{Phase transformations during HLnTiO4 (Ln=La, Nd) thermolysis and photocatalytic activity of obtained compounds}

Abstract

Layered HLnTiO4 (Ln¼La, Nd) compounds belonging to Ruddlesden–Popper phases were found to form partially hydrated compounds Ln2Ti2O7 ? xH2O during thermal dehydration as well as defect oxides Ln2□Ti2O7 as final products. Further heating of metastable defect Ln2□Ti2O7 substances leads to the formation of pyrochlore-type oxides Ln2Ti2O7 (p), with subsequent transformation under higher tempera- tures to stable layered 110-type perovskites Ln2Ti2O7. The occurring structure transformations lead to an increase of photocatalytic activity in the order of HLnTiO4oLn2Ti2O7 ? yH2OoLn2□Ti2O7oLn2Ti2O7 (p)oLn2Ti2O7 in the reaction of hydrogen evolution from aqueous isopropanol solution.