Fabrication and evaluation of composite bipolar plate to develop a compact and lightweight direct methanol fuel cell stack

A bipolar plate is a major component of a fuel cell stack, occupying a considerable portion of the overall stack cost and weight. In this study, a composite bipolar plate is designed and fabricated to develop a compact and lightweight direct methanol fuel cell (DMFC) stack for small-scale Unmanned Aerial Vehicle (UAV) applications. The composite bipolar plates for DMFCs are prepared with two different natural graphite particles, phenol resin and carbon black (CB) and fabricated by compression molding method. Then, the bipolar plates are tested in terms of electrical conductivity, mechanical strength and hydrogen permeability. The flexural strength of 63 MPa and the in-plane electrical conductivities of 191 S/cm are achieved under the optimum composition of bipolar plate materials with 18 wt.% phenol resin, 82 wt.% natural graphite, and 3 wt.% CB, which demonstrates that the composite bipolar plates exhibit sufficient mechanical strength, electrical conductivity and gas impermeability to be applied in a DMFC stack. A DMFC with the composite bipolar plate is tested and shows a superior cell performance as compared with a DMFC with a typical pure graphite-based bipolar plate.