Study On Bionic Flow Field Active Drainage Mechanism And Surface Modification Of Proton Exchange Membrance Fuel Cell Bipolar Plate

Proton exchange membrane fuel cell?PEMFC?is likely the most promising generation of power source,on account of its high current density,light weight,zero emission,low working temperature,fast start and long lifetime.A bipolar plate is a key component in PEMFC,which requires high conductivity and corrosion resistance,and helps to distribute reactant uniformly and remove superfluous water efficiently.In this work,the idea of active drainage flow field was proposed and verified.Combined with bionics leaf-inspired structure,active drainage leaf-inspired flow field was designed and optimized.Meanwhile,stainless steel?SS?bipolar plate was modified with amorphous carbon?a-C?film.Finally,bipolar plate was prepared,and single fuel cell was assembled and tested for electrical performance,lifetime and dynamic characteristics.Main contents are as follows:?1?Based on interdigitated flow field,the top face of outflow channel was replaced with drainage pressure inlet.Current density and water distribution were compared with that of interdigitated flow field to confirm the feasibility of active drainage flow field.And then,the effects on current density,pressure loss and net output power density of inlet pressures of anode and cathode were studied to optimize the best choice of pressure setting.Compared with interdigitated and serpentine flow field,standard size active drainage flow field was given to investigate performance under different oxidizing agent and emphasize the feasibility and superiority.?2?Leaf-inspired structure was adopted for flow field configuration,and active drainage leaf-inspired flow field was designed with equal-length branches.Current density,pressure loss,reactant and water distribution under different oxidizing agents were investigated to understand the inner mass transfer phenomena and distribution characteristics.Combined with effects of rib width in interdigitated flow field,the flow field was optimized with shorter branch length and gradually shortened rib width to drain the reactant to far end and improve low current density there.Finally,the inner distribution uniformity was enhanced and the flooding problem was solved,with high output current density of 2370.28mA·cm^-2 under operating voltage 0.3V.?3?Chromium interlayer amorphous carbon?Cr/a-C?was adopted for surface modification.The interface between chromium interlayer and a-C film was interlock structure and the contact angle with water was 89.5°.The electrical resistivity was 2.73×10^-6?·m and the interfacial contact resistance under compaction force of 150N/cm² was 16.65 m?·cm².The corrosion resistance of Cr/a-C film was excellent,with corrosion potential of-0.32V and corrosion current density of 14.5?A·cm^-2.The current density of Cr/a-C went close to 0 and stabilized at negative.?4?Single fuel cell with active drainage leaf-inspired flow field Cr/a-C 304SS bipolar plate was assembled to test performance and stability.The experimental results fitted numerical simulation data well.Lifetime test showed the Cr/a-C film was stable during 12h with no observed degradation.Dynamic characteristics test shows that the response time of optimized active drainage leaf-inspired flow field was 0.8s when the operating voltage was changed.Performances of active drainage leaf-inspired flow field were studied via simulations and experiments in this paper,which provides certain guidance for design and manufacturing of PEMFC.