改良氧化銥感測元件之研究

Abstract

以RF濺鍍的方式，在白金電極上先後鍍上氧化銥薄膜與五氧化二鉭薄膜。利用五氧化二鉭薄膜只對氫離子具有單一選擇性，只能讓氫離子穿過薄膜的性質，將五氧化二鉭薄膜完全覆蓋住氧化銥薄膜，使的氧化銥薄膜只能對氫離子進行氧化還原反應，改變本身的費米能階。而由Nernst方程式可知道氧化銥的電位與溶液中的pH值成線性關係，所以可由此原理製作出五氧化二鉭-氧化銥氫離子感測電極。所製作出來的五氧化二鉭-氧化銥氫離子感測電極，改進了裸露氧化銥薄膜的氫離子感測電極，容易被其他氧化還原物質給影響的缺點。本電極具有良好的電位穩定性和重覆性的優點。 再以兩支五氧化二鉭-氧化銥氫離子感測電極為架構，製作出電位式二氧化碳感測元件。在感測實例中，兩支電極被含水及碳酸根離子的固態電解質給覆蓋住。其中一支電極用epoxy覆蓋使的不與外界接觸，視為有著固定電位的標準電極，而另一支電極是會隨著固態電解質中的氫離子濃度改變電位的感測電極，由兩支電極的電位差會因感應到二氧化碳而改變。本元件對二氧化碳具有快速感應的能力，元件的電位差對濃度也有著線性且可逆的關係。

A new H+-sensing Electrode based on sputtered Ta2O5 and IrO2 thin film. The mechanism is that only H+ can pass through Ta2O5 film. To insulate IrO2 film from intruding by other ions, IrO2 film was covered with Ta2O5 film. And the Fermi level of IrO2 film can be varied from the interaction of H+ in the electrolyte. By Nernst's equation, we can see that the potential of IrO2 film can be varied with pH value of the electrolyte. And then, we made a potentiometric CO2 sensor based on two Ta2O5-IrO2 electrodes. Both Ta2O5-IrO2 electrodes were connected and covered by water contained, bicarbonate doped poly( vinyl alcohol ). One of the electrodes was shielded with an epoxy layer. When the device was exposed to gaseous mixed of CO2, the potential difference between these two electrodes indicated the containment of CO2 in the measurand. This CO2 sensor was a rapid response device. The response to CO2 concentration was linear and reversible.