Anode and cathode overpotentials under accelerated stress testing of a PEM electrolysis cell

An in-situ reference electrode was used under accelerated stress testing of a proton exchange membrane electrolysis cell. The reference electrode enabled the measurement of anodic and cathodic overpotentials. The accelerated stress test (dynamic load degradation) was conducted for over 1000 h, and it included half-cell measurements of the known anode and cathode potentials, repeated polarization curves, electron impedance spectroscopy and nano-scale imaging. The experiment had an average full-cell degradation rate of 77 μV/h. The anodic overpotential appears to be the main driver of the full-cell efficiency loss. The cathode EIS measurements indicate catalyst layer degradation despite minimal effect on the full-cell performance. The anodic EIS measurements yielded a resistance double that observed at the cathode. By simultaneously analyzing high frequency resistance, corrected half-cell polarization curves and half-cell EIS measurements, half-cell overpotentials can be attributed with greater confidence.