Shinya Morishita

Reduction of nitrogen oxide by a steam electrolysis cell using a proton conducting electrolyte

Abstract Removal of nitrogen oxide (NO) by electrochemical reduction was studied using a steam electrolysis cell with platinum electrodes and a proton conductor SrZr0.9Yb0.1O3 − α as the electrolyte. Without NO, the cell produced H2 with nearly 100% current efficiency in the temperature range 380–590 °C. With NO fed to the cathode, NO was effectively reduced. The main products were N2O and N2 at low current densities, and N2 and NH3 at higher current densities. When O2 was mixed into the cathode gas, NO was not reduced on the pure Pt cathode. However, ‘ Pt sponge + Sr Al 2 O 3 ’ catalyst on the Pt cathode showed a good catalytic ability for the reduction of NO supplied with O2.

Stability of SrZr0.9Yb0.1O3−α protonic conductor in atmosphere containing nitrogen oxides (NOx)

The stability of the SrZr0.9Yb0.1O3−α protonic conductor in an atmosphere containing nitrogen oxides (NOx) was investigated. When a fine powder of SrZr0.9Yb0.1O3−α with a specific surface area of about 50 m2/g was annealed at 440 °C in He gas containing 8% O2 and 0.1% NO, the formation of Sr(NO3)2 was observed by IR measurement, ion-chromatography analysis and ICP analysis. The formation mechanism of Sr(NO3)2 was examined by considering the thermodynamic equilibrium. Based on the results of the thermodynamic calculation, H2O dissolved into SrZr0.9Yb0.1O3−α was estimated to play an important role in the reaction for the formation of Sr(NO3)2 between SrZr0.9Yb0.1O3−α and NOx.