A Study On The Graphene Coated Aluminum Bipolar Plates In Proton Exchange Membrane Fuel Cells

Aluminum is a good candidate of bipolar plates for proton exchange membrane?PEM?fuel cells,because of its high electrical and thermal conductivity,low specific weight and excellent manufacturability.However,aluminum is easily corroded in the humid and acidic environment of PEM fuel cells,so various schemes of protective coating were investigated.Such a coating proves to be very challenging as it needs to be simultaneously corrosion resistant,electrically conductive as well as low in interfacial contact resistance?ICR?.For the first time,we have attempted to coat graphene on aluminum substrate for application to bipolar plates in PEM fuel cells.By simply immersing an aluminum sheet in an aqueous solution of graphene oxide?GO?,a layer of cross-linked GO gel forms on the aluminum sheet,taking advantage of dissociated aluminum ions as a cross-linker.Then the cross-linked GO is reduced to graphene at high temperature in hydrogen atmosphere.The influences of immersion and reduction conditions on the resulted graphene films were investigated.The sample in the best condition shows a corrosion current density of<1×10^-66 A/cm²,which is around three to four orders of magnitude lower than a bare aluminum sheet.Meanwhile,the graphene film on aluminum results in a much lower and more stable interfacial contact resistance?ICR?of 6.4 m?·cm² and higher vertical conductivity of 151 S/m.These enable the graphene coated aluminum sheet to meet the U.S.DOE targets of 2020 for bipolar plates in terms of both the corrosion and electrical resistance.To make the coating process more time efficient,Cwas added to GO solution to accelerate GO crosslinking on aluminum substrate.The immersing time need was shortened by 25%.Besides,the reduction of GO at low temperature usingRegent A was tried and the influence of the factors in??A reduction on the resultant graphene films were studied.It is found that the low temperature reduction by Regent A is especially suited for the GO film crosslinked by C.The sample prepared in the optimum condition shows a corrosion current density of<1×10^-6A/cm².In addition,the an ICR of 4.8 m?·cm² and vertical conductivity of 142 S/m can be achieved,well meeting the U.S.DOE targets of 2020.Thus the proposed method is very promising for protecting aluminum bipolar plates in PEM fuel cells.