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Hydrogen peroxide decomposition over Ln<inf>1-x</inf>A<inf>x</inf>MnO<inf>3</inf> (Ln = La or Nd and A = K or Sr) perovskites

Abstract:

The following perovskites La1-xKxMnO3 (x = 0-0.15), La1-xSrxMnO3 (x = 0-0.3), Nd1-xSrxMnO3 (x = 0-0.4) and Nd1-xKxMnO3 (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 Ln1-xKxMnO3 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. © 2001 Elsevier Science B.V.