High Power Density, Low Temperature, Solid Oxide Fuel Cells at Elevated Oxygen Partial Pressure

ABSTRACT Lowering solid oxide fuel cell (SOFC) operating temperature has long been a goal due to greater interconnect, seal, and BOP material selection options, thus, lower cost, and potential for shorter startup/shutdown times and reduced degradation rates. However, high ohmic resistance from ion transport and sluggish oxygen reduction reaction (ORR) kinetics typically limit cell performance at lower temperatures (≤ 650°C). The high conductivities of ceria‐based electrolytes provide a path to lower operating temperature, but partial reduction (Ce ⁴⁺ Ce ³⁺ ) introduces electronic conductivity, reducing the cell's Faradaic efficiency (FE). Here, we evaluate the effect of cathode oxygen partial pressure () up to 1 atm and show higher suppresses electronic leakage, thus increasing open circuit potential (OCP) and FE—indicating that pressurization of ceria‐based SOFCs is a practical route to improving their FE. In addition, the elevated improves ORR kinetics, thus reducing electrode area specific resistance (ASR). The effect of in OCP and ASR is demonstrated on both Sr _0.5 Sm _0.5 CoO _3‐δ ‐Gd _0.1 Ce _0.9 O _2‐δ (SSC‐GDC) composite cathodes and our recently developed nano‐PSC infiltrated GDC cathodes, the latter resulting in the highest performing low temperature SOFC ever reported: 4.01 W·cm ⁻² at only 650°C.