Studies On The Formation Of Catalyst Layers Using Electrohydrodynamic Atomization Deposition For Direct Methanol Fuel Cells

Direct methanol fuel cell (DMFC) is regarded as a promising power source for portable power supply due to its higher energy density of the system, convenience in storage and simplicity in structure. Catalyst layer is a core function layer of DMFC, served as the place for electrochemical reaction. The structure of catalyst layers has a great effect on cell performance. Electrohydrodynamic atomization (EHDA) is a technique which can be used for prepare film by layer by layer (LbL) deposition. In this work the catalyst layers with different pore structure were deposited using EHDA LbL deposition at different atomization parameters. The performance of single cells assembled with the EHDA LbL deposited catalyst layers was analyzed.The EHDA equipment was designed and set-up, which was computer-controlled using Labview software. C nano-suspension was atomized using EHDA technique and various atomization modes were formed and discussed. Boundary condition form the formation stable cone-jet mode was obtained.Pt/C and Pt-Ru/C nano-suspension were atomized and deposited in stable cone-jet mode using EHDA. The effect of the atomization parameters including applied voltage, flow rate and working distance on size and distribution of the deposited droplets and structures of Pt/C and Pt-Ru/C films were examined. The results showed that the flow rate and working distance had great influence on the size and distribution of the droplets, while the applied voltage was inconspicuous. The lower flow rate and higher working distance resulted in smaller size and lower number density of relics, and formed larger porosity of films which present dendritic and well-packed structure. Conversely, higher flow rate and lower working distance generated bigger droplet size and higher number density, and resulted in dense films corresponding. The influence of the atomization parameters including flow rate and working distance on the porosity of Pt/C and Pt-Ru/C films were calculated.Cathode catalyst layers with different pore structure were produced on Nafion film using EHDA LbL deposition at different working distances. Anode catalyst layer was prepared at a constant working distance. The Pt-Ru and Pt loadings of anode and cathode catalyst layers were1.2mg-cm-2and0.4mg·cm-2respectively. And the MEA active area was20mm×20mm. The effect of the catalyst layer’s porosity on performance of DMFC was studied using electrochemical methods. The results showed that with the working distance increasing from 3mm to7mm the cathode catalyst layers became more porous. The cell assembled with cathode catalyst layer with larger pores present larger active area for electrochemical reaction and greater performance. The peak power density of the cell assembled with the cathode catalyst layer deposited at a7mm working distance was66.2mW·cm-2under a cell operating condition of80℃and oxygen feedings. And the specific power was41.4mW-mg-1(Pt and Ru).