氧化鎢及氧化銥薄膜及其二極體之電化學研究

Abstract

濺鍍之氧化鎢(WO3)和氧化銥薄膜(SIROF's)的電色現 像,由循環伏安法來作分析.實驗顯示氧化鎢其化還原電位在酸性溶液中偏 向正電位,從循環伏安的圖形,氧化鎢薄膜有一較小的電荷轉移速率(~10 ^-2 s^-1(mol/cm^3)^-2)和氫離子擴散速率(10^-9 cm^2/s),而氧化銥的 循環伏安實驗,其電流與掃描速率成正比(< 500 mV/s),顯示氧化銥薄膜具 電容性,循環伏安電流為其感應電流(nonfaradic).從電位對pH 的依賴性 量測顯示,氧化銥電位對pH的改變梯度為-60.2 mV/pH,氧化鎢在酸性溶液 中電位對pH 的改變梯度為 -52.7 mV/pH. 我們利用氧化鎢為陰極電色,氧 化銥為陽極電色,以及其電性(電位,電阻)對溶液pH 的反應,製成 WO3/ IrO2 電化學二極體(其"onset"電位會隨著pH 而改變,-59 mV/pH),來感測 二氧化碳. The electrochromism of sputtered tungsten trioxide(WO3)film and iridium oxide(IrO2) film were characterized by cyclic voltammetry.Cyclic voltammograms show WO3 has mmore positive potential in acid solutions;small charge transfer rate constant(~10^-2 s^-1(mol/cm^3)^-2) andhydrogen diffusion coefficient(~10^-9cm^2/s). IrO2 thin film electrodescyclic voltammetric current that is propontial to the scan rate in therange 1-500 mV/s. The current is capacitive and nonfaradic. Frommeasurements of the open-circuit potential, the sensitivity slope of IrO2in acid and base solutions is -60.2 mV/ pH and that of WO3 in acid solutionsis -52.7 mV/pH. WO3(a cathodic electrochromic material) and IrO2(a anodicelectrochromic mmaterial) connected together forms a pH sensitivity WO3/IrO2electrochemical diode(it's onset voltage is changed by different pH) thatcan be used to sense CO2.