A proposed agglomerate model for oxygen reduction in the catalyst layer of proton exchange membrane fuel cells

Abstract

Citation: ZHANG, X. ... et al, 2014. A proposed agglomerate model for oxygen reduction in the catalyst layer of proton exchange membrane fuel cells. Electrochimica Acta, 150, pp.320 328. Additional Information:• This is the author's version of a work that was accepted for publication in Electrochimica Acta. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Oxygen diffusion and reduction in the catalyst layer of PEM fuel cell is an important process 3 in fuel cell modelling, but models able to link the reduction rate to catalyst-layer structure are 4 lack; this paper makes such an effort. We first link the average reduction rate over the 5 agglomerate within a catalyst layer to a probability that an oxygen molecule, which is 6 initially on the agglomerate surface, will enter and remain in the agglomerate at any time in 7 the absence of any electrochemical reaction. We then propose a method to directly calculate 8 distribution function of this probability and apply it to two catalyst layers with contrasting 9 structures. A formula is proposed to describe these calculated distribution functions, from 10 which the agglomerate model is derived. The model has two parameters and both can be 11 independently calculated from catalyst layer structures. We verify the model by first showing 12 that it is an improvement and able to reproduce what the spherical model describes, and then 13 testing it against the average oxygen reductions directly calculated from pore-scale 14 simulations of oxygen diffusion and reaction in the two catalyst layers. The proposed model 15 is simple, but significant as it links the average oxygen reduction to catalyst layer structures, 16 and its two parameters can be directly calculated rather than by calibration.

Optimization of polymer electrolyte membrane fuel cell catalyst layer with bidirectionally-graded composition

“…They showed good agreement with experiments in predicting the effect of compositional variations within the CL. In addition to these efforts, recently [18] proposed an agglomerate model that employs a distribution function to link the averaged O 2 reduction reaction within the CL to its microstructure.…”

A Review of Computational Fluid Dynamics Simulations on PEFC Performance

“…The oxygen reduction reaction (ORR) is a very important process in fuel cell modelling that occurs at the cathode and the hydrogen oxidation reaction (HOR) at the anode [15,40,41] can be expressed as flows:…”

Method to improve catalyst layer model for modelling proton exchange membrane fuel cell

“…(11) is the rate defined in Eq.(2). It was found in our previous work that ( ) g t can be approximated by the gamma distribution function when the ionomer film is thin [32]. As the ionomer film increases, however, the gamma distribution is unable to describe ( ) g t .…”

“…For practical use, therefore, it is ideal to derive a simple formula that can adequately describe the average reaction rate by explicitly taking all agglomerate processes into account. We made such an effort by assuming that the ionomer film was thin [32]. In this paper, we show how to derive the agglomerate model for a given agglomerate structure by describing oxygen movement and reaction within it as two independent random processes.…”