Reduction of nitrogen oxide by steam electrolysis cell using a protonic conductor SrZr0.9Yb0.1O3−α and the catalyst Sr/Al2O3

A steam electrolysis cell was constructed with a high-temperature type protonic conductor, SrZr0.9Yb0.1O3−α. The reduction of nitrogen oxide (NO) by hydrogen, which was produced by a steam electrolysis cell, was examined. Helium gas with 8% O2 and 1000 ppm NO was used as a model gas for the exhaust gas from automotive engines operating under lean-burn condition. The removal efficiency of NO was measured, using steam electrolysis cells with different catalysts on the cathodes. A mixture of Pt-sponge and Sr/Al2O3 catalyst was found to be most effective for the preferred reduction of NO in the presence of excess O2. It was suggested that the preferred reduction of NO occurred via the electrochemical reduction of NO absorbed into Sr/Al2O3, not via the chemical reduction of NO by H2 gas.