氧化銥/五氧化二鉭電位式二氧化碳感測器抗干擾之研究

Abstract

中 文 摘 要

本實驗所製作出來的電位式二氧化碳感測元件是以濺鍍氧化銥薄膜來當做動作電極且為了抵抗氧氣干擾感測元件的電訊號，所以在氧化銥薄膜上再濺鍍上一層五氧化二鉭薄膜，並且利用PVA•KHCO3來做成固態型電解質薄膜。再者，一般固態電解質裡面的氫離子導電度會比液態電解質來的低，是因為氫離子在固態電解質的移動較困難以及活性較低有關。而整個感測機制是類似濃度電池ㄧ樣。此實驗是以氧化銥薄膜微電極的電位會隨著固態電解質中酸鹼性的變化而改變的觀念來製作感測器。過渡金屬氧化物氧化銥的電位對pH變化大約為58mV/pH。並且藉由動作薄膜電極與標準電極之間的電位差會跟氣體濃度的對數值成正比關係式，因此可以求的混合氣體中二氧化碳濃度。本二氧化碳感測器在1 atm，298K 下工作，對二氧化碳濃度在1 ~ 50% 之間，可以有良好的線性與可逆性反應。並在快速小流量注射實驗中對感測元件注射0.1 ml的二氧化碳氣體時有快速的反應能力，其反應時間為0.4秒。為了改善氧化銥感測元件會受到氧氣干擾缺點，所以本研究發現若多濺鍍ㄧ層五氧化二鉭薄膜的方式來當作氣體抵抗層。不但對感測能力沒有影響，而且有效的改良先前會受到氧氣干擾訊號的問題。

Abstract

Potentiometric microsensors sensitive to carbon dioxide made in the experimentation is used by sputtering iridium oxide thin film as moving plate. In order to resist against O2 to bother signals of sensitive device, we sputter a layer of tantalum oxide lamella upon the lamella of iridium oxide again and take advantage of PVA•KHCO3 to make a layer of solid-electrolyte pellicle. Moreover, the intrinsic conductivity of hydrogen ion inside common solid electrolyte is lower than one of hydrogen ion inside liquid electrolyte. This is because hydrogen ion move to each other more difficult inside solid electrolyte and their activity is also lower. And the mechanism of whole sensor is just similar to concentration cell.

We apply the concept; electric potential of iridium oxide thin film micro-electrode will change with the diversification of acidity or alkaline inside solid electrolyte, to create the sensor. The electric potential of transition metal oxide- iridium oxide for the change of pH value is about 58mV/pH. According to the relation formula, potential difference between motion lamella electrode and standard electrode will be direct proportion to logarithm of gaseous concentration, so we can see the concentration of CO2 in adulterant gas.

The sensor of CO2, worked in the level of 1 atm, 298K for concentration of CO2 between 1-50%, can show favorable linear and reversible reaction. And in rapid hypo-flow injection experiment, when injecting 0.1ml CO2 into sensitive device, we can find it sometimes shows instant reaction and its period is 0.4 seconds. To improve the disadvantageous factor from iridium oxide sensitive device disturbed by CO2, the research concludes that if sputtering a layer of tantalum oxide lamella to against gas layer, it is not only no influence to detect, but also benefit to improve the problem O2 bothering signals.