Advanced characterization of polymer electrolyte fuel cells using a two-phase time-dependent model

Abstract

For polymer electrolyte fuel cells (PEFC) to become competitive, their operation in transport applications requires optimized performance, durability and costs. An indispensable component of this optimization is a detailed time-dependent characterization of PEFCs. For this purpose, several dynamic single-cell PEFC numerical models have been developed in the last 15 years. Here we present a new modeling approach with an advanced material parameterization of all governing time-dependent processes. This new modeling approach is based on the 1-D steady-state two-phase, five-layer PEFC model with a comprehensive material parametrization [1]. We further developed this approach by including the time-dependency of electron, proton, heat, dissolved water, gas and liquid water transport. Implementation in COMSOL allows for accurate spatio-temporal resolution and flexible model setups. We develop an improved electrochemical spectroscopy method by applying a sinusoidal perturbation of varying amplitude to the cell voltage. In contrast to (small-signal) electrical impedance spectroscopy, our model numerically solves for the nonlinear time-dependent response of the fuel cell, which enables us to retrieve information from large signals. We compute the response spectra at different operating points not only for electrical current density but also for dissolved water, liquid water, temperature and gas concentration and their gradients. These nonlinear response spectra serve for the development of improved model-based characterization techniques and fuel cell diagnostics. Acknowledgements: Financial support from the Swiss Federal Office of Energy (SFOE contract number: SI/501764-01) is gratefully acknowledged