Effects of Microstructure of Carbon Support in the Catalyst Layer on the Performance of Polymer‐Electrolyte Fuel Cells

Abstract

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

The Influence of Pt Loading, Support and Nafion Content on the Performance of Direct Methanol Fuel Cells: Examined on the Example of the Cathode

“…0, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]However, the optimum N/C ratios are found to be lower, namely 0.7 and 0.5 for the VC and HG supports, respectively. The optimum N/C value using VC as catalyst support is essentially the same as reported by Liu and Song et al [19,20] i.e.…”

“…This difference may be due to differences in the pore-size distribution of the supports. Uchida et al [9] reported that improvement of DMFC performance can be achieved using a carbon support with a large pore volume, which is able to distribute the Nafion ionomer over the Pt particles inside the carbon support agglomerates. Figure 9 shows the Nyquist plots for the total cell impedance using KB-60, VC-60 and HG-60 cathode catalysts.…”

“…The catalyst support material should have high electronic conductivity, high stability against corrosion, and preferably a mesoporous structure to allow for effective catalyst deposition, fuel access and water management [8]. Uchida [9,10] reported the effects of the microstructure of the catalyst layer on the performance of polymer electrolyte fuel cells (PEFCs) and reported that the pore-size distribution of the carbon support influences the performance of the fuel cell.…”

“…Thus, the reaction area is limited to the interface between the electrode and the membrane. As a result, the electrodes have low catalyst utilization and need high catalyst loadings [9,15]. Solutions of Nafion are impregnated into the electrode catalyst layer to increase the contact area between the Pt catalyst and the Nafion ionomer.…”

“…Solutions of Nafion are impregnated into the electrode catalyst layer to increase the contact area between the Pt catalyst and the Nafion ionomer. In this way, the Pt utilization can be increased, resulting in higher FC performances if an optimum amount of ionomer is used [9][10][11][12][13][14].…”