Electrochemical testing of composite electrodes of (La_1−xSr_x)_sMnO₃ and doped ceria in NO-containing atmosphere

The possibility of using electrochemical cells for removal of NO x from an exhaust gas with excess O2 has been examined. (La1−x Sr x ) s MnO3 (LSM) and ceria doped with Pr or Gd were selected as electrode materials and investigated in three-electrode cells. The electrodes were characterised electrochemically with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), and the gas composition monitored while the electrodes were polarised. The electrodes of (La0.5Sr0.5)0.99MnO3 (LSM50) and Ce0.8Pr0.2O2−δ exhibit higher current densities in 0.1% NO in Ar than in air at 300 to 400 °C during CV. This indicates some apparent selectivity towards NO compared to O2. The electrodes can remove NO, when polarised to at least −0.6 V vs. Pt/Air at 600 °C, and EIS measurements under polarisation indicate that the kinetics of the electrodes change, when the electrode potential gets below −0.6 V vs. Pt/Air.