Review Article
Fabrication, Modification, and Emerging Applications of TiO2 Nanotube Arrays by Electrochemical Synthesis: A Review
Table 1
Brief summary of various synthesis generations of TNAs.
| Generation | Electrolyte type | Potential | Anodized time | Morphology | Main Factor | Reference |
| First generation: inorganic aqueous electrolytes (HF-based electrolyte) | 0.5 wt% HF | 10–23 V | ≥20 min | Short nanotubes Length: 200–500 nm Diameter: 10–100 nm Wall thickness: 13–27 nm |
Potential, electrolyte | [13] | 0.3–0.5 wt% HF + 1 M H3PO4 | 1–25 V | 2 h | Length: 20–1000 nm Diameter: 15–120 nm Wall thickness: 20 nm | [32] | Second generation: buffered electrolytes (F−-based electrolytes) | 1 M Na2SO4 + 0.1–1.0 wt% NaF | 20 V | 10 min–6 h | Roughwall with rings Length: 0.5–2.4 μm Diameter: 100 nm Wall thickness: nm |
Potential, pH, time | [28] | 1 M (NH4)2SO4 + 0.5 wt% NH4F | 20 V | 15–30 min | Length: 0.5–1.0 μm Diameter: 90–110 nm | [33] | Third generation: organic electrolyte containing F− ions | 0.5 wt% NH4F + 0–5 wt% H2O in glycerol | 20 V | 13 h | Smooth tube Length: 7.0 μm Diameter: ≈40 nm Wall thickness: nm |
Potential, water content, time | [17] | 0.1–0.7 wt% NH4F + 2–3.5 wt% H2O in ethylene glycol | 60 V | 216 h | Ultra-long tube Length: 1000 μm Diameter: nm | [22] | Fourth generation: fluoride-free electrolytes | 0.01–3 M HClO4 | 1 min | 15–60 V | Disordered tubes Length: 30 μm Diameter: 20–40 nm Wall thickness: 10 nm | Electrolyte, time | [30] |
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