Amperometric Ammonia sensor - The Preparation of Sensing Electrode and Sensing Characteristic
| Autor: | Yen-Yu Liu, 劉彥妤 |
|---|---|
| Rok vydání: | 2003 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 91 Ammonia sensor plays an important role in the applications of industrial process, environmental sensing and control and medical engineering. For example, the concentration of ammonia in the environment must be controlled under 1 ppm, and monitoring the concentration of ammonia in the breath of human (1~2 ppm) can be used to indirectly diagnose the end-stage renal disease. In this thesis, Pt and Pt-Ir with high electrochemical activity were prepared on Pt (sputtering)/porous ceramic plate by the electroplating controlled at potentiostate. The amperometric ammonia sensor based on the preparing Pt (electroplating)/Pt (sputtering)/porous ceramic plate and Pt-Ir (electroplating) /Pt (sputtering)/porous ceramic plate as sensing electrodes was also assembled to detect the low concentration of ammonia in the liquid and gas phases, respectively. The characteristics of the prepared sensing electrodes, the sensing properties and the aging phenomena and mechanisms of the sensing electrodes were also investigated in this work. In the liquid phase, with the Pt (electroplating) / Pt (sputtering) / porous ceramic plate as sensing electrode, the sensitivity and the response time of the amperometric ammonia sensor for monitoring 0 ~ 186.6 ppm NH3 in 1.0 M KOH solution were obtained to be 8.3 μA ppm-1cm-2 and 1min, respectively, when the agitation rate was controlled at 300 rpm at room temperature. Using the Pt-Ir (2.1:1) (electroplating) / Pt (sputtering) / porous ceramic plate as working electrode, the sensitivity and the response time were found to be 7.8μA ppm-1cm-2 and 2min, respectively, in the same conditions as described above. The sensitivity of amperometric ammonia sensor based on Pt-Ir (2.1:1) (electroplating)/Pt (sputtering)/porous ceramic plate was higher than that of Pt (electroplating)/Pt (sputtering)/porous ceramic plate for the sensing system in the gas phase. Using Pt-Ir (electroplating) / Pt (sputtering) / porous ceramic plate as electrode, the sensitivity and the response time of the amperometric ammonia gas sensor were 1.14μA ppm-1cm-2 and 5 min, respectively, for the concentration of ammonia in the range of 0 ~ 9 ppm at 0% R.H., and in the same concentration range of ammonia, the sensitivity and the response time were increased to 12.06μA ppm-1cm-2 and 24 min, respectively, for increasing the relative humidity to 97 ~ 98%. The sensitivity of the amperometric NH3 gas sensor in the relative humidity of 97 ~ 98% was 10.6 times greater than that of 0% relative humidity. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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