Development of a measurement technique for current-density in PEFC using planar surface coil as a NMR signal detector (1st report, one-dimensional measurement of current-density generating in PEFC)

In a polymer electrolyte fuel cell (PEFC), current density through polymer electrolyte membrane (PEM) would be distributed along the electrode on membrane electrode assembly (MEA). To increase the electric power density of a PEFC, it is needed to find out some low-current density areas where electric power generation decrease due to a lack of hydrogen, flooding and so on. Therefore. a monitoring method of local current density in PEFC is required to achieve higher current density operation of a PEFC. We developed the new method to estimate the spatial distribution of current flowing through MEA in a PEFC using Nuclear-Magnetic Resonance (NMR) signal detector. The magnetic field strength induced by the current through MEA generating electric power is acquired as the frequency shift of the NMR signal by NMR signal detector. The one dimensional spatial distribution of frequency shift changing along the MEA was measured. In order to verify the method, under the assumption that the current through MEA was uniform, magnetic field strength induced by the current through GDL in a IEFC was analyzed theoretically. And then, the frequency shift at the each NMR signal detector was calculated as functions of the geometry of GDL, current and the position of the NMR signal detector. In these studies, the experimental results agree with the theoretical results.