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Photoexcited Properties of Tin Sulfide Nanosheet-Decorated ZnO Nanorod Heterostructures

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ABSTRACT

In this study, ZnO–Sn2S3 core–shell nanorod heterostructures were synthesized by sputtering Sn2S3 shell layers onto ZnO rods. The Sn2S3 shell layers consisted of sheet-like crystallites. A structural analysis revealed that the ZnO–Sn2S3 core–shell nanorod heterostructures were highly crystalline. In comparison with ZnO nanorods, the ZnO–Sn2S3 nanorods exhibited a broadened optical absorption edge that extended to the visible light region. The ZnO–Sn2S3 nanorods exhibited substantial visible photodegradation efficiency of methylene blue organic dyes and high photoelectrochemical performance under light illumination. The unique three-dimensional sheet-like Sn2S3 crystallites resulted in the high light-harvesting efficiency of the nanorod heterostructures. Moreover, the efficient spatial separation of photoexcited carriers, attributable to the band alignment between ZnO and Sn2S3, accounted for the superior photocatalytic and photoelectrochemical properties of the ZnO–Sn2S3 core–shell nanorod heterostructures.

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a Current density vs. potential curves for various nanorod samples with and without light illumination. b Cyclic current density vs. time curves for various nanorod samples under chopped light illumination
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Fig6: a Current density vs. potential curves for various nanorod samples with and without light illumination. b Cyclic current density vs. time curves for various nanorod samples under chopped light illumination

Mentions: Figure 6a shows the photocurrent density vs. the potential curves of the ZnO and ZnO–Sn2S3 nanorods with and without light illumination. Under light irradiation, the measured photocurrent densities of the ZnO and ZnO–Sn2S3 nanorods were approximately 0.32 and 0.84 mA cm−2 at 0.5 V, respectively. The ZnO nanorod sample yielded relatively low photocurrent under light illumination. However, the sequential combination of the Sn2S3 shell layers onto the surfaces of the ZnO nanorods significantly enhanced the photocurrent density. These results confirmed that the ZnO–Sn2S3 nanorods exhibited efficient visible light absorption ability and excellent interfacial charge transformation. Figure 6b displays the photocurrent responses of the ZnO and ZnO–Sn2S3 nanorods at an applied potential of 0.5 V. The ZnO–Sn2S3 nanorods exhibited steady and highly repeatable photocurrent responses during on–off cycles of light illumination. Notably, photoexcited electrons in the Sn2S3 are injected into ZnO because of the band alignment of the heterostructure, as discussed earlier in the present text. This is attributed to the type II band alignment between the ZnO and Sn2S3; the effective photoexcited charge separation has been widely reported in other heterostructure systems [33, 34]. The aligned ZnO nanorods provide a conduction path, and numerous photoexcited electrons are transferred from Sn2S3 and ZnO to the F-doped SnO2 electrode and are then finally transferred to the platinum electrode. After the photogenerated carriers are transferred rapidly in the PEC system, the electrons travel through F-doped SnO2 to the platinum electrode and react with the electrolyte, yielding a reduction reaction, whereas the holes in the valence band of Sn2S3 react with the electrolyte, yielding an oxidation reaction [34]. Consequently, the ZnO nanorods coated with the Sn2S3 shell layers exhibit excellent PEC activity compared with that of pure ZnO rods. In this study, the superior PEC performance of the ZnO–Sn2S3 nanorod heterostructures is attributable to the increased contact area between the nanorods and adsorbed electrolyte molecules resulting from the unique three-dimensional sheet-like Sn2S3 layers of the ZnO–Sn2S3 rod heterostructures. Furthermore, Sn2S3 exhibits superior optical absorption ability, providing high visible light-harvesting efficiency. These factors account for the superior PEC activity of the ZnO–Sn2S3 nanorods in this study.Fig. 6


Photoexcited Properties of Tin Sulfide Nanosheet-Decorated ZnO Nanorod Heterostructures
a Current density vs. potential curves for various nanorod samples with and without light illumination. b Cyclic current density vs. time curves for various nanorod samples under chopped light illumination
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Fig6: a Current density vs. potential curves for various nanorod samples with and without light illumination. b Cyclic current density vs. time curves for various nanorod samples under chopped light illumination
Mentions: Figure 6a shows the photocurrent density vs. the potential curves of the ZnO and ZnO–Sn2S3 nanorods with and without light illumination. Under light irradiation, the measured photocurrent densities of the ZnO and ZnO–Sn2S3 nanorods were approximately 0.32 and 0.84 mA cm−2 at 0.5 V, respectively. The ZnO nanorod sample yielded relatively low photocurrent under light illumination. However, the sequential combination of the Sn2S3 shell layers onto the surfaces of the ZnO nanorods significantly enhanced the photocurrent density. These results confirmed that the ZnO–Sn2S3 nanorods exhibited efficient visible light absorption ability and excellent interfacial charge transformation. Figure 6b displays the photocurrent responses of the ZnO and ZnO–Sn2S3 nanorods at an applied potential of 0.5 V. The ZnO–Sn2S3 nanorods exhibited steady and highly repeatable photocurrent responses during on–off cycles of light illumination. Notably, photoexcited electrons in the Sn2S3 are injected into ZnO because of the band alignment of the heterostructure, as discussed earlier in the present text. This is attributed to the type II band alignment between the ZnO and Sn2S3; the effective photoexcited charge separation has been widely reported in other heterostructure systems [33, 34]. The aligned ZnO nanorods provide a conduction path, and numerous photoexcited electrons are transferred from Sn2S3 and ZnO to the F-doped SnO2 electrode and are then finally transferred to the platinum electrode. After the photogenerated carriers are transferred rapidly in the PEC system, the electrons travel through F-doped SnO2 to the platinum electrode and react with the electrolyte, yielding a reduction reaction, whereas the holes in the valence band of Sn2S3 react with the electrolyte, yielding an oxidation reaction [34]. Consequently, the ZnO nanorods coated with the Sn2S3 shell layers exhibit excellent PEC activity compared with that of pure ZnO rods. In this study, the superior PEC performance of the ZnO–Sn2S3 nanorod heterostructures is attributable to the increased contact area between the nanorods and adsorbed electrolyte molecules resulting from the unique three-dimensional sheet-like Sn2S3 layers of the ZnO–Sn2S3 rod heterostructures. Furthermore, Sn2S3 exhibits superior optical absorption ability, providing high visible light-harvesting efficiency. These factors account for the superior PEC activity of the ZnO–Sn2S3 nanorods in this study.Fig. 6

View Article: PubMed Central - PubMed

ABSTRACT

In this study, ZnO–Sn2S3 core–shell nanorod heterostructures were synthesized by sputtering Sn2S3 shell layers onto ZnO rods. The Sn2S3 shell layers consisted of sheet-like crystallites. A structural analysis revealed that the ZnO–Sn2S3 core–shell nanorod heterostructures were highly crystalline. In comparison with ZnO nanorods, the ZnO–Sn2S3 nanorods exhibited a broadened optical absorption edge that extended to the visible light region. The ZnO–Sn2S3 nanorods exhibited substantial visible photodegradation efficiency of methylene blue organic dyes and high photoelectrochemical performance under light illumination. The unique three-dimensional sheet-like Sn2S3 crystallites resulted in the high light-harvesting efficiency of the nanorod heterostructures. Moreover, the efficient spatial separation of photoexcited carriers, attributable to the band alignment between ZnO and Sn2S3, accounted for the superior photocatalytic and photoelectrochemical properties of the ZnO–Sn2S3 core–shell nanorod heterostructures.

No MeSH data available.