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Table 2 Some doped-elements, preparation methods, and the doping effects of doped titania nanotubes as based on the classification of metal-doping, non-metal doping, and co-doping

From: A Review on the Electrochemically Self-organized Titania Nanotube Arrays: Synthesis, Modifications, and Biomedical Applications

Classification Raw material Synthesis Element Doping effect Ref
Metal doping K3Fe(CN)6 One-step anodizing
60 V 6 h at 25 °C
Fe Band gap: 2.85/2.65/2.10/2.03 eV (undoped: 3.18 eV) photocurrent density: 930/1320/675/590 μA cm−2
(undoped: < 240 μA cm− 2) at 1.5 V under visible light more stable and high photoresponse to visible light
[108]
Cu(NO3)2·3H2O One-step anodizing
20 V 1 h at room temperature
Cu Band gap: 2.65 eV (undoped: 3.20 eV) total amount of H2 evolved: 29 μL cm−2 2 h (undoped: 7.6 μL cm− 2 2 h) higher decomposition rate of methylene blue higher stability after multiple reuses [109]
K2CrO4 One-step anodizing
60 V 6 h
at 25 °C
Cr Band gap: 2.82/2.71/2.30 eV (undoped: 3.20 eV) photocurrent density: 360/280/190 μA cm−2
(undoped: < 39 μA cm− 2) at 1.0 V under visible light total amount of H2 evolved: 37/28/12 μL cm− 2 4 h (undoped: ≈ 0 μL cm−2) higher stability after multiple reuses
[110]
Zr(NO3)4 Two-step anodizing
3/7/10/15 V 1 h
Zr Higher photocatalytic activities than that of pure TiO2 nanotube arrays good photocatalytic stability and could be reused [111]
ZnF2 One-step anodizing 30 V 15 h
at 25 °C
Zn Band gap: 2.86/2.84 eV (undoped: 3.00 eV) degeneration rate of methylene blue under visible light for 10 h:88/66% (undoped: ≈ 62%) [112]
V2O5 One-pot hydrothermal method at 130 °C 3 h V Band gap: 2.91 eV (undoped: 3.18 eV) increased photocurrent density reaction rate (Kapp)of rhodamine B: 3 ~ 9 fold as compared to undoped one under UV and visible light [113]
Non-metal doping NH3 Annealing a flow rate of 400 mL min−1 at 500 °C 3 h N Band gap: 2.8 eV (undoped: 3.1 eV) Table2: Some doped-elements, preparation methods, and the doping effects of doped titania nanotubes as a based on the classification of metal-doping, non-metal doping, and co-doping. Table 2: Some doped-elements, preparation methods, and the doping effects of doped titania nanotubes as a based on the classification of metal-doping, non-metal doping, and co-doping. Photocurrent density: 1.4 mA cm−2 (undoped: 1.6 mA cm− 2) at 0.9 V under UV-enhanced PEC activities under visible light and decreased UV light absorption [105]
H2TiF6 Spray pyrolysis F Enhancement of surface acidity and creation of oxygen vacancies, increase of active sites [114]
H3BO3 Anodizing 1.8 V
15-60 min
B Band gap: 2.91 eV (undoped: 3.20 eV), photocurrent density: 311 μA cm−2 (undoped: 41.7 μA cm−2) at − 0.6 ~ 0.9 V under UV [115]
CH4 Calcination at 820 °C 18 min in natural gas flame C Band gap: 2.84 eV (undoped: 2.92 eV) an additional intragap band: 1.30 eV increased lifetime of photogenerated carriers in the UV [116]
K2S2O5 One-step anodizing 20 V 1 h at 25 °C S Band gap: 2.61 eV (undoped: 3.20 eV) high stability after multiple reuses photocurrent density: > 1.22 mA cm−2 (undoped:< 0.19 mA cm−2) at 1.50 V under visible light total amount of H2 evolved: 41 μL cm−2 4 h (undoped: ≈ 0 μL cm−2) [117]
KI、HIO4 Two-step anodizing 1.5 V 15 min
at 23 ± 1 °C
I Band gap: 2.95/3.0 eV (undoped: 3.07 eV) enhanced photocurrent density under both visible and UV illumination degeneration rate of methylene blue under visible light for 2 h: 71/65% (undoped: ≈ 31%) [118]
Co-doping NH3
TaCl5
Drop-casting method
at 450 °C 30 min
N-Ta Band gap: 2.5 eV (undoped: 3.1 eV) photocurrent density: 2.5 mA cm−2 (undoped: 1.6 mA cm−2) at 0.9 V under UV-enhanced PEC activities under both visible and UV illumination [105]
NH3
(NH4)5[(NbOF4)(NbF7)2]
Anodizing 45 V at 25 ± 1 °C annealing a flow rate of 100cm3 min−1 at 550 °C 2 h N-Nb Strongly enhanced PEC activities for water splitting under both visible light and UV light [107]
K2[Ni(CN)4] Anodizing 40 V 2 h at room temperature Ni-N-C Band gap: 2.588 ~ 2.972 eV (undoped: 3.062 eV) photocurrent density: 10 times greater than that of undoped one under visible light [119]