Improvement of PEMFC Performance by Coating Hygroscopic ZnO on the Anodic Catalyst Layer

• Main Authors: Tsai-Wei Chiu, 邱采薇
• Other Authors: 薛富盛
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/61392048851027272246

碩士 === 國立中興大學 === 材料科學與工程學系所 === 98 === In the past decade, the awareness of environment preservation and the rapid increase of global oil price have aroused the investigation of new energy resources applied in transportation, portable devices and stationary equipments in the near future. Proton exchange membrane fuel cells (PEMFCs), which employ Nafion® membrane as solid proton conducting membrane, with several advantages such as high energy density, high energy conservation efficiency and near-zero pollutant are recognized as a promising alternative to be widely applied in transportation, residence and portable devices in the near future. However, a severe decrease in proton conductivity of Nafion® membrane is observed when operating temperature increases to 100℃. This phenomenon is attributed to the low hydration level of Nafion® membrane caused by serious water loss at high temperature and, therefore, limits the operation temperature of PEMFCs. Generally, for operating PEMFCs at the temperature higher than 120℃, an external humidifying system used to maintain appropriate hydration level of Nafion® membrane is indispensable. Nevertheless, this excess humidifying system increases the complexity of the PEMFC structure which poses a great obstacle to the commercialization of PEMFCs. Thus, to solve this problem, a versatile membrane electrode assembly (MEA) capable of maintaining optimum hydration level at dehydration conditions without the assistance of external humidifying system is desired This study aims to investigate the feasibility of coating hygroscopic zinc oxide, which used as water adsorbent due to the Lewis acid sites distributed over it surface, on the anodic catalyst layer to main appropriate hydration level at anode under dehydration condition. Different anode humidifier temperatures at 25 ℃, 45 ℃, 55 ℃ and 65 ℃ were designed to investigate the influence of anode humidification conditions on cell performance. The temperature of cell and the cathode humidifier were both fixed at 60 ℃. The polarization measurement was conducted at ambient conditions. It was found that cell with anode catalyst layer coated with 30 seconds zinc oxide revealed the best performance at anode humidifier temperatures ranging from 25 to 65 ℃ due to the smallest negative influence on electronic resistance.