以錫修飾白金電極對一氧化碳感測之研究

• Main Author: 王瓊紫
• Other Authors: 楊明長
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/80930004696528312040

碩士 === 國立成功大學 === 化學工程學系 === 88 === Carbon monoxide, a product of incomplete oxidation of fuels, is very hazardous to human. When using elemental metal for the catalyst of a sensing electrode, there is still space to improve the sensitivity, selectivity and stability of electrochemical CO sensor. In this study, Pt/Nafion electrodes were prepared by impregnation-reduction method, and tin was then electrodeposited onto platinum to form Sn/Pt/Nafion electrode. The effects of preparation conditions on the sensitivity of modified electrodes were then studied. A typical Pt/Nafion electrode was prepared with impregnation in 0.02 M Pt(NH3)4Cl2 at 40 oC for 2 hrs, then reduction in 0.2 M NaBH4, dissolved in pH 11 NaOH, at 40 oC for 30 min. The sensitivity was found to be 0.34 μA/ppm CO for Pt/Nafion electrode in sensing CO below 1000 ppm. In this study, cyclic voltammetry was used to renew electrodes before sensing CO. This renewal method worked well for both Sn/Pt/Nafion and Pt/Nafion electrodes. After Pt/Nafion preparation, tin was then electro- deposited onto Pt. The typical condition was 0.1 M SnCl4/3 M H2SO4 at 0 V (vs. Ag/AgCl) for 30 min to prepare Sn/Pt/Nafion electrodes. No limiting current was found for Sn/Pt/Nafion electrode during sensing CO below 1000 ppm. Sensitivities are different in sensing 0~250 and 250~1000 ppm CO. With the typical preparation condition as mentioned, the sensitivity in the range of 250~1000 ppm was 2.8 times of that for Pt/Nafion electrode; the sensitivity in the range of 0~100 ppm was 8.5 times of that for Pt/Nafion electrode. The effects of impregnation time and pH of NaOH on the sensitivities of Sn/Pt/Nafion electrodes were studied. With Pt/Nafion electrode prepared with impregnation for 2 hr, then reduction in 0.2 M NaBH4, dissolved in pH 11 NaOH, higher sensitivity was obtained after tin modification. The effects of electrodeposition conditions on the sensitivities of Sn/Pt/Nafion electrodes were studied. Sn/Pt/NafionR prepared with electrodepostion in 0.1 M SnCl4/3 M H2SO4 for 1 hr, higher sensitivity was obtained at applied potential between —0.05 to 0.05 V (vs. Ag/AgCl). When Sn/Pt/NafionR was prepared with electrodeposition in 0.001~0.1 M SnCl4/3 M H2SO4at 0 V (vs. Ag/AgCl) for 1 hr, the sensitivity in the 250~1000 ppm range was 0.7 μA/ppm CO. The sensitivity in the 0~100 ppm range slightly increased with increasing concentration of deposition solution. With Sn/Pt/NafionR prepared with electrodeposition in 0.1 M SnCl4/3 M H2SO4 at 0 V (vs. Ag/AgCl), deposition time from 30 sec to 1 hr, the sensitivity in the range of 250~1000 ppm was highest with 30 min deposition time, which was 0.95 μA/ppm CO, 2.8 times of that for Pt/Nafion electrode. The sensitivity in the range of 0~100 ppm was higher with 5~30 min deposition time; it was 2.90 μA/ppm CO, 8.5 times of that for Pt/Nafion electrode, with 30 min deposition time.