Photocatalytic Activity and Stability of Organically Modified Layered Perovskite-like Titanates HLnTiO 4 (Ln = La, Nd) in the Reaction of Hydrogen Evolution from Aqueous Methanol.

Two series of hybrid inorganic–organic materials, prepared via interlayer organic modification of protonated Ruddlesden–Popper phases HLnTiO₄ (Ln = La, Nd) with n-alkylamines and n-alkoxy groups of various lengths, have been systematically studied with respect to photocatalytic hydrogen evolution from aqueous methanol under near-ultraviolet irradiation for the first time. Photocatalytic measurements were organized in such a way as to control a wide range of parameters, including the hydrogen generation rate, quantum efficiency of the reaction, potential dark activity of the sample, its actual volume concentration in the suspension, pH of the medium and stability of the photocatalytic material under the operating conditions. The insertion of the organic modifiers into the interlayer space of the titanates allowed obtaining new, more efficient photocatalytic materials, being up to 68 and 29 times superior in the activity in comparison with the initial unmodified compounds HLnTiO₄ and a reference photocatalyst TiO₂ P25 Degussa, respectively. The hydrogen evolution rate over the samples correlates with the extent of their interlayer hydration, as in the case of the inorganic–organic derivatives of other layered perovskites reported earlier. However, the HLnTiO₄-based samples demonstrate increased stability with regard to the photodegradation of the interlayer organic components as compared with related H₂Ln₂Ti₃O₁₀-based hybrid materials. [ABSTRACT FROM AUTHOR]