Photocatalytic activity of CaTaO2N nanocrystals obtained from a hydrothermally synthesized oxide precursor

Abstract Highly crystalline CaTaO 2 N nanoparticles possessing large specific surface areas were investigated as photocatalysts for the decomposition of methyl orange. Two different Ca 2 Ta 2 O 7 precursors were synthesized by classical solid state synthesis and a hydrothermal soft-chemistry approach, respectively. In both cases, nitridation was carried out by thermal ammonolysis. The obtained CaTaO 2 N samples were compared with respect to their optical, thermal and morphological properties as well as their photocatalytic activities. In particular, the influence of ammonolysis temperature on the photocatalytic properties was studied. Using hydrothermally synthesized Ca 2 Ta 2 O 7 , phase pure CaTaO 2 N was obtained already at a relatively low ammonolysis temperature of 860 °C. Morphological investigations show that the CaTaO 2 N samples from the hydrothermally synthesized precursor consist of single-crystalline particles of 45–70 nm diameter with high specific surface areas between 12 and 19 m 2  g −1 , depending on ammonolysis temperature. A considerable photocatalytic activity for methyl orange degredation was found for the nanoscaled CaTaO 2 N particles prepared at lower ammonolysis temperatures. Using CoO x as co-catalyst, a further strong enhancement of the methyl orange decomposition by a factor 5–10 was achieved.