Ag promoted La0.8Ba0.2MnO3 type perovskite catalyst for N2O decomposition in the presence of O2, NO and H2O

La0.8Ba0.2MnO3 and silver promoted La0.8Ba0.2MnO3 type perovskite catalysts have been studied for N2O decomposition reaction. These catalysts were prepared by co-precipitation process followed by impregnation method for Ag incorporation. These catalysts were characterized in detail by means of ICP-OES, XRD, BET, SEM, STEM, EDX, XPS, O2-TPD and H2-TPR analysis. An appreciable increase in catalytic activity was achieved by promoting the lanthanum manganate by Ba as well as Ag. The promotional effect of Ag was observed maximum at 1 wt% optimized loading. The effect of O2, NO and H2O on the bare and Ag promoted catalysts for N2O decomposition was also investigated. The catalytic activity for N2O decomposition was significantly increased by Ba substitution as well as by Ag promotion. The activity of these improved catalysts was also relatively less affected in presence of oxygen, water vapour and NO, thereby showing promotional effect of silver on N2O decomposition. These catalysts were also prepared in supported forms using ceramic honeycomb via in situ co-precipitation method, and then tested for N2O decomposition reaction. Supported catalysts show equally good catalytic activity towards N2O decomposition. XPS and O2-TPD studies suggest that Ag incorporation results in increase of Mn4+/Mn3+ ratio of La0.8Ba0.2MnO3 catalyst. TPR studies also provided the clear evidence to this effect. This improved redox property of Ag promoted perovskite catalyst was correlated to its enhanced catalytic activity for N2O decomposition.

Graphical abstractCatalytic activity of LaMnO3 for N2O decomposition reaction has been improved by Ba substitution as well as Ag promotion, and it appears that Ag doping also alters the redox properties of perovskite structure, mainly in respect of Mn4+/Mn3+ ratio. This is the main cause of improved catalytic activity as substantiated by XPS, TPD and TPR analysis.Figure optionsDownload full-size imageDownload high-quality image (107 K)Download as PowerPoint slideHighlights► Catalytic activity of LaMnO3 has been improved by Ba and Ag promotion. ► Ag addition alters the redox properties of perovskite, which is responsible for improved catalytic activity. ► Altered valance states of Mn has been confirmed by XPS studies and corroborated by TPD as well as TPR analysis. ► 1 wt% Ag promoted La0.8Ba0.2MnO3 shows 100% N2O conversion at 550 °C with a reaction rate of 0.028 mmol g−1 min−1.