UBC Theses and Dissertations
Improved characterization and movement of the platinum band in a proton exchange membrane fuel cell Damron, David Luke
Proton exchange membrane (PEM) fuel cells are devices that produce zero emission electricity, offering one pathway towards a sustainable energy future. They are in the early stages of commercialization in automotive, backup power and mobile power applications, with cost and lifetime of the cells still representing major barriers. Platinum (Pt) degradation in a PEM fuel cell leads to reduced performance and lifetime, while raw material costs represent a large portion of the overall cost. One of the Pt degradation modes leads to Pt dissolving from the cathode and precipitating in the membrane, forming a “Pt band”. The Pt band is disconnected and unused Pt. If this Pt could be moved, it might be able to be returned to the cathode and be made useful again. This Pt can also have effects on membrane degradation. Pt bands were created in two unique locations using accelerated stress tests (AST) of 10,000 square wave potential cycles from 0.6-1.0V. The locations of the bands were accurately predicted using an existing model and are dependent on the concentrations of oxygen and hydrogen in the membrane. It was hypothesized that increasing the oxygen concentration around the Pt particles in the membrane, would lead to dissolution and movement of the Pt. A new more quantified analysis of the Pt band using SEM imaging is implemented to measure the Pt movement and more fully characterize the Pt band. After two experiments, one trying to move the Pt for 28h and another for 100h, no Pt movement was observed. Another experiment created 2 Pt bands in the same membrane and characterized them for the first time. The second band formed in this experiment did not influence the first band, nor was it influenced by the first band during its formation. The new characterization techniques demonstrated that the distributions of Pt mass and particles were different for the bands formed in the two different locations, while the dual band displayed a superposition of these distributions. The differences distributions have never been quantified before and could have different effects on membrane degradation, which should be the focus of future work.
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Attribution 4.0 International