Flexible, light-weight and air breathing proton-exchange membrane fuel cells (F-PEMFC) are promising electricity generators for various future applications like drones and small portable devices [1, 2]. However, compared with “classic” fuel cells, such devices have worse performance in terms of power density on the basis of membrane area (W/cm²). Furthermore, reproducible fabrication is a challenge; promising prototypes were hand-fabricated using expensive equipment. For commercial success, F-PEMFCs must improve in terms of performance and manufacturability. However, this requires a good understanding of the respective device details down to the basic level. For this work, a COMSOL Multiphysics simulation of a F-PEMFC prototype [3] is built. The simulation will be fed with accurate catalytic and physical parameters and used for an interactive process of (A) describing the F-PEMFC’s operating characteristics in detail, (B) finding approaches for performance optimization and (C) comparing experimental with simulation results. Therefore, polarization curves are created, and reactant and current generation distributions are examined. Although collection of accurate catalytic and physical parameters is ongoing, preliminary results with comparable data [4] showed that it is likely that the F-PEMFC design is limited by oxygen mass transport. Consequently, we will present results of various changes in device configuration which might enhance cell performance, for example, in the cathode’s catalyst layer morphology geometry.