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 diffus ion coefficient and partition coefficient of ozone in Nafion coating a re 1.78x10(-6) cm(2.).s(-1) and 2.75 at 25 degrees C (based on dry sta te thickness), respectively. The heterogeneous rate constants and Tafe l slopes for ozone reduction at bare Au are 4.1x10(-6) cm.s(-1), 1.0x1 0(-6) cm.s(-1) and 181 mV, 207 mV in 0.5 mol/L H2SO4 and distilled wat er respectively and the corresponding values for Nafion coated Au are 5.5x10(-6) cm.s(-1), 1.1x10(-6) cm.s(-1) and 182 mV, 168 mV respective ly. The Au microelectrode with 3 mu m Nafion coating shows good linear ity over the range 0-10 mmol/L ozone in distilled water with sensitivi ty 61 mu A.ppm(-1).cm(-2), detection limit 10 ppb and 95% response tim e below 5 s at 25 degrees C. The temperature coefficient in range of 1 1-30 degrees C is 1.3%.