Measurement of Through-Plane Humidity Distribution inside an MEA by Thin Film Sensor

Abstract

Measuring local humidity inside a proton exchange membrane fuel cell is essential for proper water management because water condition is closely related to the cell performance. Thin film humidity sensors (TFHSs) were fabricated by the micro-electromechanical system techniques for measuring local humidity inside a membrane electrode assembly. The width of the TFHS was only 100 µm and total thickness was 7 µm, which is thinner than the thickness of a catalyst layer (CL). The sensor was placed between the CL and the micro porous layer. Both of the anode and cathode side measurement were conducted. There was no significant performance reduction owing to the insertion of the TFHS. The humidity difference between the anode and the cathode CL surfaces in the high humidity supply gas condition was smaller than in the low humidity condition owing to the higher water diffusion coefficient of the PEM.