PEM (Proton Exchange Membrane) fuel cell — Butler-Volmer kinetics, Nernst equation, activation/ohmic/concentration overpotentials, polarization curve, membrane conductivity (Nafion), GDL/catalyst layer design, water management, stack sizing (cell count, active area), balance-of-plant (humidifier, compressor, coolant), efficiency calculation, degradation mechanisms, and system integration (hydrogen vehicle/stationary).
