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. 2018 Jan 9;8(1):33.
doi: 10.3390/nano8010033.

Surface Decoration of ZnWO₄ Nanorods with Cu₂O Nanoparticles to Build Heterostructure with Enhanced Photocatalysis

Lingyu Tian  1 , Yulan Rui  2 , Kelei Sun  3 , Wenquan Cui  4 , Weijia An  5
Affiliations

Surface Decoration of ZnWO₄ Nanorods with Cu₂O Nanoparticles to Build Heterostructure with Enhanced Photocatalysis

Lingyu Tian et al. Nanomaterials (Basel). .

Abstract

The surface of ZnWO₄ nanorods was decorated with Cu₂O nanoparticles (Cu₂O/ZnWO₄) prepared through a precipitation method. The Cu₂O nanoparticles were tightly deposited on the ZnWO₄ surface and had average diameters of 20 nm. The nanoparticles not only promoted the absorption and utilization of visible light but also facilitated the separation of photogenerated charge carriers. This brought an improvement of the photocatalytic activity. The 5 wt % Cu₂O/ZnWO₄ photocatalyst displayed the highest degrade efficiency for methylene blue (MB) degradation under visible light, which was 7.8 and 2 times higher than pure ZnWO₄ and Cu₂O, respectively. Meanwhile, the Cu₂O/ZnWO₄ composite photocatalyst was able to go through phenol degradation under visible light. The results of photoluminescence (PL), photocurrent, and electrochemical impedance spectra (EIS) measurements were consistent and prove the rapid separation of charge, which originated from the match level structure and the close contact with the interface. The radical and hole trapping experiments were carried out to detect the main active substances in the photodegradation process. The holes and ·O₂- radicals were predicted to dominate the photocatalytic process. Based on the characterization analysis and experiment results, a possible photocatalytic mechanism for enhancing photocatalytic activity was proposed.

Keywords: ZnWO4; degradation; nanoparticles; photocatalysis.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
X-Ray Diffraction (XRD) patterns of ZnWO4 and Cu2O/ZnWO4 photocatalysts.
Figure 2
Figure 2
Transmission Electron Microscopy (TEM) images of (a) ZnWO4; (b) Cu2O/ZnWO4.
Figure 3
Figure 3
(a) UV-visible light (UV-vis) diffuses reflection spectra of pure ZnWO4, Cu2O and Cu2O/ZnWO4 samples; (b) the band gap energies of ZnWO4 and Cu2O.
Figure 4
Figure 4
X-Ray Photoelectron Spectroscopy (XPS) spectra of Cu2O/ZnWO4 sample: (a) Survey of the sample; (b) Zn 2p; (c) Cu 2p and (d) W 4f.
Figure 5
Figure 5
Photoluminescence (PL) spectra of ZnWO4 and Cu2O/ZnWO4 composites.
Figure 6
Figure 6
Photocurrent-time curves of bulk ZnWO4 and Cu2O/ZnWO4 composites under visible light (>420 nm) irradiation with 30 s light on/off cycles.
Figure 7
Figure 7
Electrochemical Impedance Spectra (EIS) plots of pure ZnWO4 and as-prepared various Cu2O/ZnWO4 samples irradiated with visible light.
Figure 8
Figure 8
(a) UV-Vis spectral changes of methylene blue (MB) aqueous solution in the presence of 5 wt % Cu2O/ZnWO4 photocatalyst; (b) the activity of different catalysts to degrade MB in visible light.
Figure 9
Figure 9
Stability investigation of MB photocatalytic degradation over Cu2O/ZnWO4.
Figure 10
Figure 10
Linear relationship between ln(C0/C) and light time of phenol degradation.
Figure 11
Figure 11
First-order rate constant values of photogenerated active species trapped in the system of photocatalytic degradation of MB by Cu2O/ZnWO4 under visible light.
Figure 12
Figure 12
Schematic illustration of photo-generated carriers’ transportation for Cu2O/ZnWO4 composite.
See this image and copyright information in PMC

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