UBC Theses and Dissertations
Characterization and enhancement of the oxygen evolution reaction in polymer electrolyte membrane water electrolysis Kwan, Jason Tai Hong
In this thesis, novel electrochemical methods for characterizing the oxygen reduction reaction (ORR), the oxygen evolution reaction (OER), and alternative materials for the current collector and flow field for the polymer electrolyte membrane water electrolyzer (PEMWE) are presented. A novel modified rotating disk electrode (MRDE) apparatus used for characterizing catalyst coated membranes (CCMs) for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cell (PEMFC) application was demonstrated first. Cyclic voltammograms (CV) and ORR curves were obtained at room temperature for Pt foil and three commercial CCM samples. The mass activity obtained from the MRDE technique, compared to classical thin-film RDE, were in closer agreement to the PEMFC results. For the OER study, six different current collectors were tested using one commercial CCM in a half cell at 25, 40, 55, and 75°C. The MRDE was able to reach 2 A cm⁻² for commercial OER catalysts. This is a large improvement over traditional OER RDE, which seldom reaches 50 mA cm⁻². There is an improvement in performance with increasing triple contact point (TCP). A transparent visualization cell was developed to expand the channel adjacent to the anode catalyst. This cell was designed to operate current densities higher than 2 A cm⁻², where mass transport effects are more dominant. A commercial catalyst and four Ti current collector meshes were tested at room temperature. Rapid cycling CVs and polarization curves were performed to validate this setup and rank the mesh performance. Fourier transform and bubble-ratio analysis were used to identify characteristic bubble lifetimes. Current density increases with decreasing bubble ratio in the frequency range 0.03 < f < 1 Hz. Finally, PTLs with reduced Ti content, and the concept of a no-PTL PEMWE were explored. Initial results using no PTL on the anode-side show a current density of 2 A cm⁻² at 80°C at 2.5 V when corrected for the area of the channel landing. This highlights the possibility of removing the anode PTL, and focusing the efforts on an engineered flow field, which provides the functionality of a PTL.
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