Effect of O2 Concentration and Voltage on Nitric Oxide Decomposition over (LaSr)MnO3–(Ce,Gd)O2−x Cathode of Solid Oxide Fuel Cell

Abstract

A solid oxide fuel cell (SOFC) unit is constructed with Ni–yttria-stabilized zirconia (YSZ) as the anode, YSZ as the electrolyte, and La0.8Sr0.2MnO3–Ce0.9Gd0.1O1.95 as the cathode. DeNOx tests are performed at 700 to 800°C. NO decomposition occurs over the cathode. The N2 and O2 produced as the cathode gases can be in molar balance with the decomposed NO. Increasing NOx concentration, adding NO2, and increasing O2 concentration can all increase the NO conversion; increasing NO conversion with increasing O2 concentration is beneficial for DeNOx of lean-burn exhausts. The amount of oxygen desorbed as the cathode gas (O2,gas) is much larger than that utilized for power generation; this is an effect of desorption enhancement; this effect can be utilized for SOFC-DeNOx with least or no consumption of the anode fuel. The O2,gas formation rate increases with increasing voltage and is larger at 700°C than at 750°C. With increasing voltage, the NO conversion at 700°C increases but those at 750 and 800°C decrease. When the NO conversion is the same, the consumption of the anode fuel is much less at 700°C than at 750°C. Higher operating voltage results in less fuel consumption.