BaTi sub(1-x)Cu sub(x)O sub(3) perovskites: The effect of copper content in the properties and in the NOx storage capacity

BaTi sub(1-x)Cu sub(x)O sub(3) perovskites have been prepared by the Pechini's sol-gel method and the effect of copper in the structural and physico-chemical properties of the perovskites and in the performance of the catalysts for NOx storage has been studied. XRD and Raman spectroscopy results indicate that all the copper containing catalysts present a distortion of the original tetragonal structure due to the incorporation of copper into the lattice. The XPS and H sub(2)-TPR results reveal that the copper catalysts, except for BaTiCu0,5 catalyst, present two copper species (with different electronic interaction with the perovskite) and active surface oxygen species. Additionally, it seems that the fraction of copper with a strong electronic interaction with the perovskite or incorporated into the perovskite structure increases with the copper content. The active sites created on the BaTi sub(1-x)Cu sub(x)O sub(3) perovskite surface bring to the catalysts activity for the NO to NO sub(2) oxidation and for the NOx adsorption. The NOx storage capacity increases with the copper content and reaches a limit for the BaTiCu2 catalyst (300 [mu]mol/g, at 420[degrees]C) which is within the range of the values reported for the noble metal-based catalysts.