Lattice Control of WO3 Nanoflowers by Heat Treatment and Construction of WO3/CdS/α-S Heterojuntion

doi:10.15541/jim20200023

Abstract

Abstract:

In order to study the influence mechanism of heat treatment and heterostructures on the photoelectrochemical effect of WO₃, monoclinic WO₃ nanoflowers were synthesized by low-temperature solvothermal method. The active crystal fact, grain size and crystallinity of WO₃ were controlled by heat treatment. Furthermore, WO₃/CdS/α-S heterojunction was obtained by modified chemical bath deposition, and the concentration effect of its photoelectrochemical performance was studied. The results show that the (200) crystal plane with photoelectrochemical activity is the main exposed crystal plane of WO₃, and the proportion of the exposed crystal plane increases with the heat treatment temperature increasing. The WO₃ nanoflower treated at 350 ℃ showed the highest photoresponse current. By constructing WO₃/CdS/α-S heterojunction, the material's absorption in the visible light region is enhanced, and the overall efficiency of photo-generated carrier separation is improved by sacrificing a small amount of carriers, which promotes the macroelectronic chemical effects of WO₃.

Key words: tungsten oxide, nanoflower, step-scheme heterostructure, photocurrent response

CLC Number:

O646

LIN hai, SU Weitao, ZHU Yu, PENG Pai, FENG Miao, YU Yan. Lattice Control of WO₃ Nanoflowers by Heat Treatment and Construction of WO₃/CdS/α-S Heterojuntion[J]. Journal of Inorganic Materials, 2020, 35(12): 1349-1356.

Figures/Tables 15

Fig. 1 SEM images of WO3 nanoflower precursor (a) and W-350 (b); XRD patterns of the samples heat-treated at different temperatures (c); (002), (020), and (200) crystal plane diffraction peak positions (d), diffraction peak integrated area ratios (e) and grain sizes (f) obtained by Rietveld refinement varied as functions of heat treatment temperature

Fig. S1 SEM images of precursor (a), W-310 (b), W-330 (c), W-370 (d), W-390 (e), W-410 (f), W-430 (g), and W-450 (h).

Fig. S2 Rietveld refinement results of XRD data from W-310 (a), W-330 (b), W-350 (c), W-370 (d), W-390 (e), W-410 (f), W-430 (g), W-450 (h)

Table 1 Rietveld refinement results of XRD data of the samples heat-treated at different temperatures

Sample	(002) 2θ/(°)	(020) 2θ/(°)	(200) 2θ/(°)	(002) Peak area ratio/%	(020) Peak area ratio/%	(200) Peak area ratio/%	R/%^a	E/%^b
W-310	23.302	23.805	23.989	31.60736	31.93592	36.45672	7.96	7.22
W-330	23.191	23.744	24.063	28.51362	31.21225	40.27413	8.45	9.08
W-350	23.152	23.724	24.110	25.48277	33.41551	41.10171	8.71	8.87
W-370	23.136	23.698	24.171	24.13370	35.22923	40.63707	7.77	8.89
W-390	23.128	23.685	24.217	20.52815	33.02325	46.4486	8.74	8.72
W-410	23.113	23.643	24.203	31.60641	29.83773	38.55586	9.62	11.08
W-430	23.126	23.668	24.268	30.26410	31.89507	37.84083	8.92	8.88
W-450	23.066	23.604	24.202	28.08145	34.16319	37.75536	8.84	9.0

Fig. 2 Raman spectra (a) and UV-Vis-IR absorption spectra (b) of the samples heat-treated at different temperatures

Fig. S3 Tauc plots of W-310 (a), W-330 (b), W-350 (c), W-370 (d), W-390 (e), W-410 (f), W-430 (g), W-450 (h) and the band gaps Eg obtained from the intersection of the absorption edge intercept line

Fig. S4 Raman spectra of WO3 precursor and representative heat-treated samples (a) and the WO3 sample heat-treated above 350 ℃ (b)

Fig. S5 FT-IR spectra of WO3 precursor and heat-treated samples

Fig. 3 Photocurrent response curves (a), photocurrent response peak values (b) and IPCE plots (c) of the samples heat-treated at different temperatures; Mott-Schottky curve of W-350 (d) Colourful version is available on offical website

Fig. 4 SEM image of W-350-30C (a); XRD patterns of W-350 and W-350-30C(b); TEM images of W-350-30C (c) and W-350-30C (d)

Fig. S6 EDX results of W-350-10C (a), W-350-20C (b), W-350-30C (c), and W-350-40C (d)

Fig. 5 XPS spectrum of sample W-350-30C (a); XPS high-resolution spectra of W4f (b), O1s (c), Cd3d (d) and S2p (e) for sample W- 350-30C; UV-Vis-IR absorption spectra (f) and photos (g) of γ-WO3 nanoflowers with different amounts of CdS/α-S modified on the surface Colourful version is available on offical website

Fig. 6 Photocurrent response curves(a), photocurrent response peak values(b), and IPCE plots(c) of γ-WO3 nanoflowers modified with different amounts of CdS/α-S on the surface; EIS plots of W-350 and W-350-30C(d) Colourful version is available on offical website

Fig. 7 Schematic diagram of charge carriers transfer in γ-WO3 nanoflowers with CdS/α-S modified on the surface

Fig. S7 UV-Vis spectra of methylene blue solution after absorbed by W-350 in the dark and UV irradiation for different time (a); Variation of methylene blue degradation rate with different time (b)

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Lattice Control of WO₃ Nanoflowers by Heat Treatment and Construction of WO₃/CdS/α-S Heterojuntion

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