Effects of Cathode Catalyst Layer Structure and Properties Dominating Polymer Electrolyte Fuel Cell Performance

Abstract

Transport of electrons, protons, and oxygen are necessary for the cathode reactions in polymer electrolyte membrane fuel cells, and achieving the optimum structure of the electrode catalyst layer and the efficient transport of reactants is an effective avenue to reduce the use of platinum catalyst. This study applied three-phase boundary and cathode catalyst layer models to understand details of optimally efficient structures for the transport of reaction components. The factors dominating the effects of the catalyst layer structure and the properties identified in this manner are investigated using the models. Additionally, equations of evaluation are developed to evaluate the effects of the structure and the properties on the cell performance, and the effectiveness of the developed equations is confirmed by a comparison of the results calculated by the equations with the model simulations. From these results, the structure of the porosity, the catalyst layer, and the polymer electrolyte thicknesses, that are optimum for the gas transport and proton conduction, are determined. It is found that the solubility of oxygen in the polymer is one of the dominant factors in the processes of the cathode catalyst layer, and that increasing the solubility is highly effective to reduce the need for platinum

Analysis and modeling of PEMFC degradation: Effect on oxygen transport

“…We found that the oxygen permeation through the ionomer film is a major portion of the total transport resistance through the cathode catalyst layer, especially for low-Pt-loaded catalyst layers. This effect has also been shown in various modeling studies to be a critical issue [17,18]. Therefore, we anticipate that the performance decay might have a similar effect with the oxygen transport resistance.…”

“…One is the calculation result of reducing only A Pt and the other is the calculation result of reducing both A Pt and a eff ion using the relation of Eq. (18). The increase in the proton-transport overpotential is caused by changing the proton-transport distance in the ionomer by shifting the reaction distribution across the cathode CL.…”

Time-Dependent Mass Transport for O2 Reduction at the Pt Perfluorosulfonic Acid Ionomer Interface

“…[13][14][15] Other studies support this contention -that oxygen mass transport resistance through the catalyst layer ionomer plays a large role in determining the power that can be extracted from a fuel cell. 16 It has also been suggested that the total mass transport resistance is exacerbated by a mass transport resistance at the gas/ionomer interface, which becomes increasingly dominant as ionomer film thickness is reduced. [17][18][19] Understanding oxygen mass transport limitations at ionomer | Pt interfaces is therefore of growing interest.…”

Analysis of Cathode Catalyst Layer Structure and Oxygen Transport Resistance Depending on Fabrication Condition in PEFC

“…These decrease the oxygen diffusion resistance in the ionomer and the CL pores. From the previous study (8), the decrease in the oxygen diffusion resistance in the ionomer is considered to be dominant to increase the limiting current density here. On the other hand, in the results with the set (b) (smaller agglomerate size and slower oxygen dissolution rate), the highest limiting current density is achieved with the I/C ratio of 2.0 ( Fig.…”

“…The simplified agglomerate model (8) was applied as the three-phase boundary model of the cathode CL as shown in Fig. 1(a).…”