(600bd) Comparison of in-Situ Hydrogen Oxidation Reaction Kinetics for Various Polymer Hydroxide Exchange Electrolytes

Previous studies using rotational disk electrode (RDE) and in-situ H₂-pump set-ups have shown that the kinetics for the hydrogen oxidation and evolution reactions (HOR/HER) on carbon supported platinum (Pt/C) are on the order of 100x larger in acid than in base. However, no study has been carried out on the difference in i_o between liquid and solid polymer alkaline systems. In this study, the exchange current density (i_o), a parameter used to quantify the kinetics of the HOR/HER, was calculated for Pt/C interfaced with a number of hydroxide exchange membranes (HEMs) and ionomers using the Butler-Volmer equation and in-situ kinetic studies. Comparison of the exchange current densities in H₂-pump and RDE set-ups allows insight into how the HOR/HER kinetics differ in each system. Initial data with a commercial HEM and ionomer material show the i_o for Pt/C in a HEM fuel cell to be two times larger than the i_o measured with RDE, meaning the HEM materials that transport the hydroxide ions to the catalyst surface create a different type of alkaline environment than the liquid electrolyte transporting free hydroxide ions in RDE. Various HEM and respective ionomer materials are substituted into the in-situ H₂-pump to observe how different cationic side chains affect the alkaline environment in a HEM fuel cell.