Hydrogen peroxide decomposition over Ln_1-xA_xMnO₃ (Ln = La or Nd and A = K or Sr) perovskites

The following perovskites La_1-xK_xMnO₃ (x = 0-0.15), La_1-xSr_xMnO₃ (x = 0-0.3), Nd_1-xSr_xMnO₃ (x = 0-0.4) and Nd_1-xK_xMnO₃ (x = 0-0.15) have been prepared by the freeze-drying method. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy spectra (XPS) analyses showed the presence of the single crystalline perovskite phases with an enrichment of the surface with potassium for the Ln_1-xK_xMnO₃ samples. δ-Oxygen non-stoichiometries of the perovskites were studied by chemical analyses, temperature programmed reduction (TPR) and oxygen desorption (TPD) experiments. The results obtained suggest that the catalytic H₂O₂ decomposition over these perovskites is not determined by the surface K, Ln and Mn concentration nor by the Mn⁴⁺/Mn³⁺ surface ratio. On the other hand, a good correlation between the catalytic H₂O₂ decomposition and the δ-oxygen non-stoichiometries was found, especially for La perovskites. A suprafacial mechanism where the oxygen vacancies participate in the H₂O₂ decomposition is suggested.