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

• We studied dehydration and further thermolysis of HLnTiO4 (Ln=La, Nd) compounds.
• XRD, STA and solid state IR studies were carried out.
• A new series of metastable Ln2Ti2O7·yH2O compounds was obtained.
• We examined the photocatalytic activity of all obtained compounds. The hydrogen evolution rate increased in the course of the structure changes during thermolysis.

Layered HLnTiO4 (Ln=La, 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 temperatures to stable layered 110-type perovskites Ln2Ti2O7. The occurring structure transformations lead to an increase of photocatalytic activity in the order of HLnTiO4

Layered HLnTiO4 (Ln=La, Nd) compounds form partially hydrated Ln2Ti2O7·xH2O compounds during thermal dehydration, further heating results to the formation to defect oxides Ln2□Ti2O7, pyrochlor-type oxides Ln2Ti2O7 (p), with subsequent transformation to layered 110-type perovskites Ln2Ti2O7. Structure transformations lead to an increase of photocatalytic activity in the order of HLnTiO4