Preparation And Characterization Of Carbon Fiber Paper For Fuel Cell

Proton exchange membrane fuel cell(PEMFC) is one of the most potential clean energy. Gas diffusion layer(GDL) is a key component in PEMFC. Due to its excellent performance and mature paper-making process, carbon paper has been widely used as GDL. Carbon paper has been commercialized in some foreign companies. Some groups reported that carbon paper has been prepared in their lab in China. However, there are still no commercial products until now. Therefore, it is very important to study the preparation of carbon paper systematically.In this paper, carbon paper was prepared by a traditional wet paper-making method. The processes of beating, impregnating with phenolic resin, molding, carbonization and graphitization were investigated systematically. Meanwhile, the carbon paper was modified by chemical vapor deposition(CVD) methods, and the properties and structure of the obtained carbon paper were characterized. The main conclusions of our work are summarized as follow:1. Carbon paper precursor has an important influence on the carbon fiber paper.The different length of carbon fiber was selected in order to increase isotropy of carbon paper precursor. The concentration of dispersant and beating time impact on the thickness and resistivity of carbon paper precursor. Using 0.12% Polyacrylamide (PAM) solution for dispersion of carbon fiber and 8min for beating time can get the good performance carbon fiber paper precursor.2. Impregnating and hot pressing process impact the thickness and resistivity of the carbon green paper. The optimal molding conditions were as follow:impregnating solution 10% ethanol-phenolic resin solution, pressing time 4-5min, pressing temperature 160℃, the thickness of prepared carbon green paper was 185±5μm, resistivity was 5.7×10-2Ω·cm.3. The processes of carbonization and graphitization have rarely effects on carbon paper products. However, the resistivity greatly reduced, conductivity improved. The optimal conditions were:carbonization temperature 900℃graphitization temperature 2500℃, keeping for 30min. The properties of carbon paper are:thickness 185±5μm, resistivity 8.09×10-3Ω·cm,contact angle 136°,porosity 76%。4. The modified carbon paper was prepared, on which the CNTs were growed on the surface of carbon paper by CVD. It has a lower resistivity and higher porosity. At the same time, the surface hydrophobicity was improved. The properties of modified carbon paper were:resistivity 5.81×10-3Ω·cm, contact angle 147°, porosity 82%.