured by four-point probe, (c) DRS and (d) ESR curves of the samples.
Fig.3  XPS spectra of Sn 3d ((a) surface, (b) etched for 30 s, (c) etched for 240 s) and O 1p ((d) surface, (e) etched for 30 s, (f) etched for 240 s) valence states of Si-SnO2 and XPS spectra of Ti 2p ((g) surface, (h) etched for 30 s, (i) etched for 240 s) and O 1p ((j) surface, (k) etched for 30 s, (l) etched for 240 s) valence states of Si-SnO2-TiOx.
Fig.4  Chopped photocurrent responses of (a) Si under UV/vis light, (b) Si, Si-TiOx and Si-SnO2-TiOx under UV/vis light, (c) Si-SnO2-TiOx under UV/vis and visible light and (d) CV tests of the as-prepared samples and (e) Photocurrent responses and (f) PL emission of the samples
Fig.5  (a) Phenol degradation at different potentials and (b) phenol degradation at zero potential with or without scavengers, (c–d) kinetic curves of the degradation process, (e) schematic diagram of degradation mechanism and (f) TOC removal at zero potential.
Fig.6  Schematic diagram of band position analysis of the components
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