Surface Modification Of Stainless Steel Bipolar Plates For PEMFC

The bipolar plate is one of the core components of a fuel cell.At present,the performance of the graphite double pole is excellent,but the volume is not suitable for the use of small cars.The power density of metal bipolar plate is high,and it has a better practical application prospect.Two kinds of surface modification of 316L stainless steel bipolar plates were studied in this paper.(1)The TiC modification of the stainless steel bipolar plate is studied as follows:firstly,the surface of the stainless steel was removed and the roughness was adjusted.Then the physical vapor deposition of Cr and Ti by magnetron sputtering was used.Finally,the sputtering of the titanium target was kept at the same time as CH4,and the modified coatings were prepared by means of physical vapor deposition and chemical vapor deposition.When the ratio of argon to methane was 1:1.5,the coating was mainly composed of TiC,a small amount of graphite and Ti,and had the best performance.The contact resistance of the sample is reduced to 13.3 mΩ·cm2,which is 15.6 times smaller than that before the modification;the test results of the dynamic potential and the constant potential polarization curve are all close to the commercial sample,and the corrosion resistance is good;the contact angle is 132.8°degree better than the commercial sample 99.1°.Through the analysis of XRD,EDS and XPS,the samples of argon and methane flow ratio of 1:1.5 eventually formed a modified coating with a mixture of TiC and a small amount of graphite and Ti.(2)The study of the modification of the stainless steel bipolar plate is as follows,first,the mixture of carbon powder and PVDF pyrrolidone was sprayed on the stainless steel bipolar plate,which had been adjusted at 80℃,then the spray plate was heat treated at 330℃.The performance of modified bipolar plate was tested and compared with commercial samples.The sample with a carbon content of 70%has the best performance,its contact resistance is only 1.7 mΩ·cm2,close to commercial samples,the contact angle is 139.2°,and the corrosion voltage is 0.135 V,higher than the commercial sample-0.068 V,after the fitting,the corrosion current density is reduced from 39.81 to 1.72 pA/cm2;after constant potential polarization 14400 s.The current is 2.250 μA/cm2,which is close to 2.208 μA/cm2 of commercial sample.The porosity of modified coating is low and has little effect on corrosion resistance and adhesion.The modified coating with carbon content of 70%was compact and uniform.After constant potential polarization,the morphology did not change significantly.Therefore,the stainless steel modified bipolar plate with 70%carbon content prepared by spraying method has the characteristics of simple preparation,less material and easy to get,less contact resistance,good corrosion resistance and excellent hydrophobicity,which provides a basis for commercialization.