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Synergic Effect between Adsorption and Photocatalysis of Metal-Free g-C3N4 Derived from Different Precursors.

Xu HY, Wu LC, Zhao H, Jin LG, Qi SY - PLoS ONE (2015)

Bottom Line: After 120 min reaction time, the blue color of MB solution disappeared completely.Subsequently, based on the measurement of the surface Zeta potentials of CN-M500 at different pHs, an active anionic dye, Methyl Orange (MO) was selected as the contrastive target pollutant with MB to reveal the synergic effect between adsorption and photocatalysis.Finally, the photocatalytic mechanism was discussed.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Engineering, Harbin University of Science and Technology, Harbin, P. R. China.

ABSTRACT
Graphitic carbon nitride (g-C3N4) used in this work was obtained by heating dicyandiamide and melamine, respectively, at different temperatures. The differences of g-C3N4 derived from different precursors in phase composition, functional group, surface morphology, microstructure, surface property, band gap and specific surface area were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-visible diffuse reflection spectroscopy and BET surface area analyzer, respectively. The photocatalytic discoloration of an active cationic dye, Methylene Blue (MB) under visible-light irradiation indicated that g-C3N4 derived from melamine at 500°C (CN-M500) had higher adsorption capacity and better photocatalytic activity than that from dicyandiamide at 500°C (CN-D500), which was attributed to the larger surface area of CN-M500. MB discoloration ratio over CN-M500 was affected by initial MB concentration and photocatalyst dosage. After 120 min reaction time, the blue color of MB solution disappeared completely. Subsequently, based on the measurement of the surface Zeta potentials of CN-M500 at different pHs, an active anionic dye, Methyl Orange (MO) was selected as the contrastive target pollutant with MB to reveal the synergic effect between adsorption and photocatalysis. Finally, the photocatalytic mechanism was discussed.

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XPS spectra of CN-M500 and CN-D500.(a) survey (b) C1s (c) N1s, (d) O1s.
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pone.0142616.g006: XPS spectra of CN-M500 and CN-D500.(a) survey (b) C1s (c) N1s, (d) O1s.

Mentions: XPS spectra of CN-M500 and CN-D500 are shown in Fig 6. The wide-scan XPS spectra (Fig 6(a)) reveal that these two samples predominantly contain C and N elements with small amount of O element that might be attributed to the absorbed O2 and H2O or pyrolysis of the precursor in air. The atomic ratios of N/C for both samples were estimated to be 1.17 from the XPS results, a little less than the stoichiometric value. The C1s spectra in Fig 6(b) indicate that, for CN-M500, the C1s region can be fitted into two peaks, ascribed to a carbon-containing contamination (284.6 eV) and sp2-hybridized carbon in the aromatic ring (288.1 eV) [40]; while for CN-D500, the deconvoluted four peaks can be observed and other two peaks are assigned to C-(N)3 (286.2 eV) and N-C-O (291.4 eV) [33]. The formation of C-(N)3 and N-C-O bonds in CN-D500 might be attributed to the incomplete polycondensation of dicyandiamide precursor and redundant step for dicyandiamide to form g-C3N4. In the N1s spectra (Fig 6(c)), the main fitted peak at 398.5 eV shows the existence of sp2-hybridized nitrogen in C-N bonds in both samples [38]. The fitted peak at 399.9 eV in CN-M500 can be assigned to tertiary nitrogen N-(C)3 groups [33], and the peak at 400.8 eV in CN-D500 corresponds to -NH2 or = NH groups [40]. This difference also testifies the incomplete polycondensation of dicyandiamide precursor to form g-C3N4. The deconvoluted three peaks in the O1s spectra (Fig 6(d)) reveal the coexistence of chemisorbed H2O, O-C-N bonds and hydroxyl groups on the surface of both samples [33].


Synergic Effect between Adsorption and Photocatalysis of Metal-Free g-C3N4 Derived from Different Precursors.

Xu HY, Wu LC, Zhao H, Jin LG, Qi SY - PLoS ONE (2015)

XPS spectra of CN-M500 and CN-D500.(a) survey (b) C1s (c) N1s, (d) O1s.
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Related In: Results  -  Collection

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pone.0142616.g006: XPS spectra of CN-M500 and CN-D500.(a) survey (b) C1s (c) N1s, (d) O1s.
Mentions: XPS spectra of CN-M500 and CN-D500 are shown in Fig 6. The wide-scan XPS spectra (Fig 6(a)) reveal that these two samples predominantly contain C and N elements with small amount of O element that might be attributed to the absorbed O2 and H2O or pyrolysis of the precursor in air. The atomic ratios of N/C for both samples were estimated to be 1.17 from the XPS results, a little less than the stoichiometric value. The C1s spectra in Fig 6(b) indicate that, for CN-M500, the C1s region can be fitted into two peaks, ascribed to a carbon-containing contamination (284.6 eV) and sp2-hybridized carbon in the aromatic ring (288.1 eV) [40]; while for CN-D500, the deconvoluted four peaks can be observed and other two peaks are assigned to C-(N)3 (286.2 eV) and N-C-O (291.4 eV) [33]. The formation of C-(N)3 and N-C-O bonds in CN-D500 might be attributed to the incomplete polycondensation of dicyandiamide precursor and redundant step for dicyandiamide to form g-C3N4. In the N1s spectra (Fig 6(c)), the main fitted peak at 398.5 eV shows the existence of sp2-hybridized nitrogen in C-N bonds in both samples [38]. The fitted peak at 399.9 eV in CN-M500 can be assigned to tertiary nitrogen N-(C)3 groups [33], and the peak at 400.8 eV in CN-D500 corresponds to -NH2 or = NH groups [40]. This difference also testifies the incomplete polycondensation of dicyandiamide precursor to form g-C3N4. The deconvoluted three peaks in the O1s spectra (Fig 6(d)) reveal the coexistence of chemisorbed H2O, O-C-N bonds and hydroxyl groups on the surface of both samples [33].

Bottom Line: After 120 min reaction time, the blue color of MB solution disappeared completely.Subsequently, based on the measurement of the surface Zeta potentials of CN-M500 at different pHs, an active anionic dye, Methyl Orange (MO) was selected as the contrastive target pollutant with MB to reveal the synergic effect between adsorption and photocatalysis.Finally, the photocatalytic mechanism was discussed.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Engineering, Harbin University of Science and Technology, Harbin, P. R. China.

ABSTRACT
Graphitic carbon nitride (g-C3N4) used in this work was obtained by heating dicyandiamide and melamine, respectively, at different temperatures. The differences of g-C3N4 derived from different precursors in phase composition, functional group, surface morphology, microstructure, surface property, band gap and specific surface area were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-visible diffuse reflection spectroscopy and BET surface area analyzer, respectively. The photocatalytic discoloration of an active cationic dye, Methylene Blue (MB) under visible-light irradiation indicated that g-C3N4 derived from melamine at 500°C (CN-M500) had higher adsorption capacity and better photocatalytic activity than that from dicyandiamide at 500°C (CN-D500), which was attributed to the larger surface area of CN-M500. MB discoloration ratio over CN-M500 was affected by initial MB concentration and photocatalyst dosage. After 120 min reaction time, the blue color of MB solution disappeared completely. Subsequently, based on the measurement of the surface Zeta potentials of CN-M500 at different pHs, an active anionic dye, Methyl Orange (MO) was selected as the contrastive target pollutant with MB to reveal the synergic effect between adsorption and photocatalysis. Finally, the photocatalytic mechanism was discussed.

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