200822436 【發明說明】 本發明之主要目的在於提供一種具有碳黑/黏土載體之鉑奈米 觸媒及其製法’其可應用於燃料電池之薄膜電極。 本發明之另一目的在於提供一種均勻分散碳黑於Nafion(質子 傳導液)水溶液之方法，用以製造上述之鉑奈米觸媒。 本發明均勻分散碳黑於Nafion(質子傳導液)水溶液之方法包 括下列步驟：（a)於Nafion(質子傳導液)水溶液中，加入黏土及碳 黑’並以超音波震运混合’形成一碳黑/黏土之均句分散液。 上述之Nafion水溶液之濃度約爲2〜i〇wt%，較佳爲約5 wt%; 使用的黏土較佳爲片狀黏土；碳黑/黏土之重量比約爲 75/15〜95/15，較佳爲約85/15 ;碳黑/Nafion(質子傳導液)的重量比 約爲4/10〜4/20，較佳爲約4/15。 上述之碳黑、黏土可於Nafion(質子傳導液)水溶液中先以機械 攪拌器攪拌，再以超音波震盪混合；其中機械攪拌的時間約爲 20〜40分鐘，超音波震盪混合的時間約爲4〜7小時，溫度約爲25〜45 。。。 本發明製造鉑觸媒油墨之方法則包括下列步驟：（b)於一碳黑/ 黏土之均勻分散液中，加入氯鈾酸（chloroplatinicacid)，並以含 浸法形成鉑觸媒油墨，該碳黑/黏土之均勻分散液係以上述之方法 形成，且該碳黑/黏土係作爲觸媒載體。 上述之鉑/碳黑的重量比約爲1/3〜1/5，較佳爲約1/4。本發明 方法所製造的鉑觸媒油墨並可應用於燃料電池之薄膜電極。 本發明製造薄膜電極之方法包括下列步驟：（c)於一高分子 電解薄膜之表面塗佈鉑觸媒油墨，形成一燃料電池之薄膜電極 層，該鉑觸媒油墨係以上述之方法形成。 上述之薄膜電極層中，鉑含量約爲0.3〜0.5 mg/cm2，較佳爲約 0.4 mg/cm2 ° 200822436 【實施方法】 本發明之較佳實施例之操作步驟及結果詳述於下，其中主要 材料包括： (1) 蒙托土 ： sodium montmorillonite ( MMT )，購自 Nancor Co· 〇 (2) 碳黑：carbon black (Vulcan® XC-72)購自 Cabot、Co·。 (3) 氯鉑酸：chloroplatinic acid，購自 Seedchem。 (4) 全氟磺酸樹脂：Nafion 5購自Du pont Co·。 龜 （5)局分子電解薄膜：polymer electrode membrane，Nafior^l 12 ’ 響購自 Du pont Co·。 實施例1 1.製備觸媒載體 先將碳黑及黏土粉體以重量比85/15混合；接著加入Nafion (5%於水中），以機械攪拌器攪拌30分鐘後，再於30〜40°C下以 超音波產生器攪拌5〜6小時，完全膨潤黏土及分散碳黑顆粒，形 成『碳黑/黏土』觸媒載體。第1圖爲片狀黏土與碳黑顆粒混合的 示意圖。 • 2.製備鉑觸媒油墨 於上述混合液中加入氯鈾酸（chloroplatinic acid)作爲金屬前 驅物，以含浸法製備鉑觸媒油墨，其中鉑含量爲20 wt%，鉑/碳黑 /Nafion 的重量比爲 1/4/15，與文獻『L· Xiong，A. Manthiram， Electrochim· Acta，50 (2005) 3200』所述相同。 實施例2 重複實施例1的步驟，其中碳黑/黏土的總重量不變，但碳黑/ 黏土重量比改爲67/33，而鉑/碳黑/Nafion(質子傳導液)的比例則保 持固定。 7 200822436 比較例1 重複實施例1的步驟，但不添加黏土，亦即碳黑/黏土的重量 比爲100/0，而鉑/碳黑/Nafion(質子傳導液)的比例則保持固定。 製備薄膜電極組合物及樽細 應用例1〜2 依表1所示的配置，將實施例1、2及比較例1的觸媒油墨塗 佈於 Nafion® 112 高分子電解薄膜（polymer electrode membrane) (5 cm2)的兩面；其中觸媒油墨的鈾含量固定爲0.4 mg/cm2。塗 _ 佈過程係先完成其中一面，形成一薄膜電極組合物；於80°C、ΗΓ2[Brief Description of the Invention] The main object of the present invention is to provide a platinum nanocatalyst having a carbon black/clay carrier and a method for producing the same, which can be applied to a thin film electrode of a fuel cell. Another object of the present invention is to provide a method for uniformly dispersing carbon black in an aqueous solution of Nafion (proton conducting solution) for producing the above-described platinum nanocatalyst. The method for uniformly dispersing carbon black in an aqueous solution of Nafion (proton conducting solution) comprises the steps of: (a) adding clay and carbon black in an aqueous solution of Nafion (proton transfer) and forming a carbon by ultrasonic wave mixing Black/clay uniform dispersion. The concentration of the above aqueous Nafion solution is about 2% by weight, preferably about 5% by weight; the clay used is preferably flaky clay; the weight ratio of carbon black to clay is about 75/15 to 95/15, Preferably, it is about 85/15; the weight ratio of carbon black/Nafion (proton conducting fluid) is about 4/10 to 4/20, preferably about 4/15. The above carbon black and clay can be stirred in a Nafion aqueous solution by a mechanical stirrer and then ultrasonically mixed; wherein the mechanical stirring time is about 20 to 40 minutes, and the ultrasonic mixing time is about 4 to 7 hours, the temperature is about 25 to 45. . . The method for producing a platinum catalyst ink according to the present invention comprises the steps of: (b) adding a chloroplatinic acid to a uniform dispersion of carbon black/clay, and forming a platinum catalyst ink by impregnation, the carbon black The homogeneous dispersion of clay/clay is formed in the above manner, and the carbon black/clay is used as a catalyst carrier. The above platinum/carbon black has a weight ratio of about 1/3 to 1/5, preferably about 1/4. The platinum catalyst ink produced by the method of the present invention can be applied to a thin film electrode of a fuel cell. The method for producing a thin film electrode of the present invention comprises the steps of: (c) coating a surface of a polymer electrolyte film with a platinum catalyst ink to form a film electrode layer of a fuel cell, the platinum catalyst ink being formed by the above method. In the above thin film electrode layer, the platinum content is about 0.3 to 0.5 mg/cm 2 , preferably about 0.4 mg/cm 2 ° 200822436. [Methods of Operation] The operation steps and results of the preferred embodiment of the present invention are described in detail below. The main materials include: (1) Montmorillonite: sodium montmorillonite (MTT), purchased from Nancor Co. 〇 (2) Carbon black: carbon black (Vulcan® XC-72) was purchased from Cabot, Co. (3) Chloroplatinic acid: chloroplatinic acid, available from Seedchem. (4) Perfluorosulfonic acid resin: Nafion 5 was purchased from Du pont Co. Turtle (5) Molecular electrolytic film: polymer electrode membrane, Nafior^l 12 ’ is available from Du pont Co·. Example 1 1. Preparation of Catalyst Carrier First, carbon black and clay powder were mixed at a weight ratio of 85/15; then Nafion (5% in water) was added, stirred with a mechanical stirrer for 30 minutes, and then at 30 to 40 °. C is stirred with an ultrasonic generator for 5 to 6 hours to completely swell the clay and disperse the carbon black particles to form a "carbon black/clay" catalyst carrier. Figure 1 is a schematic representation of the mixing of flaky clay and carbon black particles. 2. Preparation of platinum catalyst ink Adding chloroplatinic acid as a metal precursor to the above mixture, preparing platinum catalyst ink by impregnation method, wherein the platinum content is 20 wt%, platinum/carbon black/Nafion The weight ratio is 1/4/15, which is the same as described in the document "L. Xiong, A. Manthiram, Electrochim Acta, 50 (2005) 3200". Example 2 The procedure of Example 1 was repeated, in which the total weight of carbon black/clay was unchanged, but the carbon black/clay weight ratio was changed to 67/33, while the ratio of platinum/carbon black/Nafion (proton conducting solution) was maintained. fixed. 7 200822436 Comparative Example 1 The procedure of Example 1 was repeated except that no clay was added, i.e., the carbon black/clay weight ratio was 100/0, and the ratio of platinum/carbon black/Nafion (proton conducting fluid) remained fixed. Preparation of Thin Film Electrode Composition and Thinning Application Examples 1 to 2 The catalyst inks of Examples 1, 2 and Comparative Example 1 were applied to Nafion® 112 polymer electrode membrane according to the arrangement shown in Table 1. Both sides of (5 cm2); the uranium content of the catalyst ink is fixed at 0.4 mg/cm2. The coating process is completed on one side to form a thin film electrode composition; at 80 ° C, ΗΓ 2
Torr下真空乾燥30分鐘後，再塗佈另一面，形成另一個薄膜電極 組合物。據此，可將高分子電解薄膜夾置於兩層觸媒油墨之間， 形成一『陽極/局分子電解薄膜/陰極』模組。 應用比較例1 重複應用例1的步驟，但高分子電極薄膜的兩面皆塗佈比較 例1所得之觸媒油墨，亦即未添加黏土，而鈾/碳黑/Nafion(質子傳 導液)的比例則不變。 表1 陰極載體 陽極載體 應用例/應用比較例 (碳黑/黏土的重量 (碳黑/黏土的重量 比) 比） 應用例1 85/15 100/0 應用例2 67/33 100/0 應用比較例1 100/0 100/0 200822436 分析及試驗 碳黑/黏十混合物之特徵分析 以場發射掃描式電子顯微鏡（FE-SEM，JEOL 6700F)對觸媒 載體作表面分析；及藉由接觸角系統FTA 200 (ACIL&FkstTen Angstroms Inc·)，以液滴法檢測碳黑/黏土表面的水接觸角（〜3如 contact angle);每一個碳黑/黏土樣品至少檢測三點。 第2圖顯示於FE-SEM下所觀察觸媒載體（碳黑/黏土之重量 比100/0、85/15及67/33 )表面形狀之結果。圖中，未添加黏土（亦 即碳黑/黏土爲100/0)的樣品產生平均粒徑〜300 nm之聚集（第 2a圖），顯示原來呈不規則球形的碳黑粉體（平均粒徑爲40〜60 nm) • 開始聚集。碳黑顆粒的聚集通常是由奈米顆粒之間的凡德瓦力引 起。聚集可能於製備過程發生，由於碳黑粉體無法完全分散於溶 劑中，因此產生肉眼可觀察到的沉澱。然而，藉由超音波攪拌， 添加黏土後的碳黑/黏土混合物可輕易地懸浮於溶劑中，如第2b 及2c圖所示。使用黏土作爲有機分散劑的效果可歸因於MMT的 .幾何結構，其明確的一級結構單元包括堆疊的片狀鋁矽酸鹽。此 片狀單元呈不規則及多粒徑分布（polydisperse)，MMT的平均大 小約爲100x100x1 mn3。由於強烈的離子電荷特性，使黏土呈親水 性並可以高濃度於溶劑及凝膠中膨潤。根據第2b及2c圖，可清 楚看岀碳黑有效地被黏土分散，其平均粒徑約爲40〜60 nm。 第3圖爲液滴試驗結果，圖中添加0、15及33 wt%黏土之碳 _ 黑/黏土表面的水接觸角分別爲130.0°、110.4°及90·6°。顯然地， 增加黏土比例可減少水接觸角；亦即，添加黏土將可改善觸媒載 體的潤濕性。 燃料電池之極化試驗 薄膜電極組合物的極化曲線係於燃料電池系統（BEAM ASSOCIATE CO·，LTD)中檢測。反應物（氫及氧）的流率爲100 seem，並保持在5(TC的水蒸氣飽和溫度。整個試驗過程中，單一 電池的溫度保持在60°C。 第4圖係以電壓-電流曲線圖（V-I plot)表示極化試驗的結 果。三種樣品的開路電壓（open circuit voltage)約爲0·89 V ;在 9 200822436 PEMFC的標準狀態下，燃料電池於電化學反應中的可逆電位 (reversible potential)爲1.2V 〇然而，由於不可逆損失的緣故， 三種樣品的實際電壓皆應低於理論値。此外，碳黑/黏土 = 85/15 的薄膜電極組合物具有最寬的歐姆極化（ohmic polarization)範圍 (5〇〜l，l5〇mA/cm2);較碳黑/黏土 =1〇〇/〇的薄膜電極組合物稍 大（50〜810 mA/cm2) of the碳黑/黏土=67/33 case薄膜電極組合 物。這些數據證明添加黏土可明顯改善歐姆極化。此外，電流密 度較高時，極化曲線開始受到質量傳送限制的影響，顯示有必要 增加陰極的潤濕性及親水性。 第5圖則進一步以功率密度對電流作圖（P-I plot);其中， 碳黑/黏土 = 85/15的薄膜電極組合物在電流密度爲670 mA/cm2 • 時，具有較佳的功率輸出（230 mW/cm2)，相較於碳黑/黏土 = 100/0 的薄膜電極組合物（200 mW/cm2，570 mA/cm2)及碳黑/黏土 = 67/33的薄膜電極組合物（200 mW/cm2，470 mA/cm2)，顯然較 、觸媒油墨之微結構及晶相分析 微結構及晶相分析係以Zeiss 902 A TEM作選區繞射（selected area diffraction，SAD)圖形觀察，並與 JCPDS Data File 的標準化 合物比對。 第6圖顯τκ鉑/碳黑/黏土重量比爲20/85/15的觸媒油墨的明視 • 野（bright field)影像；圖中鉑及碳黑顆粒的微結構以不同階層顯 示。根據文獻『D.B· Williams，C.B· Carter，Transmission Electron Microscopy，Plenum，New York，1996、ρρ· 351-354』所述，對於厚 度均勻的樣品，分散在高Z區域（high-Z region，亦即高質量區域） 的電子應較低Z區域（low-Z region)爲多。因此，鉑或高Z區 域的對比情形較明顯，含碳區域則相反。第6圖亦顯示，藉由含 浸法，可使鉑顆粒（平均粒徑爲5 nm)均勻分佈於觸媒載體。第 7圖爲其SAD圖形，其（111)方向的面距（d spacing)經檢測爲 2·265 A 〇 由上述試驗分析結果證明：藉由超音波震盪，可將碳黑及片 狀黏土均勻分散於5 wt%的Naficm(質子傳導液)溶液及水中，不需 額外的有機分散劑。由水接觸角試驗證明：添加黏土可有效增加 200822436 觸媒載體的親水性。此外，由極化及功率密度試驗結果，碳黑/黏 土 = 85/15的薄膜電極組合物較碳黑/黏土=1〇〇/0及67/33者爲佳。 TEM影像可看到均勻分布於觸媒載體上的鉑顆粒，其平均粒徑爲 5 nm ° 【圖式簡單說明】 第1圖爲片狀黏土與碳黑顆粒混合的示意圖 第2圖顯示於FE-SEM下所觀察不同碳黑/黏土重量比之觸媒載體 表面形狀之結果。 第3圖爲不同碳黑/黏土重量比之觸媒油墨液滴試驗結果。 φ 第4圖爲電池電壓對電流之曲線圖（V-I plot)。 第5圖爲薄膜電極組合物功率密度對電流之圖（p_Ipl〇t：)。 第6圖顯示鉑/碳黑/黏土重量比爲20/85/15的觸媒油墨的明視野影 像。 第7圖顯示舶/碳黑/黏土重量比爲2〇/85/15的觸媒油墨的SAD圖 形。After drying under vacuum for 30 minutes under Torr, the other side was coated to form another thin film electrode composition. Accordingly, the polymer electrolyte film can be sandwiched between two layers of catalyst ink to form an "anode/intermolecular electrolytic film/cathode" module. Application Comparative Example 1 The procedure of Application Example 1 was repeated, but the catalyst ink obtained in Comparative Example 1 was coated on both sides of the polymer electrode film, that is, the ratio of uranium/carbon black/Nafion (proton conducting solution) was not added. It does not change. Table 1 Cathode Carrier Anode Carrier Application/Application Comparison Example (Carbon Black/Clay Weight (Carbon Black/Clay Weight Ratio)) Application Example 1 85/15 100/0 Application Example 2 67/33 100/0 Application Comparison Example 1 100/0 100/0 200822436 Analysis and testing of carbon black/viscosity mixture characteristics analysis by field emission scanning electron microscopy (FE-SEM, JEOL 6700F) for surface analysis of catalyst carriers; and by contact angle system FTA 200 (ACIL & FkstTen Angstroms Inc.), the water contact angle of the carbon black/clay surface (~3 such as contact angle) is detected by the drop method; at least three points are detected for each carbon black/clay sample. Fig. 2 shows the results of the surface shape of the catalyst carrier (carbon black/clay weight ratios 100/0, 85/15 and 67/33) observed under FE-SEM. In the figure, samples without added clay (ie, carbon black/clay 100/0) produced aggregates with an average particle size of ~300 nm (Fig. 2a), showing carbon black powders (average particle size) that were originally spherical in shape. 40 to 60 nm) • Start to gather. The aggregation of carbon black particles is usually caused by van der Waals forces between the nanoparticles. Aggregation may occur during the preparation process, since the carbon black powder cannot be completely dispersed in the solvent, so that a precipitate which is observable to the naked eye is produced. However, by ultrasonic agitation, the carbon black/clay mixture after the addition of the clay can be easily suspended in the solvent as shown in Figures 2b and 2c. The effect of using clay as an organic dispersant can be attributed to the geometry of the MMT, whose well-defined primary structural unit comprises stacked flaky aluminosilicates. The sheet unit has an irregular and multi-disperse distribution, and the average size of the MMT is about 100 x 100 x 1 mn3. Due to the strong ionic charge characteristics, the clay is hydrophilic and can swell at high concentrations in solvents and gels. According to Figures 2b and 2c, it can be clearly seen that the carbon black is effectively dispersed by the clay and has an average particle diameter of about 40 to 60 nm. Figure 3 shows the results of the drop test. Adding 0, 15 and 33 wt% clay carbon _ black/clay surface water contact angles are 130.0°, 110.4° and 90·6°, respectively. Obviously, increasing the proportion of clay reduces the water contact angle; that is, adding clay will improve the wettability of the catalyst carrier. Polarization test of fuel cell The polarization curve of the thin film electrode composition was detected in a fuel cell system (BEAM ASSOCIATE CO·, LTD). The flow rate of the reactants (hydrogen and oxygen) was 100 seem and was maintained at 5 (the water vapor saturation temperature of TC. During the entire test, the temperature of the single cell was maintained at 60 ° C. Figure 4 is a voltage-current curve Figure VI shows the results of the polarization test. The open circuit voltage of the three samples is about 0·89 V. In the standard state of 9 200822436 PEMFC, the reversible potential of the fuel cell in the electrochemical reaction (reversible) The potential) is 1.2V. However, due to the irreversible loss, the actual voltage of the three samples should be lower than the theoretical 値. In addition, the carbon black/clay = 85/15 thin film electrode composition has the widest ohmic polarization (ohmic) Polarization range (5〇~l, l5〇mA/cm2); slightly larger than the carbon black/clay=1〇〇/〇 film electrode composition (50~810 mA/cm2) of the carbon black/clay=67 /33 case film electrode composition. These data demonstrate that the addition of clay can significantly improve the ohmic polarization. In addition, when the current density is high, the polarization curve begins to be affected by the mass transfer restriction, indicating that it is necessary to increase the wettability and hydrophilicity of the cathode. Sex 5 Further plotting the power density versus current (PI plot); wherein the carbon black/clay = 85/15 membrane electrode composition has a better power output (230 mW/cm2 at a current density of 670 mA/cm2 • • ), compared to a film electrode composition of carbon black/clay = 100/0 (200 mW/cm2, 570 mA/cm2) and a carbon black/clay = 67/33 film electrode composition (200 mW/cm2, 470) mA/cm2), apparently, the microstructure of the catalyst ink and the crystal phase analysis microstructure and crystal phase analysis were observed by the Zeiss 902 A TEM as a selected area diffraction (SAD) pattern, and with the JCPDS Data File Standard compound alignment. Figure 6 shows the bright field image of the τκ platinum/carbon black/clay catalyst ink with a weight ratio of 20/85/15; the microstructure of the platinum and carbon black particles in the figure Displayed by different classes. According to the literature "DB· Williams, CB· Carter, Transmission Electron Microscopy, Plenum, New York, 1996, ρρ·351-354", for samples of uniform thickness, dispersed in the high Z region (high-Z) The region, ie the high quality region, should have a lower Z region (low-Z re Gion) is more. Therefore, the comparison of platinum or high Z regions is more obvious, and the carbon-containing regions are opposite. Figure 6 also shows that platinum particles (average particle size of 5 nm) can be uniformly distributed on the catalyst carrier by the impregnation method. Figure 7 is its SAD pattern, and its d-distance in the (111) direction is detected as 2·265 A. The results of the above test analysis prove that the carbon black and the flaky clay can be uniform by ultrasonic vibration. Dispersed in 5 wt% Naficm solution and water without additional organic dispersant. The water contact angle test proves that adding clay can effectively increase the hydrophilicity of the 200822436 catalyst carrier. In addition, as a result of the polarization and power density tests, the film electrode composition of carbon black/soil = 85/15 is better than carbon black/clay = 1 〇〇/0 and 67/33. The TEM image shows platinum particles uniformly distributed on the catalyst carrier, and the average particle size is 5 nm ° [Simplified illustration] Figure 1 is a schematic diagram of the mixture of sheet clay and carbon black particles. Figure 2 shows the FE. - The results of the surface shape of the catalyst carrier for different carbon black/clay weight ratios observed under SEM. Figure 3 shows the test results of the catalyst ink droplets for different carbon black/clay weight ratios. φ Figure 4 is a plot of battery voltage versus current (V-I plot). Figure 5 is a plot of power density versus current for a thin film electrode composition (p_Ipl〇t:). Figure 6 shows a bright field image of a catalyst ink having a platinum/carbon black/clay weight ratio of 20/85/15. Figure 7 shows the SAD pattern of the catalyst ink with a carbon/clay weight ratio of 2〇/85/15.
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