Ozone reduction at Nafion modified Au electrode and the measurement of ozone concentration in highly resistive solutions

The mass transport and charge transfer kinetics of ozone reduction at Nafion coated Au electrodes were studied in 0.5 mol/L H₂SO₄ and highly resistive solutions such as distilled water and tap water. The diffusion coefficient and partition coefficient of ozone in Nafion coating are 1.78×10⁻⁶ cm²·s^−l and 2.75 at 25°C (based on dry state thickness), respectively. The heterogeneous rate constants and Tafel slopes for ozone reduction at bare Au are 4.1×10⁻⁶ cm·s⁻¹, 1.0×10⁻⁶ cm·s⁻¹ and 181 mV, 207 mV in 0.5 mol/L H₂SO₄ and distilled water respectively and the corresponding values for Nafion coated Au are 5.5×10⁻⁶ cm·s^−l, 1,1×10⁻⁶ cm·s⁻¹ and 182 mV, 168 mV respectively. The Au microelectrode with 3 μm Nafion coating shows good linearity over the range 0–10 mmol/L ozone in distilled water with sensitivity 61 μA·ppm⁻¹·cm⁻², detection limit 10 ppb and 95% response time below 5 s at 25°C. The temperature coefficient in range of 11–30°C is 1.3%.