Construction And Performance Of Novel Protonic Membranes And Gas Diffusion Layers For High Temperature PEMFCs

High temperature proton exchange membrane fuel cell(HT-PEMFC)has become one of the current research hotspots because of its advantages such as strong CO resistance and simple hydrothermal management due to its operating temperature above100°C.As the“heart”of HT-PEMFC,the membrane electrode(MEA),which mainly composed of proton exchange membrane(PEM),catalytic layer(CL)and gas diffusion layer(GDL),directly determines the performance of HT-PEMFC.This research focuses on the preparation and performance of novel PEM and GDL as well as the resulted MEA.The main conlusions are as follows:(1)The in-situ synthesis method was used to synthesize poly 2,5-benzimidazole(ABPBI)molecular chain on the end group of polysilsesquioxane(POSS)to prepare ABPBI-POSS composite membrane with star structure.Compared with pure ABPBI membrane,the advantages of composite membrane are as follows:1)The entanglement of molecular chains is untied,resulting in the decrease in polymer viscosity and the increase in film-forming performance;2)Increase the free space inside the polymer to improve the water and acid absorption performance,thereby the proton conductivity is improved.The results show that the ABPBI-1.0POSS composite membrane has the advantages of low viscosity and high mechanical properties,and its proton conductivity reaches 0.022 S/cm without humidification at 180°C.(2)Polyaniline(PANI)nanowires were prepared in situ on the surface of carbon paper by an electrochemical method,and then hydrophobicized to obtain a reticulated PANI-S based GDL,which was used to reduce the mass transfer resistance of MEA cathode.Compared to the conventional XC-72 based GDL prepared with conductive carbon black,the porosity of PANI-S based GDL increased from 65.2%to 77.7%,and the thickness decreased from 236?m to 193?m.These advantages will help to improve the power density of HT-PEMFC.(3)For the problem of HT-PEMFC single cell performance test,this thesis designed and built an HT-PEMFC test system.At the same time,the HT-PEMFC test conditions were optimized from the aspects of gas metering ratio,gas pressure and temperature.Finally,the power density of the MEA prepared with the ABPBI-1.0POSS composite membrane reached 570 mW/cm~2,which was nearly 22%higher than the 469mW/cm~2 of the pure ABPBI membrane.And the power density of the MEA prepared with ABPBI-1.0POSS composite membrane and PANI-S basd GDL further increased to712 mW/cm~2.