The “Apparent” Diffusion Coefficient of Electrons Through a Nafion Membrane

The hydrogen/oxygen fuel cell is a greener, more efficient energy solution. However, there are many problems with the fuel cell including storage, infrastructure, cost, the oxygen reduction reaction, and the durability of the proton exchange membrane (PEM). The PEM is not only used as the electrolyte for the cell but also as a physical barrier between the anode and the cathode. The integrity of this membrane is crucial to the functioning of the fuel cell. This thesis will examine using ferricyanide as a probe molecule for diagnostic experiment of Nafion membrane integrity. Using hydrodynamic voltammetry with a rotating disk electrode (RDE), the signals between a bare electrode surface and one modified with a Nafion membrane can be differentiated to observe if there are any discrepancies in the membrane coverage of the electrode. During this work, ferricyanide was observed to incorporate into the membrane during a hydration period in the solution. Different mechanisms of how this incorporated concentration affects the current response are discussed, concluding electron-hopping is the most plausible mechanism for the case at hand. The Tedford Equation was formulated model the hydrodynamic current response in the membrane taking into account rotation rate dependence and the apparent diffusion of electrons through the membrane