| 摘要: | 近年來，文獻中廣泛討論利用常溫離子液體 (room temperature ionic liquid, RTIL）替代傳統酸性電解液在安培型氣體感測器表現之電化學性能，因其具有低蒸氣壓，寬廣的電化學視窗，電化學及熱穩定性，以及高的離子導電性。為了符合新型安培臭氧(ozone, O3) 氣體感測器用於無線感測器網絡（WSN）的下列需求，如低偵測極限(ppb等級)、高選擇性、穩定的電流反應和良好的穩定性，因此本研究以甲酸還原法製備碳支撐鉑(Pt)，及鉑基二元和三元觸媒，噴塗在聚四氟乙烯（Polytetrafluoroethene, PTFE）薄膜上作為工作電極，並使用多種RTIL和H2SO4作為電解液。本實驗製備之O3感測器透過恆電位儀量測的電化學4S 測試包括：靈敏度、穩定性、選擇性、響應和恢復時間，而製備之觸媒結構、表面組成、化學組成、形貌和電化學性能分析可藉由X光繞射儀(X-ray diffraction, XRD)、光電子能譜儀(X-ray photoelectron spectroscopy, XPS)、能量散射光譜儀(energy dispersive spectrometer, EDS)、高解析度穿透式電子顯微鏡(high resolution transmission electron microscope, HRTEM)等儀器鑑定。
本研究分為四個部分，在第一部分中，製備碳支撐之鉑、鉑金、鉑銀、鉑錫和鉑金銀的奈米棒（nanorods, NRs）。XRD分析中，鉑金和鉑金銀具有不均勻的結構，而EDS和XPS結果顯示鉑銀和鉑金銀的表面富含銀。
第二部分分別利用硫酸、BMP、HMI、P6,6,6,14、BF4和BMI電解液在鉑金電極上之安培O3感測能力。硫酸在所有電解液中呈現最高的靈敏度，但BMP對於靈敏度的回歸線性、選擇性、穩定性、響應和回復時間均優於H2SO4。
第三部分，探討利用BMP電解液分別於鉑、鉑金、鉑銀、鉑錫電極之O3感測能力。鉑銀的響應和恢復時間在所有觸媒中是最迅速的，比鉑金的時間快上許多。然而，鉑金是該部分中唯一符合空氣質量指數（AQI）檢測範圍的觸媒。綜合所述，鉑金銀作為工作電極是一種很有潛力的觸媒，不僅可以提供更大的檢測範圍，而且可以提高靈敏度和反應速度。
在第四部分中，比較鉑金銀-211和鉑金銀-611電極在BMP中之O3感測能力。鉑金銀-611的靈敏度、響應和恢復時間均優於鉑金銀-211電極，其為本研究中靈敏度最高的觸媒(10.5 nA/ppm)，鉑金銀-611安培感測器的對於O3也有優異的選擇性，而對混合氣體（100 ppb NO、100 ppb SO2、10 ppm CO和N2平衡氣體）沒有反應，且電流反應在50到150 ppb的濃度區間與光化學式感測器有很高的一致性，顯示此三元材料搭配BMP電解液為具有潛力之電化學O3感測器。
;The electrochemical performance of amperometric gas sensors using room temperature ionic liquid (RTILs) electrolytes to substitute conventional acid liquid has been widely discussed in recent year due to their low vapor pressure, wide electrochemical window, electrochemical and thermal stability and high ionic conductivity. In order to meet the requirement of newly developed amperometric O3 gas sensors for wireless sensor network (WSN), such as low detection limit (ppb level), high selectivity, stable current response and good stability, in this study, carbon-supported Pt, Pt-based binary and ternary catalysts are prepared by formic acid reduction method (FAM) then sprayed on polytetrafluoroethylene (PTFE) membrane as working electrode, and various RTILs and H2SO4 are used as electrolytes. The electrochemical characterizations (4S tests, including: sensitivity, stability, selectivity, speed (response and recovery time)) of O3 sensors are measured by potentiostat, and the lattice structures, surface compositions, chemical compositions, morphologies and electrochemical properties of prepared catalysts are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectrometer (EDS) and high resolution transmission electron microscopy (HRTEM), respectively.
This study is divided into four parts. In the first part, the carbon-supported Pt and Pt-based nanorods (NRs) including PtAu, PtAg, PtSn, and PtAuAg have been prepared. XRD analysis has shown that PtAu, and PtAuAg have an inhomogeneous structure and the EDS and XPS results indicate that the surface of PtAg and PtAuAg is Ag-rich.
In the second part, amperometric O3 sensing of H2SO4, BMP, HMI, P6,6,6,14, BF4 and BMI electrolytes on PtAu electrode is studied. H2SO4 presents the highest sensitivity among all electrolytes, however the performance of linearity, selectivity, stability, response and recovery time of BMP is superior to those of H2SO4.
In the third part, amperometric O3 sensing of Pt, PtAu, PtAg and PtSn electrodes in BMP electrolyte is studied. The response and recovery time of PtAg are the best among the catalysts, much faster than those of PtAg. However, PtAu is the only catalyst in the section that meets the detection range of air quality index (AQI). To sum up, PtAuAg is a promising catalyst to present not only wide detection range but also high sensitivity and speed for O3 sensing.
In the fourth part, amperometric O3 sensing of PtAuAg-211 and PtAuAg-611 electrodes in BMP electrolyte are compared. The sensitivity, response and recovery time of PtAuAg-611 are better than those of PtAuAg-211 electrode with the highest sensitivity of 10.5 nA/ppm among all catalysts. Moreover, the selectivity of PtAuAg-611 amperometric O3 sensor shows no response to gas mixture (100 ppb NO, 100 ppb SO2, 10 ppm CO and N2 balanced gas) and the current response in the range of 50 to 150 ppb is highly consistent with the ultraviolet (UV) photometric analyzer, suggesting that PtAuAg-211 electrode with BMP electrolyte is a promising electrochemical O3 sensor. |
