| Proton Exchange Membrane Fuel Cell （PEMFC） is a device that directly converts the chemical energy of the fuel and oxidant into electrical energy. It is recognized as the most promising power generation technology in the 21st century. Bipolar plate is the one of critical component of the PEMFC, which directly affects the output power and life time of the cell stack, and the cost accounts for about 46 percent of the total cost of a cell stack, while the high cost of PEMFC is a key obstacle to its wide application.To accelerate the commercialization of PEMFC, the bipolar plates with high performance and low cost are explored, and the polymer/graphite composite bipolar plate is a promising alternative, which has received significant attention for fuel cells. In this study, the modification and performances of composite bipolar plates were investigated. Meanwhile, considering the development of bipolar plates in the future, the attempts were carried out in the materials and process of composite bipolar plates based on bamboo charcoal.In this study, the performances of bipolar plates improved significantly by adding coupling agents and carbon fiber, and the influences of types, treating methods and mass fraction of coupling agents on the properties of bipolar plates were explored, as well as that of mass fraction and surface modification of carbon fiber. Results show that the application of coupling agent is benficial for enhancing the mechanical strength, which possess the optimum value with the variation of coupling agent content, while the conductivity of composite tends to decrease rapidly. And it is apparent that the graphite modification is significantly better than resin modification in enhancing flexural strength of bipolar plates, which results in the conductivity decreasing more sharply. Considering the conductivity and mechanical properties of composite bipolar plates, it can be concluded that the resin modification is more suitble for fabrication of composite bipolar plates. Moreover, the two different coupling agent affect the mechanical strength to the same extent, and the composites modified by titanate coupling agent possess better conductivity than that modified by silane coupling agent due to the difference of molecular structure between them. Additionally, carbon fiber is considered as an effective additive to enhance the mechanical properties of composite bipolar plates, however the conductivity and compactness of composites decrease slightly with increasing of carbon fiber content. The composite bipolar plates, adding carbon fiber treated by concentrated sulphuric acid and coupling agent, can exhibit higher performances due to the reinforcement of interfacial compatibility between carbon fiber and matrix, and the permeability of composite bipolar plates above are measured at 10-710-6 cm3·（cm2·s）-1,which can be basically up to the DOE target value. And these bipolar plates have good thermal stability in PEMFC working temperature 80100℃.Additionlly, the microstructure and properties of bamboo charchoal as a function of temperature were measured. And the bamboo charcoal/phenolic resin composite bipolar plates were prepared by compression molding technology, using bamboo charcoal graphitized at 2800℃as conductive filler, phenolic resin as binder and carbon black as additive. The influences of particle size of bamboo charcoal, resin content, adding way and content of carbon black, molding pressure and curing temperature on the properties of the composites were investigated. Results reveal that the optimum praticle size, mass fraction of resin, mass fraction of carbon black, molding pressure and curing temperature should be≤75μm, 30%, 5%, 280 MPa and 180℃, respectively. Due to the porous structure, the conductivity of composite bipolar plate based on bamboo charcoal is apparently lower than the DOE target value, which is regarded as a promising material. |
