臺灣博碩士論文加值系統

本研究是以含浸還原法在Nation R 117上析鍍白金觸媒層，製備不同型式之感測元件，探討不同元件對一氧化碳之感測行為。
不同析鍍條件所製備之Pt/Nafion R 電極，得到不同之白含析鍍量，以0.02M氯化四氨亞鉑水溶液，於40℃含浸2小時，再以0.2M硼氫化鈉水溶液，於40℃,pH11還原30分鐘，可得最大的自含析鍍量1.40mg/cm2，以SEM觀察表面結構，自金析鍍層呈一塊狀結構。
以單面白金析鍍層(Pt/Nafion R)進行一氧化碳電化學分析，得感應極限電流之電位窗範圍在 0.6∼0.7 V vs.Ag/AgCl間，以0.65V vs. Ag/AgCl感測一氧化碳，得感測電流與一氧化碳濃度成良好的線性關係，由還原劑溶液pH10∼13所製備之Pt/Nafion。電極，應答時間皆約30秒以pH11製得的電極對一氧化碳感測靈敏度(0.36μA/ppm CO)最高。
以兩極式PtA/Nafion R /PtB所得感測極限電流之電位窗範圍在0.1∼0.2V vs. PtB間，且背景電流小於10μA以0.15V vs. PtB感測一氧化碳，得感測電流與一氧化碳濃度成良好的線性關係，感測靈敏度為0.32μA/ppm CO，但應答時間約需400秒。
以三極式PtA-PtB/Nafion R /Ptc進行一氧化碳電化學分析，工作電極(PtA)與對電極(PtB)位於Nafion R 同一側，而另一側為參考電極(Ptc)，以此感測元件在不含輔助電解質情況下﹁探討不同製備條件之感測行為，由極化曲線得感測極限電流之電位窗範圍在-0.20∼-0.10V vs. Ptc間。以-0.15V vs. Ptc進行靈敏度測試，得到製備條件以濃度在0.02M以上之氯化四氨亞鉑水溶液，於40℃含浸2小時以上，再以濃度為0.2M以上之硼氫化鈉水溶液，於40℃，pH11還原30分鐘以上，可得最高之靈敏度(0.33 μA/ppm CO)。以此製備條件，進行無水狀態測試，在相對濕度為96.4%，91.4%，84.0%，75.2%及69.3%環境下感測電流與一氧碳濃度間成一良好之線性關係，靈敏度分別為0.33，0.30，0.26,0.20，及0.17μA/ppm CO，隨著相對濕度降低而減小，而應答時間皆約30秒。在含25%氧氣的氮氣中感測一氧化碳，由氧氣的極化曲線中得知，在施加電位比-0.15V vs. Ptc更負時，氧氣迅速進行還原反應。為降低氧氣之影響，以-0.1V vs. Ptc感測一氧化碳。在相對濕度為87.5%時，感測電流與一氧化碳濃度間仍呈一良好的線性關係，得靈敏度為0.175μA/ppm CO，相對於無氧狀態下，減少了0.1μA/ppm CO。

Pt was loaded on Nafion R for different types sensing cells with impregnation-reduction method. The sensing behaviors on CO with these cells were then studied.
Pt loading depended upon the electrode preparing conditions. The electrode for the maximum Pt loading (1.40 mg/cm2) was obtained with impregnation in 0.02 M Pt(NHs)4Cl2 at 40℃ for 2 hrs, then reduction in 0.2 M NaBH4, pH11 at 40℃ for 30 min. The surface of the deposite was observed in the form of black with SEM.
The applied voltage for limiting current of CO oxidation on the Pt/Nafion R electrode was in the range of 0.6~0.7 V vs. Ag/AgCl. The sensing current of CO on the Pt/Nafion R electrode was proportional to CO concentration at 0.65 V vs. Ag/AgCl. The highest sensitivities of CO for Pt/Nafion R electrodes prepared with reducing solution of pH 10~13 is 0.36 μA/ppm CO at pH 11. The response time these pH was about 30 sec.
The applied voltage for limiting current of CO oxidation on the PtA/Nafion R /Pta cell was in the range of 0.1~0.2 V vs. PtB, with background current smaller than 10 U.A. The sensing current of CO on the PtA/Nafion R /Pta cell was proportional to CO concentration at 0.15 V vs. Pte. The sensitivity and respose time were 0.32πA/ppm CO and about 400 sec.
The applied voltage for limiting current of CO oxidation on the PtA-PtB/Nafion R /Ptc cell was in the range of -0.20~-0.10 V vs. Ptc. PtA and Pts were separated and situated on the same side of Nation R and used as the working and counter electrode respectively. On the other side was the reference electrode. The sensing current of CO on this cell was proportional to CO concentration at 0.15 V vs. Ptc. The preparation condition for PtA-PtB/Nafion R /Ptc cell with the maximum sensitivity of CO (0.33 μA/ppm CO) was impregnation in 0.02 M Pt(NH3)4Cl2 at 40℃ for 2 hrs, and reduction with 0.2 M NaBH4, pH11 at 40℃ for 30 min. The sensitivities of CO of PtA-PtB/Nafion R /Ptc cell without eletrolyte outside of Nation R were 0.33, 0.30, 0.26, 0.20, and 0.17μA/ppm CO for relative humidity 96.4%, 91.4%, 84.0%, 75.2%, and 69.3%, respectively. The response time was about 30 sec. When the applied voltage was more negative than -0.15V vs. Ptc, O2 was reduced easily with 20% 02 in N2. The sensitivities of CO for PtA-PtB/Nafion R /Ptc cell in synthesis air with RH 87.5% is 0.175 μA/ppm CO at -O.1 V vs. Ptc. This sensitivity was smaller than that without O2 influence.