Studies On Fabrication Of Membrane Electrode Assembly And Cathode Structure For Direct Methanol Fuel Cells

Membrane & electrode assembly (MEA) is the core component of direct methanol fuel cell (DMFC). Up to now, the performance of MEA is still one of the factors which inhibit the commercialization of DMFC, so fabrication of high-performance MEAs is very important for the research and development of DMFC.In this dissertation, the modified decal method was developed to prepare DMFC electrodes. The electrode morphology, particle size of the electrocatalyst, electrochemical active area, resistance and performance of MEAs prepared by the decal and brush methods were compared. The enrichment of ionomer close to the surface of the cathode catalyst layer was studied and possible mechanisms were also proposed. The effect of ionomer content close to the surface of the cathode catalyst layer was explored.The pore structure and hydrophobic property of the cathode were optimized by double-layered structure and carbon black additive, respectively. A novel double-layered cathode catalyst layer for DMFC was prepared, which consisted of Pt black inner catalyst layer and 20wt.% Pt/C (or 40wt.% Pt/C) outer catalyst layer. Due to the intrinsic properties of the two electrocatalysts, hydrophobic property, porosity and catalyst gradient were formed in the cathode. The double-layered structure was beneficial for oxygen diffusion and water removal, the maximum power densities of 254.8 and 176mW/cm~2 were achieved under 2atm oxygen and air at 90°C, respectively. The effect of...