The Dynamics of Platinum Precipitation in an Ion Exchange Membrane

TL;DR

This paper presents a physics-based model explaining platinum precipitation dynamics in fuel cell membranes, predicting platinum band location based on gas conditions and matching experimental observations.

Contribution

The paper introduces a novel model that accurately predicts platinum band formation and movement in polymer electrolyte membranes under various gas conditions.

Findings

Platinum band location depends on gas concentrations and humidity.

Model predictions align with experimental platinum distribution data.

Band shifts towards anode with increased oxygen or decreased hydrogen.

Abstract

Microscopy of polymer electrolyte membranes that have undergone operation under fuel cell conditions, have revealed a well defined band of platinum in the membrane. Here, we propose a physics based model that captures the mechanism of platinum precipitation in the polymer electrolyte membrane. While platinum is observed throughout the membrane, the preferential growth of platinum at the band of platinum is dependent on the electrochemical potential distribution in the membrane. In this paper, the location of the platinum band is calculated as a function of the gas concentration at the cathode and anode, gas diffusion coefficients and solubility constants of the gases in the membrane, which are functions of relative humidity. Under H2/N2 conditions the platinum band is located near the cathode-membrane interface, as the oxygen concentration in the cathode gas stream increases and/or the hydrogen concentration in the anode gas stream decreases, the band moves towards the anode. The model developed in this paper agrees with the set of experimental data on the platinum band location and the platinum particle distribution and size.