A Study On The Microporous Layer And Catalyst Layer Of Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell (PEMFC) has wide application due to itshigh efficiency, low noise, fast start-up and environmental advantages. However, thehigh cost and low durability of the MEA hampered its commercialization seriously. Inthis thesis, we studied on the effects of the microporous layer on PEMFC performancewith different surface morphology, carbon material and structure, and preparedcatalyst layer with an alternative electric field to improve PEMFC performance.Blade-coating method and spray method were applied to make the microporouslayer with different surface morphology using carbon black. The surface morphology,in-plane and through-plane resistance and fuel cell performance were measured. Theresults show that the surface morphology of the microporous layer prepared by bladecoating is smoother. The fuel cell with a smoother microporous layer had betterperformance and larger limiting current density.Multi-walled carbon nanotubes (MWCNTs), which have high conductivity andchemical stability, were used to prepare the microporous layer. The effects ofMWCNTs loading on the PEMFC performance were studied. The results show thatthe microporous layer with1.5mg(MWCNTs)/cm2corresponded to the best cellperformance.In order to overcome the surface undulations of the microporous layer preparedwith MWCNTs, both MWCNTs and carbon black were used to fabricate adouble-layered microporous layer. Applying another microporous layer of carbonblack onto the microporous layer made with MWCNTs reduced the surface roughnessof the microporous layer, and formed a gradient pore structure. The PEMFC with thedouble-layered MPL showed a better performance than that with single-layered MPLsunder the same carbon material loading.A catalyst layer with an orientation structure was tried to make by applying analternative electric field to the catalyst ink during its drying process. The response of acatalyst layer to the electric field was tested with a frequency range of0.001~1000Hz under a fixed electric field intensity. The in-plane resistances and electrochemicalsurface area of the catalyst layers treated under different electric field were measured.Catalyst layers treated under the optimum frequency were compared with that made under the general preparation process by the PEMFC performance. The resultsshowed that when treated with an electric field of1Hz, the catalyst layer had thelargest electrochemical surface area. The electrochemical surface area was improvedby67.1%as well as15%to the peak power density.