Study On Surface Modification And Characterization Of Carbon-based Films On PEMFC Stainless Steel Bipolar Plate

The bipolar plate is one of the most critical components of proton exchange membrane fuel cell, which accounts for a large proportion of quality and cost in the fuel cell stacks. Metal bipolar plates especially stainless steel, has won much attention of scholars for its excellent electrical and thermal conductivity, easy molding and low cost. But the oxide layer generated on the surface performs poor conductivity, also it can be easily corroded under the operating environment of fuel cell. It is a key element to improve its performance and to solve the problem of its large-scale applications by surface coating technology on stainless steel substrate.In this paper, we use complex magnetic filtered cathode arc apparatus to deposit films on the 304 stainless steels, and then select the best one to make optimization of the process to achieve the modified material with best performance. The results show as follows:1) Make comprehensive comparison of the conductivity and corrosion resistance of different materials and found that amorphous carbon film has the best electrical properties, also has excellent corrosion resistance.2) The incident energy of the ion bombardment plays a vital role during the preparation of the amorphous carbon films, which directly affects the microstructure of films and then affects its corrosion resistance, electrical conductivity. By selecting bias of-50 V,-200 V,-350 V, found that under the bias of-200 V, thin films achieve the highest sp2 content and best compactness, performing the best electrical conductivity and corrosion resistance.3) Carbon films will peel from the stainless steel substrate easily when directly depositing on the substrate because of the poor binding force between them. Metal transition layer can not only enhance their binding properties with the matrix, but also have great impact on the microstructure and performance of carbon films. By comparing several common metals used as transition layer(Cr, Ti, W), found that carbon films with Cr as the transition layer perform the best conductivity and corrosion resistance.