(490a) In-Situ PEFC Oxygen Sensing: An Ultra-Microelectrode Sensor with Oxygen Flux Interrupt Measurements

Oxygen transport losses continue to plague polymer electrolyte fuel cells (PEFCs). These losses are due to gas-phase oxygen diffusion through the diffusion medium (DM) and electrode, as well as the dissolution into and diffusion through the electrode’s ionomer binder. Direct measurements of the partial pressure of oxygen at the DM/electrode interface would help resolve the relative contributions of these losses. Here we present a new sensor and method enabling direct, in-situ measurements of oxygen partial pressure at the DM/electrode interface using an ultra-microelectrode sensor embedded in a thin-film polymer housing and a novel oxygen flux interruption measurement technique. The oxygen flux interrupt method resolves the competing effects of oxygen depletion and sensor hydration that confound partial pressure quantification with calibration curves. Using this method, an instantaneous calibration point is obtained with each measurement. Here, the level of oxygen depletion is determined and analyzed for various PEFC operating current densities and humidification levels.