Mitigating PEMFC Degradation during Start-Up: Locally Resolved Experimental Analysis and Transient Physical Modelling

This paper discusses the results of an experimental and modelling activity devoted to the analysis of start-up/shut-down of PEM fuel cells under operative conditions representative of automotive applications, when mitigation strategies are implemented. The focus is on air start-ups after long stops, when permeated air into the anode could not be avoided. A transient and physical 2D model was developed, incorporating the main electrochemical reactions and pseudo-capacitive contributions, calibrated on specific experiments and validated on local measurements of potential and current. Through the simulations, the impact of each phenomenon was separated in the complex dynamics of the process, elucidating the key role of platinum oxides. The experimental measurements comprise the local potentials, provided by through-plate Reference Hydrogen Electrodes, and the in-plane currents, measured among four regions of a segmented hardware. A systematic study of mitigation strategies based on stressors is presented, like: anode flow rate, oxygen dilution and temperature. Their effectiveness results from the ability in reducing either the process duration or the maximum potential. The model helps in interpreting the observed changes and to obtain trends of corroded carbon as a function of stressors; a controlling role is played by the anode flow velocity and the anodic oxygen concentration.