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A dye-sensitized visible light photocatalyst-Bi24O31Cl10.

Wang L, Shang J, Hao W, Jiang S, Huang S, Wang T, Sun Z, Du Y, Dou S, Xie T, Wang D, Wang J - Sci Rep (2014)

Bottom Line: Density functional theory calculations reveal that the p-block elements determine the nature of the dispersive electronic structures and narrow band gap in Bi24O31Cl10.Bi24O31Cl10 exhibits excellent visible-light photocatalytic activity towards the degradation of Rhodamine B, which is promoted by dye sensitization due to compatible energy levels and high electronic mobility.In addition, Bi24O31Cl10 is also a suitable photoanode material for dye-sensitized solar cells and shows power conversion efficiency of 1.5%.

View Article: PubMed Central - PubMed

Affiliation: Center of Materials Physics and Chemistry and Department of Physics, Beihang University, Beijing 100191, P. R. China.

ABSTRACT
The p-block semiconductors are regarded as a new family of visible-light photocatalysts because of their dispersive and anisotropic band structures as well as high chemical stability. The bismuth oxide halides belong to this family and have band structures and dispersion relations that can be engineered by modulating the stoichiometry of the halogen elements. Herein, we have developed a new visible-light photocatalyst Bi24O31Cl10 by band engineering, which shows high dye-sensitized photocatalytic activity. Density functional theory calculations reveal that the p-block elements determine the nature of the dispersive electronic structures and narrow band gap in Bi24O31Cl10. Bi24O31Cl10 exhibits excellent visible-light photocatalytic activity towards the degradation of Rhodamine B, which is promoted by dye sensitization due to compatible energy levels and high electronic mobility. In addition, Bi24O31Cl10 is also a suitable photoanode material for dye-sensitized solar cells and shows power conversion efficiency of 1.5%.

No MeSH data available.


(a) Photo-degradation of RhB over the Bi24O31Cl10 sample under visible light (λ ≥ 420 nm) over 90 min. Inset is color evolution of RhB corresponding to the degradation time. (b) Photodecomposition of RhB on Bi24O31Cl10 under monochromatic light (λ = 550 nm) in over 9 hours. (c) Concentration changes of RhB with and without Bi24O31Cl10 under monochromatic light (λ = 550 nm). (d) Fluorescence emission spectra of RhB solution and Bi24O31Cl10/RhB suspension indicating a fluorescence quenching effect due to Bi24O31Cl10. (e) Transient photocurrent response of Bi24O31Cl10 and Bi24O31Cl10/RhB under visible light irradiation. The inset shows the photocurrent responses of Bi24O31Cl10 and Bi24O31Cl10/RhB under monochromatic light at 550 nm. (f) Nyquist impedance plots of Bi24O31Cl10 and Bi24O31Cl10/RhB in the dark and under visible light (λ ≥ 420 nm) conditions.
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f4: (a) Photo-degradation of RhB over the Bi24O31Cl10 sample under visible light (λ ≥ 420 nm) over 90 min. Inset is color evolution of RhB corresponding to the degradation time. (b) Photodecomposition of RhB on Bi24O31Cl10 under monochromatic light (λ = 550 nm) in over 9 hours. (c) Concentration changes of RhB with and without Bi24O31Cl10 under monochromatic light (λ = 550 nm). (d) Fluorescence emission spectra of RhB solution and Bi24O31Cl10/RhB suspension indicating a fluorescence quenching effect due to Bi24O31Cl10. (e) Transient photocurrent response of Bi24O31Cl10 and Bi24O31Cl10/RhB under visible light irradiation. The inset shows the photocurrent responses of Bi24O31Cl10 and Bi24O31Cl10/RhB under monochromatic light at 550 nm. (f) Nyquist impedance plots of Bi24O31Cl10 and Bi24O31Cl10/RhB in the dark and under visible light (λ ≥ 420 nm) conditions.

Mentions: From the de-coloration of RhB over Bi24O31Cl10 submicron platelets in visible light (Figure 4(a)), it was found that the absorptive intensity of RhB at a wavelength of 554 nm gradually decreases. The absorption band shifts to the shorter wavelength of 498 nm. This phenomenon reflects a typical process of photochemical N-de-ethylation of RhB to Rhodamine17. As the reaction time is increased above 75 min, the intensity of the absorption peak of Rhodamine (498 nm) continues to decrease, even though no peak shifting was observed. This indicates that the aromatic chromophore is still attacked by the active species leading to the decomposition of RhB45. This photocatalytic behaviour of Bi24O31Cl10 reflects intense photosensitization activity similar to that of another bismuth oxyhalide, BiOCl46. In order to confirm the photosensitization process in RhB/Bi24O31Cl10, a 300 W Xe lamp with a monochromatic light filter with the pass wavelength of 550 nm (see Supplementary Figure S7) was used for the irradiation light in a photocatalytic measurement, as shown in Figure 4(b) and 4(c). Note that RhB was still degraded, although Bi24O31Cl10 cannot absorb light with a wavelength of 550 nm. We rule out possible physical adsorption because the absorption peaks show an obvious shift during the photocatalytic process which indicates a chemical process. Figure 4(d) shows the fluorescence emission spectra of RhB with and without Bi24O31Cl10. The original RhB solution has a strong fluorescence emission at 580 nm (excited at 532 nm). When Bi24O31Cl10 colloidal suspension was added into the RhB solution, it can be seen that the fluorescence emission is remarkably decreased. The fluorescence quenching indicates that the excited electrons have not gone back to the internal energy level in RhB, instead they are transferred directly from the LUMO of RhB to the CB of Bi24O31Cl1047. This charge transfer was also confirmed by a photocurrent response measurement carried out on the Bi24O31Cl10 and Bi24O31Cl10/RhB samples by using visible light (λ ≥ 420 nm) and monochromatic light (550 nm) irradiation. Figure 4(e) shows a comparison of the photocurrent responses contributed by the Bi24O31Cl10 and Bi24O31Cl10/RhB samples. Bi24O31Cl10/RhB shows a much stronger photocurrent under visible light irradiation. The photocurrent of the Bi24O31Cl10/RhB gradually decreases in the cycling test because of photocatalytic degradation of RhB by Bi24O31Cl10. On the other hand, the Bi24O31Cl10/RhB sample produces obvious photocurrent under monochromatic light irradiation, while the Bi24O31Cl10 does not show any photoresponse. The photoresponse characterizations clearly demonstrate that Bi24O31Cl10 can be sensitized by dye molecules. Finally, the separation of photoinduced electron-hole pairs and charge transfer processes in Bi24O31Cl10/RhB were investigated by typical electrochemical impedance spectroscopy (EIS). The slope of EIS plots can be used to evaluate the efficiency of charge separation and transfer. A smaller slope reflects higher electron-hole separation and transfer efficiencies, and vice versa4849. The EIS Nyquist plot of a Bi24O31Cl10/RhB film on indium tin oxide (ITO) electrodes measured in the dark shows an even smaller slope in contrast to that of Bi24O31Cl10 measured under light irradiation, as displayed in Figure 4(f). This confirms that RhB indeed promotes the separation and transfer processes of photoinduced charge carriers in Bi24O31Cl10/RhB in visible light.


A dye-sensitized visible light photocatalyst-Bi24O31Cl10.

Wang L, Shang J, Hao W, Jiang S, Huang S, Wang T, Sun Z, Du Y, Dou S, Xie T, Wang D, Wang J - Sci Rep (2014)

(a) Photo-degradation of RhB over the Bi24O31Cl10 sample under visible light (λ ≥ 420 nm) over 90 min. Inset is color evolution of RhB corresponding to the degradation time. (b) Photodecomposition of RhB on Bi24O31Cl10 under monochromatic light (λ = 550 nm) in over 9 hours. (c) Concentration changes of RhB with and without Bi24O31Cl10 under monochromatic light (λ = 550 nm). (d) Fluorescence emission spectra of RhB solution and Bi24O31Cl10/RhB suspension indicating a fluorescence quenching effect due to Bi24O31Cl10. (e) Transient photocurrent response of Bi24O31Cl10 and Bi24O31Cl10/RhB under visible light irradiation. The inset shows the photocurrent responses of Bi24O31Cl10 and Bi24O31Cl10/RhB under monochromatic light at 550 nm. (f) Nyquist impedance plots of Bi24O31Cl10 and Bi24O31Cl10/RhB in the dark and under visible light (λ ≥ 420 nm) conditions.
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f4: (a) Photo-degradation of RhB over the Bi24O31Cl10 sample under visible light (λ ≥ 420 nm) over 90 min. Inset is color evolution of RhB corresponding to the degradation time. (b) Photodecomposition of RhB on Bi24O31Cl10 under monochromatic light (λ = 550 nm) in over 9 hours. (c) Concentration changes of RhB with and without Bi24O31Cl10 under monochromatic light (λ = 550 nm). (d) Fluorescence emission spectra of RhB solution and Bi24O31Cl10/RhB suspension indicating a fluorescence quenching effect due to Bi24O31Cl10. (e) Transient photocurrent response of Bi24O31Cl10 and Bi24O31Cl10/RhB under visible light irradiation. The inset shows the photocurrent responses of Bi24O31Cl10 and Bi24O31Cl10/RhB under monochromatic light at 550 nm. (f) Nyquist impedance plots of Bi24O31Cl10 and Bi24O31Cl10/RhB in the dark and under visible light (λ ≥ 420 nm) conditions.
Mentions: From the de-coloration of RhB over Bi24O31Cl10 submicron platelets in visible light (Figure 4(a)), it was found that the absorptive intensity of RhB at a wavelength of 554 nm gradually decreases. The absorption band shifts to the shorter wavelength of 498 nm. This phenomenon reflects a typical process of photochemical N-de-ethylation of RhB to Rhodamine17. As the reaction time is increased above 75 min, the intensity of the absorption peak of Rhodamine (498 nm) continues to decrease, even though no peak shifting was observed. This indicates that the aromatic chromophore is still attacked by the active species leading to the decomposition of RhB45. This photocatalytic behaviour of Bi24O31Cl10 reflects intense photosensitization activity similar to that of another bismuth oxyhalide, BiOCl46. In order to confirm the photosensitization process in RhB/Bi24O31Cl10, a 300 W Xe lamp with a monochromatic light filter with the pass wavelength of 550 nm (see Supplementary Figure S7) was used for the irradiation light in a photocatalytic measurement, as shown in Figure 4(b) and 4(c). Note that RhB was still degraded, although Bi24O31Cl10 cannot absorb light with a wavelength of 550 nm. We rule out possible physical adsorption because the absorption peaks show an obvious shift during the photocatalytic process which indicates a chemical process. Figure 4(d) shows the fluorescence emission spectra of RhB with and without Bi24O31Cl10. The original RhB solution has a strong fluorescence emission at 580 nm (excited at 532 nm). When Bi24O31Cl10 colloidal suspension was added into the RhB solution, it can be seen that the fluorescence emission is remarkably decreased. The fluorescence quenching indicates that the excited electrons have not gone back to the internal energy level in RhB, instead they are transferred directly from the LUMO of RhB to the CB of Bi24O31Cl1047. This charge transfer was also confirmed by a photocurrent response measurement carried out on the Bi24O31Cl10 and Bi24O31Cl10/RhB samples by using visible light (λ ≥ 420 nm) and monochromatic light (550 nm) irradiation. Figure 4(e) shows a comparison of the photocurrent responses contributed by the Bi24O31Cl10 and Bi24O31Cl10/RhB samples. Bi24O31Cl10/RhB shows a much stronger photocurrent under visible light irradiation. The photocurrent of the Bi24O31Cl10/RhB gradually decreases in the cycling test because of photocatalytic degradation of RhB by Bi24O31Cl10. On the other hand, the Bi24O31Cl10/RhB sample produces obvious photocurrent under monochromatic light irradiation, while the Bi24O31Cl10 does not show any photoresponse. The photoresponse characterizations clearly demonstrate that Bi24O31Cl10 can be sensitized by dye molecules. Finally, the separation of photoinduced electron-hole pairs and charge transfer processes in Bi24O31Cl10/RhB were investigated by typical electrochemical impedance spectroscopy (EIS). The slope of EIS plots can be used to evaluate the efficiency of charge separation and transfer. A smaller slope reflects higher electron-hole separation and transfer efficiencies, and vice versa4849. The EIS Nyquist plot of a Bi24O31Cl10/RhB film on indium tin oxide (ITO) electrodes measured in the dark shows an even smaller slope in contrast to that of Bi24O31Cl10 measured under light irradiation, as displayed in Figure 4(f). This confirms that RhB indeed promotes the separation and transfer processes of photoinduced charge carriers in Bi24O31Cl10/RhB in visible light.

Bottom Line: Density functional theory calculations reveal that the p-block elements determine the nature of the dispersive electronic structures and narrow band gap in Bi24O31Cl10.Bi24O31Cl10 exhibits excellent visible-light photocatalytic activity towards the degradation of Rhodamine B, which is promoted by dye sensitization due to compatible energy levels and high electronic mobility.In addition, Bi24O31Cl10 is also a suitable photoanode material for dye-sensitized solar cells and shows power conversion efficiency of 1.5%.

View Article: PubMed Central - PubMed

Affiliation: Center of Materials Physics and Chemistry and Department of Physics, Beihang University, Beijing 100191, P. R. China.

ABSTRACT
The p-block semiconductors are regarded as a new family of visible-light photocatalysts because of their dispersive and anisotropic band structures as well as high chemical stability. The bismuth oxide halides belong to this family and have band structures and dispersion relations that can be engineered by modulating the stoichiometry of the halogen elements. Herein, we have developed a new visible-light photocatalyst Bi24O31Cl10 by band engineering, which shows high dye-sensitized photocatalytic activity. Density functional theory calculations reveal that the p-block elements determine the nature of the dispersive electronic structures and narrow band gap in Bi24O31Cl10. Bi24O31Cl10 exhibits excellent visible-light photocatalytic activity towards the degradation of Rhodamine B, which is promoted by dye sensitization due to compatible energy levels and high electronic mobility. In addition, Bi24O31Cl10 is also a suitable photoanode material for dye-sensitized solar cells and shows power conversion efficiency of 1.5%.

No MeSH data available.