A new class of proton-conducting ceramic composite membranes was developed for lowtemperature fuel cells. According to characterizations, these membranes demonstrated good mechanical, structural, thermal and textural properties. Moreover, they yielded a maximum proton conductivity of 10" 2 S cm" 1 at room temperature. An electrode consisting of a heteropolyacid dispersed in a catalyst layer was also prepared and characterized, and the cell performances when using composite membranes of PWA/PMA doped with Zr0 2 /Ti02 together with an electrode contain heterpolyacid were extremely high as compared to counterparts with a phosphosilicate electrolyte at room temperature. The cell evaluation was performed on PWA/PMA-T1O2-P2O5-SรO2 and PWA/PMA-Zr02-P205-Si02 composite membranes with hydrogen and oxygen. These membranes presented the best properties.
[.INTRODUCTION
At the present time, environmental issues due to increasing emissions of air pollutants and greenhouse gases are spurring the development of technologies for the delivery of clean energy, such as fuel cells. Low-temperature proton exchange membrane fuel cells (PEMFCs) use hydrogen as fuel and their only emission is water. Over the last decade, the interest for utilizing ceramic materials as possible electrolyte membranes for fuel cell applications has grown. 1 " Ceramics are good candidates for electrolyte materials for PEMFCs because of their thermal, chemical, and mechanical stability, as well as their lower material costs.
The proton conduction is highly dependent on the coverage of adsorbed water on the surface of the inorganic material. While significant advances have been made in recent years, a major limitation of the current technology is the cost and material restrictions of the proton conduction membrane. For transport applications, fuel cell companies require more durable, cost effective membrane technologies that are capable of delivering enhanced properties at low temperatures (from room temperature up to 80 ยฐC). As a result, research is being driven towards a wide range of novel organic and inorganic materials showing a potential of being good proton conductors and forming coherent membranes. However, Nafionยฎ and similar membranes suffer serious disadvantages such as high cost, poor hydrophilicity, fuel crossover, low proton conductivity at low humidity and high temperature.
Attempts have been made to produce cheaper proton-conducting membranes that can equal the electrochemical performance of perflourinated ionomers as well as their mechanical, thermal and electrochemical stability. Membranes fabricated from the heteropolyacid (HPA) family are currently the best suited for proton conduction at both low and high temperatures. This paper describes the synthesis and structural properties of novel proton-conducting ceramic composite membranes based on heteropolyacids. Such materials are both cheaper and more thermally stable than Nafionยฎ.