Nafion Distribution in Gas Diffusion Electrodes for Solid‐Polymer‐Electrolyte‐Fuel‐Cell Applications

Abstract

The location of Nation R in solid-polymer-electrolyte-fuel-cell electrodes was investigated by porosimetry and scanning microprobe analysis. At low Nation loadings, the polymeric electrolyte uniformly fills the micro-and macropores of the electrode structure and increases its ionic conductivity. The pores are completely filled in the range from 0.8 to 1.0 mg of Nafion]cm 2 of electrode, and further addition of polymer results in the formation of a film on the external surface of the electrode. This film causes an additional resistance in series with the ionic resistance in the active layer. Impedance spectroscopic measurements of electrodes with different Nation loadings provided evidence for a variation of ionic resistance with the amount of polymer. The comparison of impedance data with polarization tests indicates that, at least for our formulations, the ionic resistance is the main factor which controls the electrochemical performance. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 155.97.178.73 Downloaded on 2014-11-26 to IP ABSTRACTWe describe a study of the oxygen reduction kinetics at the Pt/recast Nation | interface employing a minicell based on a filmed microelectrode. The experimental conditions are identical to those in polymer-electrolyte fuel cells in that the recast ionomer electrolyte is exposed only to water vapor. We find that the interfacial rate of oxygen reduction near 0.9 V is similar for the Pt/recast ionomer interface and for Pt immersed in dilute aqueous acid solutions. A significant loss of oxygen reduction activity occurs when the recast ionomer electrolyte loses water. We discuss a possible evaluation of catalyst utilization in polymer electrolyte fuel cells.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 155.97.178.73 Downloaded on 2014-11-26 to IP

Electrochemical reaction engineering of polymer electrolyte fuel cell

“…The H 2 and O 2 flow rates were, respectively, 600 and 300 cm 3 /min (208C, 1 atm) on dry basis. Data for use in kinetic analysis were acquired at current densities below 0.6 A/cm 2 at fractional O 2 consumptions less than 3%.…”

“…A standard equivalent circuit model was employed to determine the membrane resistance 3 and the measured membrane resistivity values were 0.23, 0.29, 0.34, and 0.37 X m at RH values of 81.4, 65.8, 52.8, and 33.2%. The measured cell voltage combined with the membrane resistance overpotential (the IR-corrected cell voltage) was regarded as the cathode emf, E cm , at the membrane-CL boundary.…”

Functionally Graded Cathode Catalyst Layers for Polymer Electrolyte Fuel Cells

“…The kinetics of ORR at platinum/polymer electrolyte interfaces has been investigated extensively for several decades [1][2][3][4][5][6][7][8] with the objective of improving catalyst efficiency and reducing voltages losses. 9,10 High efficiencies for ORR with electrodes containing low platinum loadings have been achieved by incorporating Nafion ionomer into the matrix of carbon-supported Pt/C. [11][12][13] Cathode catalyst layers in PEFCs are thin films sandwiched between membranes and gas diffusion layers ͑GDL, carbon paper or carbon cloth͒.…”

The colloidal tool-box approach for fuel cell catalysts: Systematic study of perfluorosulfonate-ionomer impregnation and Pt loading

“…Further addition of ionomer results in a formation of films on the surface of the electrode (pores are reported to be completely filled in the range from 0.8 to 1.0 mg of Nafion/cm 2 of electrode). As the ionic resistance of this film is higher than the Nafion membrane, this increases the overall ionic resistance of the electrode [9][10][11][12]. Furthermore, since the ionic conductivity of the ionomer is high for protons, but its electric conductivity is very low, a surplus addition of ionomer leads to an increase in proton conductivity at the expense of electronic conductivity.…”

“…25-30 wt. % Nafion, depending on the preparation route, is used in the catalyst layer in MEA studies [4,9,[13][14][15].…”