| 摘要: | 本研究主要探討利用醇類還原法製作連續且規則結構之多孔碳(OPC,
Ordered Porous Carbon) 作為陰極觸媒載體及摻雜第二金屬與鉑(Pt,
Platinum) 形成合金觸媒應用於質子交換膜燃料電池(Proton Exchange Membrane Fuel Cell, PEMFC)，進而提升觸媒利用率及提升氧化還原活性(ORR, Oxygen Reduction Reaction)，此外，利用固相反應法(Solid State Reaction, SSR)製作傳統及合金陽極應用在質子傳輸型固態氧化物燃料電池(Proton Conducting Solid Oxide Fuel Cell, P-SOFC)，進而提升材料之機械性質、催化活性、導電性、抗碳沉積能力及氧化還原穩定性。在PEMFC 研究方面，提升觸媒利用率與效能是極為重要課題，目前PEMFC 之觸媒載體大多使用碳黑為主，但由於碳黑會使觸媒形成孤島效應，導致觸媒利用率降低，因此使用OPC 作為載體，進而改善此一缺點，並且選用錫(Sn, Stannum)作為PtSn/C 合金觸媒，藉以降低Pt 使用量，達成降低PEMFC 之生產成本，並且在酸性環境下，能提升電池之ORR 活性。實驗先以Pt/C 為基材，比較Sn 摻雜，隨後再將載體換成OPC，進行電化學與長時間穩定性測試，目標是以少許Sn 及OPC 取代Pt 及碳黑，達到比傳統以純Pt 金屬為主之陰極具有較佳之電化學性能及長時間穩定性。在SOFC 研究方面，先以NiO-BCY 為基材，比較Zr 摻雜，進行氧化還原前後之陽極材料，量測則分為晶相鑑定、微觀結構、觸媒活性及機械性質分析；隨後以合金陽極量測則分為成份比例、晶相鑑定、微觀結構、機械性質及電性分析，藉由調整鎳鈷合金(Nickel Cobolt Alloy, NiCo Alloy)的煆燒溫度、煆燒時間及改變NiCo Alloy 比例，目標是以少許鈷元素(Cobalt,Co)與鎳元素(Nickel, Ni)置換之陽極達到比純Ni 金屬為主之陽極具有較佳
之電性、抗碳沉積能力及氧化還原循環穩定性。此外，藉由調整鎳銅合金(Nickel Copper Alloy, NiCu Alloy)的煆燒溫度、煆燒時間及改變NiCu Alloy比例，量測合金陽極之晶相鑑定、微觀結構及電性分析。研究結果顯示，利用醇類還原法製備PtSn/OPC 於PEMFC，其觸媒分散性良好，粒徑為2.7 nm，並且Sn 合金及OPC 載體不僅可以修飾Pt 及Sn之表面電化學組態，而且會影響Pt 之d 帶空缺。此外，由XPS 及XANES結果顯示，經過長時間穩定性測試前後，Sn 合金及OPC 可以抑制Pt 氧化，
進而提升ORR 活性。利用SSR 製備Ni-BCZY 陽極材料，經過多次氧化還原後，會提升觸媒活性及改善機械性質。此外，藉由調整NiCo 合金粉末煆燒溫度及煆燒時間會改變NiCo 合金晶粒大小及導電度。當Ni0.9Co0.1合金之煆燒溫度為1000 ºC及3 小時，操作溫度為600 ºC 時，Ni0.9Co0.1-BCZY 陽極之導電度為2623.5 S/cm 。當煆燒溫度及煆燒時間分別固定為1000 ºC 及1 小時，Ni0.9Co0.1-BCZY 陽極有最佳的電子導性為2669.8 S/cm 及熱膨脹係數為15.7× 10-6 K-1，相較於Ni-BCZY 陽極來的好。隨後改變NiCo 成份比例，當Ni :Co 之莫爾比為9 : 1 時，Ni0.9Co0.1-BCZY 陽極具有相當優異之導電度，其導
電度比Ni-BCZY 陽極(2354 S/cm)高，當Ni : Co 之莫爾比為7 : 3 時，其熱膨脹係數為13.6 × 10-6 K-1、有最佳的抗碳沉積能力及經過氧化還原循環後有最佳機械強度。另一方面，藉由調整NiCu 合金粉末煆燒溫度及煆燒間會改變NiCu 合金晶粒大小及導電度。當Ni0.9Cu0.1 合金之煆燒溫度為700 ºC及3 小時，操作溫度為600 ºC 時，Ni0.9Cu0.1-BCZY 陽極之導電度為2002.1 S/cm。當煆燒溫度及煆燒時間分別固定為700 ºC 及1 小時，Ni0.9Cu0.1-BCZY陽極有最佳的電子導性為2204.7 S/cm。隨後改變NiCu 成份比例，當Ni : Cu之莫爾比為9 : 1 時，Ni0.9Cu0.1-BCZY 陽極具有相當優異之導電度。;In this research, Alcohol reduction method is used to prepare continuous and ordered structure of porous carbon as catalyst support for proton exchange membrane fuel cell (PEMFC) to enhance the catalyst utilization and improve electron transfer. Pt-M alloy catalysts have higher oxidation reduction reaction(ORR) activity than pure Pt catalysts. In addition, solid state reaction (SSR)synthesis process is chosen to develop a traditional anode and an alloy catalyst as an anode in proton conducting solid oxide fuel cell (P-SOFC). The improvement of mechanical properties, catalytic activity, conductivity, carbon-resistant ability and redox stability. In the aspect of PEMFC, increasing catalyst utilization and activity are very important. Currently, carbon black is widely used as the catalyst support.
Although using carbon black to support catalyst can improve catalyst dispersion and catalyst activity, it results in loss of catalytic use due to occasional island
formation. Therefore, ordered porous carbon (OPC) is used as the catalyst support for fuel cell application due to its large surface area and continuous structure. The noble metal, Sn, is a promising candidate to replace Pt. Addition of Sn into Pt/C not only reduces cost by lowering Pt loading, but also increase ORR activity in acidic environment of fuel cell. Three catalysts are discussed during electrochemical performance and long term stability. The aim is to use little Sn and OPC to replace Pt and carbon black. The best electrochemical
performance and long term stability of catalysts are obtained compared with pure Pt catalysts.
In the aspect of SOFC, NiO-BCY anode as the based compared with Zr doped NiO-BCY. Anode is measured to phase identification, microstructure, catalytic activity and mechanical properties. After that, anode alloy is characterized to identify the ratio of components, phase identification, microstructure, mechanical properties and electrical conductivity. The aim of this research is to synthesize a higher electrical conducting anode catalyst for P-SOFC, when compared to the traditional NiO anode. Incorporation of Co(cobalt) in Ni (nickel) can enhance the electrical properties of anode in P-SOFC.
Several variations in the ratio of alloy (Ni : Co) and calcining parameters such astemperature, time would enhance the electrical conductivity, carbon deposition
resistance and the redox cycle stability of the catalyst. This is better than traditional NiO catalyst. In addition, Several variations in the ratio of alloy (Ni :
Cu) and calcining parameters such as temperature, time would improve the electrical conductivity The results show that PtSn alloy nanoparticles with a size of 2.7 nm are deposited on OPC by using alcohol reduction method. The synergistic effect of Sn alloying and OPC support can not only modify the surface chemical states of
Pt and Sn but also affect the d-band vacancy of Pt. The X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge spectroscopy (XANES)
reveal that the oxidation of Pt is suppressed in PtSn/OPC, thus promoting the ORR performance before and after accelerated durability test. SSR is used to prepare Ni-BCZY and the catalytic activity, mechanical properties are improved during redox cycling. In addition, variation of calcined temperature and calcined time can change the particle size and electrical conductivity. Initially, we investigated the best appropriate calcination
temperature and duration, and then the ratio of Ni : Co is varied. Experimental
results show that the NiCo alloy synthesized with a molar ratio of 9 : 1 (Ni : Co) calcined at 1000 ºC for 1 hour is exhibiting an electrical conductivity of 2669.8
S/cm at an operating temperature of 600 ºC with a TEC of 15.7 × 10-6 K-1. The best carbon deposition resistance, stability in redox cycle and TEC of 13.6 × 10-6
K-1 is observed for the Ni : Co molar ratio of 7 : 3. The NiCo anode hasrelatively good electrical conductivity than Ni anode (2354 S/cm). This work can help to replace the traditional NiO anode in P-SOFC. On the other hand, results show that the NiCu alloy synthesized with a molar ratio of 9 : 1 (Ni : Cu) calcined at 700 ºC for 1 hour is exhibiting an electrical conductivity of 2204.7 S/cm at an operating temperature of 600 ºC. |
