New Dion-Jacobson Phase Three-Layer Perovskite CsBa₂Ta₃O₁₀ and Its Conversion to Nitrided Ba₂Ta₃O₁₀ Nanosheets via a Nitridation-Protonation-Intercalation-Exfoliation Route for Water Splitting

We report on the synthesis of new Dion-Jacobson phase three-layer perovskite CsBa₂Ta₃O₁₀ crystals by conventional solid-state reaction and fabrication of their nitrided Ba₂Ta₃O₁₀ nanosheets via a nitridation-protonation-intercalation-exfoliation route for visible-light-driven photocatalytic water splitting application. The two-dimensional crystal structure of CsBa₂Ta₃O₁₀ refined by the Rietveld refinement method belongs to the simple tetragonal system and consists of corner-shared distorted TaO₆ octahedra and Ba cations in cuboctahedral sites forming triple-layer perovskite slabs. The valence and conduction band edge potentials estimated by density functional theory with respect to vacuum scale and normal hydrogen electrode indicate that CsBa₂Ta₃O₁₀ is a UV-light-active semiconductor that can be used for photocatalytic water splitting and decomposition of organic pollutants. The projected electronic wave functions contour plot of CsBa₂Ta₃O₁₀ in the (1 0 0) plane exhibited two different Ta-O bonds. The nitridation at 800 °C for 5 h under NH₃ atmosphere was found to be suitable for retaining the phase-purity of nitrided CsBa₂Ta₃O₁₀ crystals. The fabricated nanosheets of nitrided Ba₂Ta₃O₁₀ with lateral sizes ranging from several hundred nanometers to a few micrometers and height of about 2.3 nm can be applied for visible-light-driven photocatalytic water splitting.