Comparison of Electrochemical Impedance Measurements between Pressurized Anode-Supported and Electrolyte-Supported Planar Solid Oxide Fuel Cells

Abstract

Pressurization influence on electrochemical impedance spectra (EIS) of both anode-supported and electrolyte-supported cells (ASC and ESC) are measured and compared using a high-pressure SOFC facility. In it both ASC and ESC apply the same single-cell setup, a planar full cell having 40 × 40 mm2 effective reactive area sandwiched by a pair of rib-channel flow distributors (interconnectors) on both anode and cathode, using the same flow rates (Qanode = 0.5 slpm H2 + 0.4 slpm N2 and Qcathode = 0.9 slpm air) at 850°C, with five different pressures (1 ∼ 5 atm). It is found that ASC is more sensitive to pressurization than ESC, of which power densities of ASC/ESC at 0.7 V increase from 309/193 mW cm−2 to 476/250 mW cm−2, as p increases from 1 atm to 5 atm, corresponding to a 54%/30% increase. This result is explained by EIS measured data, in which both ohmic and polarization resistances of ASC are smaller than that of ESC. Moreover, the ohmic resistance is independent of pressurization for both ASC and ESC, remaining constant regardless of either unloaded or loaded conditions, while the polarization resistance decreases noticeably with increasing pressure for both ASC and ESC.