The application of composite membranes for high temperature polymer electrolyte membrane fuel cell has attracted interests. Nafion-metal dioxide composite membranes are considered among the research niche. In this study, Nafion membranes and Nafion-zirconia composite membranes with 1, 3 and 5 wt. % of hydrous zirconia were prepared accordingly. All membranes were characterized by quantitative analysis techniques such as thermogravimetry analyse, diffraction scanning calorimetry and Fourier transform infrared. All composite membranes showed high glass transition temperatures and improved water retention properties, compared to the Nafion membrane. The composite membrane with 3 wt. % of zirconia showed the highest thermal resistance at 90°C.Keywords: high temperature PEM, glass transition temperature, conductivity, composite membrane, Nafion-zirconia Abstrak Penggunaan membran komposit dalam operasi sel bahanapi membran penukar proton pada suhu tinggi semakin mendapat perhatian pengkaji. Membran komposit Nafion-logam dioksida adalah antara bidang kajian dalam kumpulan ini. Bagi kajian ini, membran Nafion dan membran komposit Nafion-zirkonia dengan 1, 3, dan 5 wt. % telah disediakan. Kesemua membran dicirikan menggunakan teknik analisis kuantitatif seperti analisis termogravimetri, kalorimetri imbasan kerbedaan dan Fourier inframerah. Kesemua membran komposit mempunyai suhu peralihan kaca yang tinggi dan keupayaan penahanan air yang lebih baik berbanding membran Nafion. Membran komposit dengan 3 wt. % zirkonia menunjukkan ketahanan suhu tinggi pada suhu operasi 90°C.Kata kunci: PEM suhu tinggi, suhu peralihan kaca, konduktiviti, membran komposit, Nafion-zirkonia Introduction Fuel cells are electrochemical devices which convert the energy from the reaction of fuel and oxygen into electric energy continuously with water and CO 2 as the byproducts [1]. Polymer electrolyte membrane fuel cell (PEMFC) is one of the fuel cell types, for temperature ranging from 60 -100 °C. Nafion membranes are the most commonly used polymer electrolytes in PEMFC application as it has excellent chemical, mechanical and electrochemical properties as well as high proton conductivity at ambient temperature and high humidity condition. This waterbased electrolyte needs to be kept in a hydrated condition for the best performance and a maximum conductivity of 0.083 S/cm at 100% relative humidity (RH) [2].

Polymer electrolyte membrane based on Nafion and zirconium oxide (ZrO2) was developed via film casting method. The content of ZrO2 (1.0, 2.0, and 3.0 wt.%) was incorporated with Nafion solution to prepare Nafion-ZrO2 composite membranes. Recast Nafion membrane was used as reference material. All of the prepared membranes have been subjected to both physical and chemical characterizations such as Fourier transform infra-red (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) analysis, water uptake rate (WUR) and conductivity measurements. The Nafion-ZrO2 composite membranes were found to possess high thermal stability (Tg= 188 - 192°C) and conductivity (0.30 – 0.93 S cm-1). This study demonstrates the possibility of developing Nafion-ZrO2 composite membrane as promising polymer electrolyte membrane for fuel cell operated at medium temperature and low humidity.