Datasets related to pubblication: Elena Colombo et al 2021 J. Electrochem. Soc. https://doi.org/10.1149/1945-7111/abf4eb 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...