Electrochemical impedance measurement and analysis of anodic concentration polarization for pressurized solid oxide fuel cells

This paper investigates experimentally and analytically the effect of pressurization on the anodic concentration polarization of a planar anode-supported full cell with flow distributors in both anode and cathode using a recently-established high-pressure dual-chamber SOFC test facility. In it the power generating characteristics and electrochemical impedance spectra of such single-cell are measured at constant flow rates (anode: 0.5 slpm H₂ + 0.4 slpm N₂; cathode: 0.9 slpm air) and at a fixed operating temperature (T = 800°C) but with five different pressures (p) varying incrementally from to 1 atm to 5 atm. Measurements show that the high frequency arcs of impedance spectra decrease rather weakly with increasing p, while the low frequency arcs with characteristic frequencies occurring at about 0.5 ∼ 1 Hz decrease strongly 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.