Pressurized solid oxide fuel cells: Measurements of impedance spectra and anodic concentration polarization

A high-pressure dual-chamber SOFC testing facility is established to measure AC impedance spectra of a planar anode-supported single-cell stack using flow distributors, with emphasis on the effect of pressurization to the anodic concentration polarization. Measurements show that the high frequency arcs of impedance spectra decrease rather weakly with increasing pressure (p), while the low frequency arcs with characteristic frequencies occurring at about 0.5 ~ 1 Hz decrease largely with increasing p. It is found that the ohmic resistance is independent of p, but the polarization resistance and the calculated anodic concentration overvoltage decrease noticeably with increasing p.