Molecular Modeling and Experimental Study of Electrocatalytic and Transport Processes in High Temperature Polymer Electrolyte Fuel Cells

摘要

The molecular dynamic simulation correctly predicted the permeabilities of hydroniums and methanol in a temperature range between 20 and 1200C. The calculated conductivity data gradually deviated from the experimental values with increasing temperature. The deviations were much less than one order of magnitude in wide ranges of temperature and humidity. The permeability of methanol in new ABPBI membranes is much lower than that in the Nafion 117 membrane. The ABPBI membrane is thus promising for use as the polymer electrolyte in a high temperature proton exchange membrane fuel cell. The methods that we used for the ab initio atomistic simulations allowed evaluation of the energy barriers for the electrochemical reactions. The ab initio simulation results correlated with the experimental results. We also found that La(1-x)Fe(1-y)O(3-delta)showed significant catalytic activity for methanol oxidation in DMFC. The current sensing atomic force microscopy study allows evaluation of the intrinsic electrochemical activity of electrocatalysts. The results clearly demonstrate that on the catalyst surface areas that are about 20 nanometers to the ionomers are active and the surfaces 50-100 nanometers from the ionomer are not active at all. Only the active sites close to ionomers contribute to the electrocatalysis in a fuel cell.