A novel self-humidifying composite membrane for the proton exchange membrane fuel cell (PEMFC) at low humidity condition was developed. The Pt/TiO₂ catalyst particles were synthesized via supercritical impregnation methods. Pt precursor was dissolved in supercritical carbon dioxide and impregnated onto TiO₂ particles. Pt precursors were platinum(II) acetylacetonate, Dimethyl(1,5-cyclooctadiene) platinum(II) and we controlled the ratio of Pt to TiO₂. The impregnated Pt precursor was converted to TiO₂ supported Pt nanoparticle under various reducing conditions. Pt/TiO₂ catalyst particles were dispersed uniformly into the Nafion solution, and then Pt/TiO₂/Nafion composite membrane was prepared using solution-cast method. The self-humidifying composite membrane could minimize membrane conductivity loss under dry conditions due to the presence of catalyst and hydrophilic Pt/TiO₂ particles.
To optimize the performance of MEA, amount of ionomer loading was controlled. And mixed catalysts were used. The cell performance of MEA was obviously improved under both humidified and dry conditions at 65 ◦C.