Enhancement of NOx removal performance for (La0.85Sr0.15)0.99MnO3/Ce0.9Gd0.1O1.95 electrochemical cells by NOx storage/reduction adsorption layers

This study investigated the effect of adding a NOx adsorption layer to the cathode of an electrochemical cell on the removal of NOx from gaseous mixtures. The cathode was a composite of (La0.85Sr0.15)0.99MnO3 (LSM15) and Ce0.9Gd0.1O1.95 (CGO10). Two different kinds of adsorption layers, K–Pt–Al2O3 layer and Ba–Pt–Al2O3 layer (known as NOx storage/reduction (NSR) catalyst), were studied. The effects of the NSR adsorption layers on the electrode processes were characterized by electrochemical impedance spectroscopy (EIS). Both adsorption layers increased the reduction of NOx to N2 in an atmosphere that contained only NO. When O2 was present with NO in the atmosphere, the K–Pt–Al2O3 adsorption layer significantly enhanced the conversion of NOx to N2, but the Ba–Pt–Al2O3 adsorption layer had no effect. The selective removal of NOx under O2-rich conditions was achieved by modifying the LSM15/CGO10 cell with a suitable NSR adsorption layer. The improvement for NOx reduction by the adsorption layers was mainly contributed by the promotion of the adsorption and surface diffusion of NOx species at/near the triple phase boundary (TPB) regions of the electrode and probably the formation of a short and effective reaction path for NOx reduction. A stronger capability for oxidizing NO and/or trapping NOx under the test conditions may have contributed to the superior performance of the K–Pt–Al2O3 adsorption layer relative to the Ba–Pt–Al2O3 layer.