Research On Surface Modification Of Titanium Bipolar Plates For Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cell(PEMFC),as a new type of power battery,has the advantages of high efficiency,energy saving,zero emission and no pollution and so on.It has been paid much attention by the society and is considered the most potential clean and efficient new energy conversion device to convert the chemical energy of fuel and oxidant into electric energy through electrochemical reaction.It can be widely applied in electric vehicles,space shuttle,submarine,communication system,small and medium sized power station,household power supply,and other places which need mobile power.The bipolar plate serves to separates the anode and cathode oxygen in the fuel cell to provide the flow field and conduct the current for the fluid.To achieve the above functions,bipolar plates should have the advantages of high conductivity,strong corrosion resistance,high mechanical strength and high thermal conductivity.The bipolar plate of fuel cell is divided into three categories:metal bipolar plate,graphite bipolar plate and composite bipolar plate.Compared with other two kinds of bipolar plate,the metal bipolar plate has a great potential of application,such as strong conductivity,good processing performance,high mechanical strength and low cost.However,the corrosion resistance of metal bipolar plates is relatively weak and its surface is easy to produce oxide.In this thesis,the TiN coating modified by Ti bipolar plates was in situ reacted by chemical vapor deposition for the problems of metal bipolar plates.Scanning electron microscope(SEM)display the TiN layer formed by the surface reaction in situ growth in a step growth method.The TiN film constantly covers the metal grain boundary and covers the titanium surface uniformly and compactly.The direct current surface resistance and interface contact resistance(ICR)are used to evaluate the conductivity of coating.The experimental results show that the TiN coating with a 2h in situ reaction time is excellent.And the surface contact resistivity is stable at 6.7m?·cm2 when the pressure is 120 N/cm 2,which meets the standard of the US Department of energy in 2020(ICR is less than 10m?·cm2).The surface corrosion current density is 0.816 ?A/cm2.The corrosion current density(38.9 ?A/cm2)of the TA2 titanium plate decreased by an order of magnitudeIn this paper,a low cost method is also applied to produce amorphous carbon coating.The carbon precursor film is formed on TA2 alloy using glucose through hydrothermal method.Amorphous films are obtained by carbonization at low temperature argon atmosphere.The X ray diffraction pattern(XRD),infrared spectroscopy(FTIR)and transmission electron microscope(TEM)analysis show that the coating is amorphous junction.Carbon coating is used to cover the surface of TA2 alloy evenly.In the simulated proton exchange membrane fuel cell(PEMFC)environment,the corrosion current density of the amorphous carbon coating is 7.537×10-7A/cm2,and the constant potential results show that the coating is stable.Moreover,amorphous carbon coatings also show lower ICR values,all reaching the standards of the US Department of energy in 2020.It is found that the amorphous coating shows good interfacial conductivity,strong corrosion resistance and high potential application in the surface modification of metal bipolar plate of fuel cell.