Performance of a PEM fuel cell cathode catalyst layer under oscillating potential and oxygen supply

[Display omitted] •A model for impedance of the cathode catalyst layer in PEM fuel cell is developed and solved.•The layer is operated under applied in—phase oscillations of the overpotential and oxygen concentration.•A small sub—layer in the catalyst layer forms, which is fully transparent to oxygen transport.•Due to this layer, the total system impedance is dramatically reduced. A model for impedance of a PEM fuel cell cathode catalyst layer under simultaneous application of potential and oxygen concentration harmonic perturbations is solved. The solution demonstrates strong lowering of the layer impedance under increase in the amplitude of oxygen concentration perturbation. Small in–phase oscillations of the overpotential and oxygen concentration lead to formation of a sub–layer with negligible oxygen transport loss. Working as an ideal non–polarizable electrode, this sub–layer dramatically reduces the system impedance.