Influence of graphite powder on the properties of carbon paper for proton-exchange membrane fuel cells

A PAN-based carbon fiber paper preform prepared by a dry casting method was impregnated with phenolic resin mixed with graphite powder, which was mold-pressed, cured, carbonized and graphitized to prepare carbon paper for proton-exchange membrane fuel cells (PEMFCs). The effect of graphite powder content on the properties of the carbon paper was investigated. Results showed that the thickness, porosity, permeability and conductivity of the carbon paper increased with increasing content of graphite powder while its density and tensile strength exhibited a maximum. The carbon paper has an optimum performance for PEMFCs with a graphite addition of 5 wt.%. The optimized properties of the carbon paper are as follows: thickness 0.23 mm, density 0.53 g cm−3, resistivity 2.6 mΩ cm−1, tensile strength 19.4 MPa, porosity 66%, gas permeability 2 080 mm cm−2 h−1 mmAq−1. The output voltage of a single cell with this paper loaded with 0.5 mg Pt/cm2 was 0.65 V with a current density of 800 mA cm−2 under atmospheric pressure and 65 °C using a H2/air pair.