Effect of O 2 concentration on performance of solid oxide fuel cells with V 2O 5 or Cu added (LaSr)(CoFe)O 3-(Ce,Gd)O 2- x cathode with and without NO

A solid oxide fuel cell unit is constructed with Ni-(Ce,Gd)O _{2- x} (GDC) as the anode, yttria-stabilized zirconia as the electrolyte, and V ₂O ₅ or Cu added (LaSr)(CoFe)O ₃-GDC as the cathode. The effect of the O ₂ concentration on the open circuit voltage (OCV) is studied and a mass-transfer limited OCV is observed. The power density with Cu addition can be much higher than that with V ₂O ₅ addition but the effect of the O ₂ concentration with Cu addition is larger than that with V ₂O ₅ addition. Without the presence of NO, both the power density and the OCV decrease with decreasing O ₂ concentration. The OCV variation can be substantial with the variation of the flow rate, the O ₂ concentration and the NO concentration. The presence of CO ₂ can increase the OCV while that of NO can decrease the OCV; however, a synergistic effect can occur on the OCV when NO is present at a very low O ₂ concentration which results in a sudden drop of the OCV.