J. Mater. Sci. Technol. ›› 2018, Vol. 34 ›› Issue (6): 931-941.DOI: 10.1016/j.jmst.2017.09.019
• Orginal Article • Previous Articles Next Articles
Chang Liu, Xiang Zhu, Peng Wang, Yisen Zhao, Yongqing Ma*()
Received:
2017-04-16
Revised:
2017-08-21
Accepted:
2017-09-20
Online:
2018-06-10
Published:
2018-06-05
Contact:
Ma Yongqing
Chang Liu, Xiang Zhu, Peng Wang, Yisen Zhao, Yongqing Ma. Defects and interface states related photocatalytic properties in reduced and subsequently nitridized Fe3O4/TiO2[J]. J. Mater. Sci. Technol., 2018, 34(6): 931-941.
Fig. 1. XRD patterns of standard cards in powder diffraction files (PDF) for Fe3O4 (No.19-0629) (a), samples Fe3O4 (b) and Fe3O4@TiO2 (c) and anatase TiO2 (No. 21-1272) (d).
Fig. 2. TEM (a, d), SEM (b, e) and HRTEM (c, f) images for Fe3O4 (a-c) and TiO2 (d-f); Insets in (c) and (f) show the magnified details of areas 1, 2, 3 and 4 marked with squares.
Fig. 3. Room temperature M(H) loops of Fe3O4 (a) and Fe3O4@TiO2 (b), variation of methylene blue concentration C/C0 with time in presence of Fe2O3@TiO2 catalyst with inset being the magnetic separation photo after degradation (c), linear fitting of degradation process according to pseudo first-order kinetic model (d).
Ae (%) | De (%) | kapp (10-2 min-1) | Ms (emu g-1) | |
---|---|---|---|---|
Fe3O4@TiO2 | 72 | 93.4 | 1.29 | 1.4 |
400 °C | 61 | 87.4 | 1.43 | 1.6 |
600 °C | 55 | 82.5 | 1.01 | 19.7 |
800 °C | 26 | 99.6 | 4.70 | 23.8 |
1000 °C | 10 | 91.6 | 1.55 | 18.2 |
P25 | 2.3 | 99.0 | 4.20 |
Table 1 Adsorption efficiency (Ae), degradation efficiency (De), apparent reaction rate constant kapp and saturation magnetization (Ms) of all magnetic photocatalysts and commercial P25.
Ae (%) | De (%) | kapp (10-2 min-1) | Ms (emu g-1) | |
---|---|---|---|---|
Fe3O4@TiO2 | 72 | 93.4 | 1.29 | 1.4 |
400 °C | 61 | 87.4 | 1.43 | 1.6 |
600 °C | 55 | 82.5 | 1.01 | 19.7 |
800 °C | 26 | 99.6 | 4.70 | 23.8 |
1000 °C | 10 | 91.6 | 1.55 | 18.2 |
P25 | 2.3 | 99.0 | 4.20 |
Fig. 4. XRD patterns of samples synthesized after Fe3O4/TiO2 is reduced in H2/N2 at 400 °C (a), 600 °C (b), 800 °C (c), 1000 °C (d) and commercial P25 (e), standard PDF card of rutile TiO2 (No. 21-1276) (f).
Fig. 5. SEM (a), TEM (b) and HRTEM (c) images for reduced Fe3O4@TiO2 at 800 °C, TEM image of P25 (d); The inset in (c) shows magnified details of area marked with square.
Fe 2p3/2 | O 1s | Ti 2p3/2 | |||||||
---|---|---|---|---|---|---|---|---|---|
Fe3O4@TiO2 | BE (eV) | 710.7 | 712.1 | 707.0 | 530.4 | 530.0 | 532.3 | 458.7 | 460.2 |
CS | Fe2+ | Fe3+ | Fe | TiO2 | Fe-O | Ov | TiO2 | TiOx | |
Ratio (%) | 15 | 85 | 0 | 66.0 | 22.6 | 11.4 | 91.5 | 8.5 | |
800 °C in H2/N2 | BE (eV) | 710.7 | 712.1 | 707.0 | 530.3 | 531.1 | 532.3 | 459.0 | 460.2 |
CS | Fe2+ | Fe3+ | Fe | TiO2 | TiOH | Ov | TiO2 | TiOx | |
Ratio (%) | 36.0 | 61.6 | 2.4 | 72.1 | 14.8 | 13.1 | 88.1 | 11.9 | |
1000 °C in H2/N2 | BE (eV) | 710.7 | 712.1 | 707.5 | 530.3 | 531.1 | 532.4 | 459.1 | 460.2 |
CS | Fe2+ | Fe3+ | Fe | TiO2 | TiOH | Ov | TiO2 | TiOx | |
Ratio (%) | 67.2 | 29.7 | 3.1 | 64.6 | 15.4 | 20.0 | 87.5 | 12.5 |
Table 2 Summary of XPS details of Fe3O4@TiO2 and its reduced samples in H2/N2 at 800 °C and 1000 °C (BE: binding energy).
Fe 2p3/2 | O 1s | Ti 2p3/2 | |||||||
---|---|---|---|---|---|---|---|---|---|
Fe3O4@TiO2 | BE (eV) | 710.7 | 712.1 | 707.0 | 530.4 | 530.0 | 532.3 | 458.7 | 460.2 |
CS | Fe2+ | Fe3+ | Fe | TiO2 | Fe-O | Ov | TiO2 | TiOx | |
Ratio (%) | 15 | 85 | 0 | 66.0 | 22.6 | 11.4 | 91.5 | 8.5 | |
800 °C in H2/N2 | BE (eV) | 710.7 | 712.1 | 707.0 | 530.3 | 531.1 | 532.3 | 459.0 | 460.2 |
CS | Fe2+ | Fe3+ | Fe | TiO2 | TiOH | Ov | TiO2 | TiOx | |
Ratio (%) | 36.0 | 61.6 | 2.4 | 72.1 | 14.8 | 13.1 | 88.1 | 11.9 | |
1000 °C in H2/N2 | BE (eV) | 710.7 | 712.1 | 707.5 | 530.3 | 531.1 | 532.4 | 459.1 | 460.2 |
CS | Fe2+ | Fe3+ | Fe | TiO2 | TiOH | Ov | TiO2 | TiOx | |
Ratio (%) | 67.2 | 29.7 | 3.1 | 64.6 | 15.4 | 20.0 | 87.5 | 12.5 |
Fig. 7. UV-vis diffuse reflectance spectra (DRS) of Fe3O4, Fe3O4@TiO2 and reduced Fe3O4@TiO2 at 400, 600, 800 and 1000 °C and UV-vis DRS of P25 (inset) (a), fitting curves of UV-vis DRS for Fe3O4@TiO2 (b), and reduced Fe3O4@TiO2 at 400 °C (c), 600 °C (d), 800 °C (e) and 1000 °C (f): The black solid line is the experimental curve; The colorful solid lines are the fitting curves. Empty circles are the sum of the fitting curves.
Peak | Fe3O4@TiO2 | Reduction in H2/N2 | |||
---|---|---|---|---|---|
400 °C | 600 °C | 800 °C | 1000 °C | ||
P1 (nm) | 423 | 420 | 429 | 432 | 432 |
P2 (nm) | 492 | 491 | 492 | 493 | 490 |
Table 3 Peak positions in wavelength region of 400-500 nm obtained by fitting the UV-vis spectra.
Peak | Fe3O4@TiO2 | Reduction in H2/N2 | |||
---|---|---|---|---|---|
400 °C | 600 °C | 800 °C | 1000 °C | ||
P1 (nm) | 423 | 420 | 429 | 432 | 432 |
P2 (nm) | 492 | 491 | 492 | 493 | 490 |
Fig. 8. Room temperature M(H) loops of reduced Fe3O4@TiO2 at 400, 600, 800 and 1000 °C (a); Variation of methylene blue concentration C/Ce (empty circles) with time in presence of reduced Fe2O3@TiO2 at 400, 600, 800 and 1000 °C as well as commercial P25 (b), in which the solid lines are the fitting curves according to the pseudo first-order kinetic model; The inset shows the magnetic separation photo after degradation for the 800 °C reduced sample. Variation of methylene blue concentration C/Ce with time in presence of 800 °C reduced Fe2O3@TiO2 during four runs (c). Concentration variation of phenol, C/Ce, with time in the presence of 600 and 800 °C reduced Fe2O3@TiO2 as well as the commercial P25 (d).
Fig. 10. Core level XPS spectra of Fe 2p3/2 (a, d, g), N 1s (b, e, h) and Ti 2p3/2 (c, f, i) for nitridized samples at 500 °C (a-c), 600 °C (d-f) and 700 °C (g-i).
Treated in NH3 | N 1s | Fe 2p3/2 | Ti 2p3/2 | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
500 °C | BE (eV) | 396.7 | 400.8 | 398.3 | 397.3 | 710.8 | 707.8 | 712.1 | 459.1 | 460.2 | 456.7 |
CS | TiN | TiO2-xNx | Fe2N | Fe2+ | Fe2N | Fe3+ | TiO2 | TiOx | TiN | ||
Ratio (%) | 4.5 | 71.8 | 23.5 | 0.2 | 67.0 | 1.3 | 31.7 | 84.1 | 15.9 | 0.0 | |
600 °C | BE (eV) | 396.5 | 400.9 | 398.4 | 397.3 | 710.8 | 707.8 | 712.1 | 459.2 | 460.2 | 456.7 |
CS | TiN | TiO2-xNx | Fe2N | Fe2+ | Fe2N | Fe3+ | TiO2 | TiOx | TiN | ||
Ratio (%) | 34.2 | 48.2 | 15.2 | 2.4 | 70.0 | 1.4 | 28.6 | 99.8 | 0.0 | 0.2 | |
700 °C | BE (eV) | 396.6 | 400.9 | 398.4 | 397.3 | 710.7 | 708.0 | 712.1 | 458.7 | 460.2 | 456.7 |
CS | TiN | TiO2-xNx | Fe2N | Fe2+ | Fe2N | Fe3+ | TiO2 | TiOx | TiN | ||
Ratio (%) | 60.2 | 22.8 | 14.3 | 2.7 | 94.8 | 5.2 | 0.0 | 61.0 | 0.0 | 39.0 |
Table 4 Summary of XPS details of nitridized samples in NH3 at 500 °C, 600 °C and 700 °C.
Treated in NH3 | N 1s | Fe 2p3/2 | Ti 2p3/2 | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
500 °C | BE (eV) | 396.7 | 400.8 | 398.3 | 397.3 | 710.8 | 707.8 | 712.1 | 459.1 | 460.2 | 456.7 |
CS | TiN | TiO2-xNx | Fe2N | Fe2+ | Fe2N | Fe3+ | TiO2 | TiOx | TiN | ||
Ratio (%) | 4.5 | 71.8 | 23.5 | 0.2 | 67.0 | 1.3 | 31.7 | 84.1 | 15.9 | 0.0 | |
600 °C | BE (eV) | 396.5 | 400.9 | 398.4 | 397.3 | 710.8 | 707.8 | 712.1 | 459.2 | 460.2 | 456.7 |
CS | TiN | TiO2-xNx | Fe2N | Fe2+ | Fe2N | Fe3+ | TiO2 | TiOx | TiN | ||
Ratio (%) | 34.2 | 48.2 | 15.2 | 2.4 | 70.0 | 1.4 | 28.6 | 99.8 | 0.0 | 0.2 | |
700 °C | BE (eV) | 396.6 | 400.9 | 398.4 | 397.3 | 710.7 | 708.0 | 712.1 | 458.7 | 460.2 | 456.7 |
CS | TiN | TiO2-xNx | Fe2N | Fe2+ | Fe2N | Fe3+ | TiO2 | TiOx | TiN | ||
Ratio (%) | 60.2 | 22.8 | 14.3 | 2.7 | 94.8 | 5.2 | 0.0 | 61.0 | 0.0 | 39.0 |
Fig. 11. UV-vis DRS of samples nitridized at 500, 600 and 700 °C (a), variation of methylene blue concentration C/Ce (empty symbols) with time in the presence of nitridized samples at 500, 600 and 700 °C (b), in which the solid lines are the fitting curves according to the pseudo first-order kinetic model, room temperature M(H) loops of nitridized samples at 500, 600 and 700 °C (c).
Nitridized in NH3 | Ae (%) | De (%) | kapp (10-2 min-1) |
---|---|---|---|
500 °C | 12.7 | 99.7 | 2.5 |
600 °C | 16.1 | 99.8 | 3.5 |
700 °C | 18.2 | 75.8 | 0.8 |
Table 5 Adsorption efficiency (Ae), degradation efficiency (De) and apparent reaction rate constant kapp of all nitridized photocatalysts.
Nitridized in NH3 | Ae (%) | De (%) | kapp (10-2 min-1) |
---|---|---|---|
500 °C | 12.7 | 99.7 | 2.5 |
600 °C | 16.1 | 99.8 | 3.5 |
700 °C | 18.2 | 75.8 | 0.8 |
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