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Effects of a perfluorosulfonate ionomer (PFSI) and of a polytetrafiuoroethylene (PTFE) loaded carbon (PTFE-C) on the catalyst layer in the electrode of a polymer electrolyte fuel cell (PEFC) prepared by a new method based on the process of PFSI-colloid formation were investigated by electrochemical techniques and a mercury pore sizer. The microstructure of the catalyst layer and its effect on the PEFC performance were affected by the contents of both PFSI and PTFE-C. The catalyst layer has two distinctive pore distributions with a boundary of ca. 0.04 ~m. The volume of larger pore (secondary pore) deceased with an increase of the PFSI content and increased with an increase of the PTFE-C content. The volume of the smaller pore (primary pore) was independent of the content of both PFSI and PTFE-C. The PFSI as well as the PTFE existed only in the secondary pore. The content of PFSI affected the performance of PEFC in the whole current density range. On the other hand, the content of PTFE-C influenced it greatly at high current density due to its gas feeding faculty.In the PEFC, reaction sites were found to exist in the secondary pore coated with the macromolecule PFSI. The hydrophobic PTFE-C works to supply the reaction gas to the reaction sites covered with the PFSI in the secondary pore, and to exhaust the product water from there. The high performance of PEFC at high current density was achieved with the best mixture of the PFSI and the PTFE-C.

A new preparation method for the catalyst layer in the electrodes of a polymer electrolyte fuel cell, based on the process of preparing perfluorosulfonate-ionomer (PFSI) colloid, was developed. In this method, both a good network of PFSI and uniformity of PFSIs on Pt particles were achieved with colloid formation of PFSI chains in the specific organic solvents. The applicable organic solvents had dielectric constants ranging from 3 to 10. The PFSI colloids were selectively adsorbed onto the carbon agglomerates with highly dispersed Pt particles on the surface, and a catalyst paste-formation followed. Then the catalyst paste was spread over a carbon paper representing the gas diffusion layer, and two sheets of carbon paper with catalyst paste on them were hot pressed onto an ion-exchange membrane from both sides. This simple preparation method provided high performance in fuel cells at low temperature (50~

The influence of convection and interfacial-reaction resistance on the response of microsensors, including the effects of: (i) fluid flow rates; (ii) reactant (to be sensed) concentration and diffusion coefficient; (iii) fluid conduit and microsensor size; and (iv) sensor potential and interfacial-reaction resistance, are clarified. For steady-state convective diffusion to a niicrodisk sensor, it is shown that sensor response is a monotonic function of two dimensionless groups: the Péclet number Pe, which characterizes the magnitude of convective transport relative to that of diffusion, and the group tan (8), which provides a measure of diffusive-transport resistance relative to that of the interfacial charge-transfer reaction. A singular-perturbation solution provides the sensor response vs. Pe and 0 for small Pe, corresponding to slow fluid flows and small disks, and numerical calculations extend the analysis to higher Pe values. The analysis suggests a method for increasing the signal-to-noise ratio through altering the sensor bias potential.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 136.167.3.36 Downloaded on 2014-11-02 to IP