研究計畫摘要
Project Abstract
The main goal of the project is to develop next generation gas diffusion electrodes (GDEs) for Anion Exchange Membrane Fuel Cells (AEMFCs), which demonstrate improved efficiency and durability, whilst using sustainable and affordable materials. It has been recognized that fuel cells should play a major role in the transformation to a future low carbon economy, being an important pillar of the Strategic Energy Technologies Plan (SET) Plan2-3, adopted by the European Council. The Need for fuel cell technologies has been identified as being essential in order to meet Europe’s and Asia's energy, environmental and economic challenges in transport and energy applications. Today's state-of-the-art fuel cells, in particular proton exchange membrane fuel cells (PEMFCs), are now at a high TRL status (TRL=6-8). However, PEMFCs are still in need of high loadings of precious metals, especially Platinum group metals (PGMs), the scarcity of which leads them to be considered critical raw materials for EU and the world.
In common with the PEMFC, the AEMFC is an all-solid electrochemical device able to generate high power outputs. The difference being that AEMFCs are built around an alkaline, rather than acidic, electrolyte membrane. The higher pH environment gives some advantages over the acid PEMFC, in particular: i) the potential use of Non-PGM catalysts for the oxygen reduction reaction (ORR), ii) the potential use of lower cost materials for stack components and iii) a wider choice of fuels, including H2, ammonia, urea, and other nitrogen based fuels. The slow progress of this technology to date has been due the poor stability of anion exchange membranes. Significant advances have recently been made regarding membrane stability though, and consequently it is now recognized that the other AEMFC components also need to be improved. In order for the AEMFCs to become a commercially available energy converting devices, the following challenges need to be addressed: i) the anion conductive phase within the electrodes, also called ionomer, still suffers degradation, specially affecting the cathode side of the AEMFC and ii) the efficiency of the hydrogen oxidation reaction (HOR) at the anode falls well behind PEMFCs due to the slow kinetics of oxidation reaction in alkaline medium. Based on these needs, NEXTGAME has the following sub objectives:
SO1: To formulate stable alkaline ionomers to be used as the anionic conductive phase in AEMFC electrodes with the aim of increasing electrode durability.
SO2: To develop active Non-Pt/non-PGM anode catalysts for the hydrogen oxidation reaction (HOR) with the aim at reducing the costs compared to state-of-the-art Pt-based catalysts.
SO3: To develop Non-PGM Metal oxide-based cathode catalyst for the oxygen reduction reaction (ORR) in alkaline media with the aimed at increasing cathode lifetime during operation.
SO4: To fabricate gas diffusion layers (GDLs), specifically design to be used as substrates for AEMFCs gas diffusion electrodes (GDEs). The aim is to improved performance and increase durability of the electrodes.
SO5: To overcome the challenges involving the integration of these materials into fully functional GDEs for efficient and durable AEMFC operation.
本計畫主要目標是發展次世代氣體擴散電極適用於陰離子交換膜燃料電池(AEMFC)，能展現出效率改善與耐久性，得以使用永續與可負擔的材料。備受認同的是燃料電池在未來低碳經濟的重要角色，同時也是歐洲議會規劃策略能源計畫計畫2-3的重要分支。燃料電池技術已被認定重要性，以於符合歐亞能源、環境與經濟挑戰，發展於運輸與能源應用端。就當代燃料電池技術而言，質子交換膜燃料電池(PEMFC)歸類於技術等級(TRL=6-8)，但其高使用量貴重金屬作觸媒，特別是白金用量，以令歐盟與世界感到此關鍵原料之缺乏問題。
原理上PEMFC與AEMFC都是屬於固態電化學裝置作高電力產出，差異點在於AEMFC使用鹼性電解膜，PEMFC是酸性。鹼性環境有以下潛在優點: i)可使用非貴金屬作氧化還原，ii)可使用較低成本材料作電堆組裝，iii)燃料多元化，氫氣、氨、脲、和其他有氮燃料。過去緩慢進展，導因於陰離子交換膜穩定性差，近來重要提升膜之穩定性，AEMFC相關元件得以獲得改善。基於此論，AEMFC有機會成為商業化的能源轉化裝置，然而有待以下幾點作克服: i)陰離子導電分子於電極內，仍存在降解，特別是影響陰極端，ii)於陽極端的氫氣氧化落後於PEMFC，主因於在鹼性介質有較慢的氧化動力。基於此需要，提出本計畫(NEXTGAME)以下分項計畫執行。
分項一: 配方出穩定的鹼性離子高分子，作為陰離子導電相於AEMFC電極內，提升電極耐久性。分項二: 發展活化的非貴金屬陽極觸媒作氫氣的氧化反應，降低於現有使用白金之成本。分項三: 發展非貴金屬氧化陰極觸媒，於氧氣還原反應中增加陰極使用壽命。分項四: 製作氣體擴散層專用於AEMFC，得以改善效能與提升耐久性。分項五: 克服各項整合材料之挑戰，以進入全功能性運轉有效率與耐久的AEMFC。