Synthesis, band structure and photocatalytic properties of Sillén–Aurivillius oxychlorides BaBi5Ti3O14Cl, Ba2Bi5Ti4O17Cl and Ba3Bi5Ti5O20Cl with triple-, quadruple- and quintuple-perovskite layers

Abstract

Sillén–Aurivillius layered oxyhalides with single-, double- and triple-perovskite slabs (n = 1–3) are promising visible-light-driven photocatalysts for water splitting with different behaviors observed depending on n. However, there was no report on the photocatalytic activity of n ≥ 4 phases. Here, we report three new oxychlorides BaBi₅Ti₃O₁₄Cl, Ba₂Bi₅Ti₄O₁₇Cl and Ba₃Bi₅Ti₅O₂₀Cl, respectively, with triple-, quadruple- and quintuple-perovskite layers. The synthesis of these phases involves a “bricklaying” synthesis, where a plain perovskite, BaTiO₃, a Sillén phase, BaBiO₂Cl, and Aurivillius phases Bi₄Ti₃O₁₂, BaBi₄Ti₄O₁₅, and Ba₂Bi₄Ti₅O₁₈ were used as building blocks. The present Sillén–Aurivillius oxychlorides have appropriate valence and conduction band levels for visible-light-induced water splitting. DFT calculation for BaBi₅Ti₃O₁₄Cl (n = 3) and Ba₃Bi₅Ti₅O₂₀Cl (n = 5) indicates that their valence and conduction bands are separated spatially on the perovskite and fluorite layers, respectively. The photocatalytic activity of the three Sillén–Aurivillius oxychlorides is enhanced with increasing the number of the perovskite layers.