Visible Photocatalytic Activity Enhancement of ZnWO4 by Graphene ...
Visible Photocatalytic Activity Enhancement of ZnWO4 by Graphene Hybridization Xiaojuan Bai, Li Wang, Yongfa Zhu* Department of Chemistry, Tsinghua University, Beijing 10084, P. R. China Corresponding author: E-mail: [email protected]; Fax: +86-10-62787601; Tel: +86-10-62787601.
Graphene Oxide (GO) The details are described as follows. Graphite (3.0g) was added to concentrated sulfuric acid (70mL) under stirring at room temperature, then sodium nitrate (1.5g) was added, and the mixture was cooled to 0oC. Under vigorous agitation, potassium permanganate (9.0g) was added slowly to keep the temperature of the suspension lower than 20oC. Successively, the reaction system was transferred to a 35 ±5oC water bath and stirred for about 0.5h, forming a thick paste. Then, 150ml of water was added, and the solution was stirred for 15min at 90±5 oC. Additional 500mL of water was added and followed by a slow addition of 15mL of H2O2 (3%), turning the color of the solution from dark brown to yellow. The mixture was filtered and washed with 1:10 HCl aqueous solution (250ml) to remove metal ions followed by washing with 200ml of water to remove the acid. The resulting solid was dried in air and diluted to make a GO aqueous dispersion (0.5% w/w). Finally, it was purified by dialysis for one week to remove the remaining metal species.
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Reduction of GO 100 mg of graphene oxide (GO) was dispersed in 50 ml of solvent by sonication for 0.5 h and the brown colloidal dispersion was transferred to a stainless steel autoclave and sealed, heated in oven at 180 oC for 24h.
Figure S1. Apparent rate constants for the photodegradation of MB over ZnWO4 and ZnWO4/graphene photocatalysts (a) under visible light irradiation (λ>420nm, [MB]=0.01mM). (b) under UV light irradiation (λ=254nm, [MB]=0.03mM).
Figure S2. TEM images of (a) ZnWO4 and (b) GZW0.2 nanords.
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Figure S3. N2 adsorption-desorption isotherms and Barret-Joyner-Halenda (BJH) (inset) pore size distribution plots of ZnWO4 and ZnWO4/graphene photocatalysts.
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Figure S4. (a, b, c) FTIR spectra of ZnWO4 and ZnWO4/graphene photocatalysts.
Figure S5. XRD patterns of ZnWO4 and ZnWO4/graphene photocatalysts.
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Figure S6. XPS spectra for ZnWO4/graphene samples: (a) wide spectra, (b) W4f.
Figure S7. Changes of MB concentration in ZnWO4 and GZW0.2 photocatalytic system in dark.
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Figure S8. Photostability experiments for photocatalytic degradation of MB over GZW0.2 photocatalyst. (MB=3×10-5 mol/L, λ>420 nm, light intensity 40mW/cm2).
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Table 1. The standard error data of apparent rate constants k for the photodegradation of MB over ZnWO4 and ZnWO4/graphene photocatalysts under visible light irradiation (λ>420nm, [MB]=0.01mM).
k
Value
Standard error
Adj.R-Square
P25 GMW0.2 ZnWO4 GZW0.004 GZW0.02 GZW0.05 GZW0.2 GZW0.8 GZW2.0 Blank Dark
0.3178 0.2925 0.0676 0.2543 0.293 0.3264 0.4824 0.3273 0.2849 0.0676 0.0257
0.0241 0.0102 0.0024 0.0069 0.0096 0.0179 0.0295 0.0225 0.0244 0.0024 0.0021
0.9718 0.9939 0.9936 0.9963 0.9946 0.985 0.9815 0.9768 0.9643 0.9936 0.9673
sample
Table 2. The standard error data of apparent rate constants k for the photodegradation of MB over ZnWO4 and ZnWO4/graphene photocatalysts under UV light irradiation (λ=254nm, [MB]=0.03mM). k sample P25 GMW0.2 ZnWO4 GZW0.004 GZW0.02 GZW0.05 GZW0.2 GZW0.8 GZW2.0 Blank Dark
Value
Standard error
Adj.R-Square
0.01532 0.00383 0.00729 0.00768 0.00822 0.01011 0.017 0.00593 0.00479 2.10E-06 3.48E-05
7.98E-04 1.05E-04 4.47E-04 1.66E-04 2.05E-04 9.65E-05 2.32E-04 3.22E-04 3.41E-04 8.70E-05 3.90E-05
0.9866 0.9962 0.9815 0.9976 0.9969 0.9995 0.999 0.9854 0.9751 -0.2498 -0.0421
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Graphene Oxide (GO) The details are described as follows. Graphite (3.0g) was added to concentrated sulfuric acid (70mL) under stirring at room temperature, then sodium nitrate (1.5g) was added, and the mixture was cooled to 0oC. Under vigorous agitation, potassium permanganate (9.0g) was added slowly to keep the temperature of the suspension lower than 20oC. Successively, the reaction system was transferred to a 35 ±5oC water bath and stirred for about 0.5h, forming a thick paste. Then, 150ml of water was added, and the solution was stirred for 15min at 90±5 oC. Additional 500mL of water was added and followed by a slow addition of 15mL of H2O2 (3%), turning the color of the solution from dark brown to yellow. The mixture was filtered and washed with 1:10 HCl aqueous solution (250ml) to remove metal ions followed by washing with 200ml of water to remove the acid. The resulting solid was dried in air and diluted to make a GO aqueous dispersion (0.5% w/w). Finally, it was purified by dialysis for one week to remove the remaining metal species.
S1
Reduction of GO 100 mg of graphene oxide (GO) was dispersed in 50 ml of solvent by sonication for 0.5 h and the brown colloidal dispersion was transferred to a stainless steel autoclave and sealed, heated in oven at 180 oC for 24h.
Figure S1. Apparent rate constants for the photodegradation of MB over ZnWO4 and ZnWO4/graphene photocatalysts (a) under visible light irradiation (λ>420nm, [MB]=0.01mM). (b) under UV light irradiation (λ=254nm, [MB]=0.03mM).
Figure S2. TEM images of (a) ZnWO4 and (b) GZW0.2 nanords.
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Figure S3. N2 adsorption-desorption isotherms and Barret-Joyner-Halenda (BJH) (inset) pore size distribution plots of ZnWO4 and ZnWO4/graphene photocatalysts.
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Figure S4. (a, b, c) FTIR spectra of ZnWO4 and ZnWO4/graphene photocatalysts.
Figure S5. XRD patterns of ZnWO4 and ZnWO4/graphene photocatalysts.
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Figure S6. XPS spectra for ZnWO4/graphene samples: (a) wide spectra, (b) W4f.
Figure S7. Changes of MB concentration in ZnWO4 and GZW0.2 photocatalytic system in dark.
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Figure S8. Photostability experiments for photocatalytic degradation of MB over GZW0.2 photocatalyst. (MB=3×10-5 mol/L, λ>420 nm, light intensity 40mW/cm2).
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Table 1. The standard error data of apparent rate constants k for the photodegradation of MB over ZnWO4 and ZnWO4/graphene photocatalysts under visible light irradiation (λ>420nm, [MB]=0.01mM).
k
Value
Standard error
Adj.R-Square
P25 GMW0.2 ZnWO4 GZW0.004 GZW0.02 GZW0.05 GZW0.2 GZW0.8 GZW2.0 Blank Dark
0.3178 0.2925 0.0676 0.2543 0.293 0.3264 0.4824 0.3273 0.2849 0.0676 0.0257
0.0241 0.0102 0.0024 0.0069 0.0096 0.0179 0.0295 0.0225 0.0244 0.0024 0.0021
0.9718 0.9939 0.9936 0.9963 0.9946 0.985 0.9815 0.9768 0.9643 0.9936 0.9673
sample
Table 2. The standard error data of apparent rate constants k for the photodegradation of MB over ZnWO4 and ZnWO4/graphene photocatalysts under UV light irradiation (λ=254nm, [MB]=0.03mM). k sample P25 GMW0.2 ZnWO4 GZW0.004 GZW0.02 GZW0.05 GZW0.2 GZW0.8 GZW2.0 Blank Dark
Value
Standard error
Adj.R-Square
0.01532 0.00383 0.00729 0.00768 0.00822 0.01011 0.017 0.00593 0.00479 2.10E-06 3.48E-05
7.98E-04 1.05E-04 4.47E-04 1.66E-04 2.05E-04 9.65E-05 2.32E-04 3.22E-04 3.41E-04 8.70E-05 3.90E-05
0.9866 0.9962 0.9815 0.9976 0.9969 0.9995 0.999 0.9854 0.9751 -0.2498 -0.0421
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