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Polyoxometalates (POMs, such as Keggin-type and Dawson-type) and the electrochemical copolymerization with aniline is an important method for preparing functional conductive composite materials. The product combines the redox activity of POMs and the conductivity of polyaniline (PANI), and can be used in catalysis, sensing, energy storage and other fields. The following are the detailed experimental methods and key precautions:
First, prepare the materials and equipment:
Polyoxometalates (POMs) commonly used POMs: phosphomolybdic acid (H₃PMo₁₂O₄₀), silicon tungstic acid (H₄SiW₁₂O₄₀), etc., need to be purified before use, solubility: POMs are usually soluble in water or polar organic solvents (such as acetonitrile).
Aniline monomer: need to be distilled purified (remove oxidized impurities), store in the dark.
Support electrolyte: acidic medium: 0.1–1 M H₂SO₄ (promotes aniline polymerization and POMs stability). Non-aqueous system: LiClO₄/acetone (suitable for hydrophobic POMs).
Electrode system
Working electrode: ITO glass, platinum sheet or carbon electrode (needs polishing and cleaning).
Counter electrode: platinum wire or graphite rod.
Reference electrode: Ag/AgCl (aqueous phase) or Ag/Ag⁺ (non-aqueous phase).
Copolymerization method:
Solution preparation
1) Aqueous phase system:
0.1 M aniline + 1–10 mM POMs + 0.5 M H₂SO₄ (pH ~1).
The POMs concentration needs to be optimized (too high may cause precipitation).
Organic phase system:
0.1 M aniline + 5 mM POMs + 0.1 M LiClO₄/acetone (requires anhydrous operation).
2) Electro polymerization technology
Cyclic Voltammetry (CV) (most commonly used):
Potential range: -0.2 V → +0.8–1.0 V (vs. Ag/AgCl).
Scan rate: 20–50 mV/s, cycle 10–20 times.
Constant potential method: apply a constant potential (such as +0.8 V), until the charge quantity reaches the target value (usually 1–10 mC/cm²).
Constant current method: current density: 0.1–0.5 mA/cm², time 10–30 minutes.
