Time Resolved Measurements of Proton Conductivity of Nafion: an Incentive for Theoretical Modelling

Electrochemical atomic force microscopy allows spatially resolved measurements of proton conductivity of proton exchange membranes on a nanoscale [1]. A potential step perturbation is applied to the electrochemical cell which consists of a platinum layer (typically acting as anode) on a commercially available Nafion 212 membrane and the platinum coated tip of the atomic force microscope in an environmental chamber. Depending on the gas composition, different electrochemical reactions can be investigated. In the case of using hydrogen the potential step leads to proton formation at the anode and backformation of hydrogen at the cathode. The dynamic information of the system is included in the response current and the related voltage-time signal. A Fourier Transformation converts the data to the frequency domain and the impedance can be calculated [2]. In principle, this technique provides the same information as electrochemical impedance spectroscopy, but due to the spatial resolution of a few nanometers a detailed view of proton conductivity within a proton exchange membrane is accessible. The results and their comparison with simulations may be used to develop a much more sophisticated model of a proton exchange membrane fuel cell