Solid oxide fuel cells (SOFCs) have advanced rapidly for the last decades. Since 8 mol% yttria-stabilized zirconia (8YSZ) has been considered the most conventional material for SOFC electrolyte, a number of studies have been focused on improving 8YSZ performance by changing dopants or adding a trace of metal oxide. In this study, the effect of a trace of CuO (100 ppm) on the performance of 8YSZ-based SOFCs is investigated. It is found that addition of a trace of CuO not only promotes a densification of the YSZ electrolyte by acting as a sintering aid but also increases the amount of the oxygen vacancy in the YSZ electrolyte. The ionic conductivities are about 0.0173 S cm −1 and 0.0196 S cm −1 in pristine and CuO (100 ppm)–YSZ electrolyte, respectively. The cell performance is about 0.5103 W cm −2 at 800 °C, which is about 1.5 times higher than the cell based on the pure YSZ electrolyte. The gadolinium-doped ceria (GDC)/8YSZ bilayer cell test also shows similar improvement to the single YSZ cell tests. Thus, the introduction of a trace of Cu (100 ppm) to the 8YSZ can be promising for a solid oxide fuel cell electrolyte.
