Effects of organic solvents on the structure and performance of catalyst coated membrane used in PEM fuel cells

Catalyst coated membrane (CCM) was prepared by direct spraying deposition of the catalyst on the surface of proton exchange membrane, which was then assembled with carbon paper diffusion layers to form a membrane electrode assembly (MEA) for the proton exchange membrane fuel cell (PEMFC). The mixture solution for preparing CCM was composed of 20%(mass ratio) Pt/C catalyst, 5%(mass ratio) Nafion solution, organic solvent and de-ionized water. The surface morphology and pore structure were characterized by the environmental scanning electron microscopy (SEM) and the polarization characteristics of MEA were evaluated by the current-voltage curves of a single PEMFC. The results indicated that the selection of solvent (ethanol, isopropyl alcohol and tert-butyl alcohol) as well as its content and volatility exhibit direct impact on the pore structure of catalyst layers of CCM, which affects the electrochemical performances of MEA. CCM fabricated with isopropyl alcohol solvent and a mass ratio of 4.28 to Nafion solution under 50℃~75℃ exhibits an improved pore structure and I-V characteristic of MEA obtained.