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Superior adsorption and photoinduced carries transfer behaviors of dandelion-shaped Bi 2 S 3 @MoS 2 : experiments and theory

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ABSTRACT

The enhanced light-harvesting capacity and effective separation of photogenerated carriers in fantastic hierarchical heterostructures enjoy striking attention for potential applications in the field of solar cells and photocatalysis. A three-dimensional (3D) dandelion-shaped hierarchical Bi2S3 microsphere compactly decorated with wing-shaped few layered MoS2 lamella (D-BM) was fabricated via a facile hydrothermal self-assembly process. Especially, polyethylene glycol (PEG) has been proven as the vital template to form D-BM microsphere. Importantly, the as-prepared D-BM microsphere presents pH-dependent superior adsorption behavior and remarkable visible light photocatalytic activity for degradation of organic dyestuffs (Rhodamine B/RhB and Methylene blue/MB), far exceeding those for the pure Bi2S3 and MoS2. It is understandable that D-BM with high surface area possesses more active sites and promotes light utilization due to the unique porous structure with outspread wings. Besides, based on the experiments and theoretical calculations, the staggered type II band alignment of D-BM permits the charge injection from Bi2S3 to MoS2, subsequently accelerates the separation and restrains the recombination of carriers, leading to excellent photocatalytic activity, as well as the photoconductance and photoresponse performance (with Ilight/Idark ratio 567).

No MeSH data available.


(a) TEM image of D-BM microstructures. (b) The surface of D-BM and the inset is the SAED pattern. (c,d) HRTEM images of D-BM. (e) SEM image of D-BM and the corresponding EDS mapping images of Bi, S, and Mo elements. (f) The corresponding EDS line scan along the pink line in (e).
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f3: (a) TEM image of D-BM microstructures. (b) The surface of D-BM and the inset is the SAED pattern. (c,d) HRTEM images of D-BM. (e) SEM image of D-BM and the corresponding EDS mapping images of Bi, S, and Mo elements. (f) The corresponding EDS line scan along the pink line in (e).

Mentions: In addition, a sequence of TEM and HRTEM images of D-BM nanocomposite have been employed to reveal more specific structural information. In Fig. 3a, homogeneous MoS2 sheets are detected at the edge of each Bi2S3 nanorod from the low magnification TEM survey. Not only Fig. 3b,c clarify the intimate interfacial contact between MoS2 sheets and elongated Bi2S3 rods, but also they indicate that the MoS2 sheets are ultrathin compared with the pure MoS2 flowers. In the HRTEM image (Fig. 3e), the lattice fringes of d = 3.54 Å and d = 3.74 Å, corresponding to the (130) and (101) planes of Bi2S3, respectively28. The coated MoS2 exhibits the lattice spacing of 6.19 Å, which matches well with the (002) planes of hexagonal MoS231. Furthermore, the related cleaved crystal structure in theoretical section indicates the distance between adjacent Bi atoms on the (130) crystal surface of Bi2S3 (3.4148 nm), which is eleven intervals of the adjacent S atoms on the (001) crystal surface of MoS2 (0.3169 nm × 11)45. It is believed that Bi2S3 nanorods might be available for the growth of the MoS2 nanosheets to form the heterostructure between the mutual effect of S and Bi atoms. Thus, it can be inferred that the MoS2 sheets, with about 5–8 layers, embellished at the surface of the Bi2S3 rods. Moreover, the selected area electron diffraction (SAED) pattern (inset of Fig. 3b) further proves the mixed-phase nature of single crystal Bi2S3 (bright diffraction spots) and layered superimposed MoS2 sheets (diffraction rings). In order to accurately confirm the elemental composition and spatial distribution, energy dispersive X-ray spectrometry (EDS) analysis in Fig. 3e have been performed. The well-proportioned distributions of S, Bi, and Mo can be obtained from the mapping results. Besides, the EDS line scan (Fig. 3f) of the marked region sheds light on the unique hierarchical heterostructure, as well as in agreement with SEM and TEM observation.


Superior adsorption and photoinduced carries transfer behaviors of dandelion-shaped Bi 2 S 3 @MoS 2 : experiments and theory
(a) TEM image of D-BM microstructures. (b) The surface of D-BM and the inset is the SAED pattern. (c,d) HRTEM images of D-BM. (e) SEM image of D-BM and the corresponding EDS mapping images of Bi, S, and Mo elements. (f) The corresponding EDS line scan along the pink line in (e).
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5304175&req=5

f3: (a) TEM image of D-BM microstructures. (b) The surface of D-BM and the inset is the SAED pattern. (c,d) HRTEM images of D-BM. (e) SEM image of D-BM and the corresponding EDS mapping images of Bi, S, and Mo elements. (f) The corresponding EDS line scan along the pink line in (e).
Mentions: In addition, a sequence of TEM and HRTEM images of D-BM nanocomposite have been employed to reveal more specific structural information. In Fig. 3a, homogeneous MoS2 sheets are detected at the edge of each Bi2S3 nanorod from the low magnification TEM survey. Not only Fig. 3b,c clarify the intimate interfacial contact between MoS2 sheets and elongated Bi2S3 rods, but also they indicate that the MoS2 sheets are ultrathin compared with the pure MoS2 flowers. In the HRTEM image (Fig. 3e), the lattice fringes of d = 3.54 Å and d = 3.74 Å, corresponding to the (130) and (101) planes of Bi2S3, respectively28. The coated MoS2 exhibits the lattice spacing of 6.19 Å, which matches well with the (002) planes of hexagonal MoS231. Furthermore, the related cleaved crystal structure in theoretical section indicates the distance between adjacent Bi atoms on the (130) crystal surface of Bi2S3 (3.4148 nm), which is eleven intervals of the adjacent S atoms on the (001) crystal surface of MoS2 (0.3169 nm × 11)45. It is believed that Bi2S3 nanorods might be available for the growth of the MoS2 nanosheets to form the heterostructure between the mutual effect of S and Bi atoms. Thus, it can be inferred that the MoS2 sheets, with about 5–8 layers, embellished at the surface of the Bi2S3 rods. Moreover, the selected area electron diffraction (SAED) pattern (inset of Fig. 3b) further proves the mixed-phase nature of single crystal Bi2S3 (bright diffraction spots) and layered superimposed MoS2 sheets (diffraction rings). In order to accurately confirm the elemental composition and spatial distribution, energy dispersive X-ray spectrometry (EDS) analysis in Fig. 3e have been performed. The well-proportioned distributions of S, Bi, and Mo can be obtained from the mapping results. Besides, the EDS line scan (Fig. 3f) of the marked region sheds light on the unique hierarchical heterostructure, as well as in agreement with SEM and TEM observation.

View Article: PubMed Central - PubMed

ABSTRACT

The enhanced light-harvesting capacity and effective separation of photogenerated carriers in fantastic hierarchical heterostructures enjoy striking attention for potential applications in the field of solar cells and photocatalysis. A three-dimensional (3D) dandelion-shaped hierarchical Bi2S3 microsphere compactly decorated with wing-shaped few layered MoS2 lamella (D-BM) was fabricated via a facile hydrothermal self-assembly process. Especially, polyethylene glycol (PEG) has been proven as the vital template to form D-BM microsphere. Importantly, the as-prepared D-BM microsphere presents pH-dependent superior adsorption behavior and remarkable visible light photocatalytic activity for degradation of organic dyestuffs (Rhodamine B/RhB and Methylene blue/MB), far exceeding those for the pure Bi2S3 and MoS2. It is understandable that D-BM with high surface area possesses more active sites and promotes light utilization due to the unique porous structure with outspread wings. Besides, based on the experiments and theoretical calculations, the staggered type II band alignment of D-BM permits the charge injection from Bi2S3 to MoS2, subsequently accelerates the separation and restrains the recombination of carriers, leading to excellent photocatalytic activity, as well as the photoconductance and photoresponse performance (with Ilight/Idark ratio 567).

No MeSH data available.