The cross-substitution effect of tantalum on the photocatalytic water oxidation activity of BaNbO2N crystals grown by a flux method was investigated.

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We report on the synthesis of new Dion−Jacobson phase threelayer perovskite CsBa 2 Ta 3 O 10 crystals by conventional solid-state reaction and fabrication of their nitrided Ba 2 Ta 3 O 10 nanosheets via a nitridation−protonation− intercalation−exfoliation route for visible-light-driven photocatalytic water splitting application. The two-dimensional crystal structure of CsBa 2 Ta 3 O 10 refined by the Rietveld refinement method belongs to the simple tetragonal system and consists of corner-shared distorted TaO 6 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 CsBa 2 Ta 3 O 10 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 CsBa 2 Ta 3 O 10 in the (1 0 0) plane exhibited two different Ta−O bonds. The nitridation at 800 °C for 5 h under NH 3 atmosphere was found to be suitable for retaining the phase-purity of nitrided CsBa 2 Ta 3 O 10 crystals. The fabricated nanosheets of nitrided Ba 2 Ta 3 O 10 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.