(304e) In-Situ Kinetic Studies of the Hydrogen Oxidation Reaction for Hydroxide Exchange Membrane Fuel Cells

In previous studies, the kinetics of the hydrogen oxidation reaction (HOR) and evolution reaction (HER) on carbon-supported platinum (Pt/C) have been measured for solid acid electrolytes in a hydrogen pump cell. This method eliminates the overlap of the kinetic and diffusion limiting currents seen in rotational disk electrode (RDE) data that prevents the calculation of the exchange current density (i_o) for platinum in liquid acid electrolytes. The slower kinetics in liquid base electrolytes allow i_o to be quantified but may not mirror the kinetics found in an alkaline polymer electrolyte fuel cell system. In this study, the HOR/HER activity was calculated for Pt/C catalysts interfaced with a hydroxide exchange membrane (HEM) using in-situ kinetic studies. Comparison of the exchange current densities in a H₂-pump and rotational disk electrode set-up allows insight into how the HOR/HER kinetics differ in each system. By fitting the linearized Butler-Volmer equation to the H₂-pump polarization curves, i_o was found to be two times larger than the i_o measured with RDE, meaning that the ionomer and HEM materials responsible for transporting the hydroxide ions to the catalyst surface create a different type of basic environment in a HEM fuel cell than the liquid electrolyte transporting free hydroxide ions in RDE.