Real-Time Continuous Monitoring of Fuel Cell Ionomer Degradation with Electrochemical Inline Micro Sensor Arrays

Abstract

Proton Exchange Membrane Fuel Cells (PEMFCs) are the preferred energy source for green transportation over CO2 emitting engines. In Nafion®-based PEMFCs, the radical attack causes polymer chain scission and irreversible reaction. It results in the global and local thinning of the ionomer, followed by producing fluorinated and sulfated degradation materials into reactant outlet streams. Synchronous fluorinated and sulfated degradation products will accumulate into reactant outlet streams. Radical attack diminishes the performance and stability of membrane electrode assembly (MEA). Chemical degradation will increase the flow rate of the relevant fluorinated degradation products. The concentrations are enhanced at elevated temperatures and lower humidity conditions. The byproduct fluoride and sulfate anion emission rates can be drawn as the signature of the PEMFC degradations. Electrochemical micro-sensors have been promising diagnostics tools due to low cost, small size, robustness, and their applications for continuous real-time monitoring. We have used fluoride emission as a sensing model. Highly fluoride-sensitive membranes (LaF3/CaF2) for inline microsensor arrays have been introduced as the sensing active layer. The functionalization of the working electrode varies the selectivity/sensitivity. High sensitivity sub 1 ppm has been achieved after optimizing the sensing layer deposited by spin-coating. In addition, advanced deep learning (DL) and long-short term memory (LSTM) algorithms will be used for the sensor-based predictive maintenance (PM) of PEMFCs. Even higher sensitivities sub 100 ppt and prediction accuracy for the end of life (EOL) can be achieved based on LSTM algorithms. The development of inline microsensor arrays gives a complementary approach to existing PEMFC characterization and diagnostics techniques. Figure 1