In this study, a series of calcium bismuthate samples having a different composition and type of crystal lattice was obtained. The diffuse reflectance spectroscopy found that both factors impact the calcium bismuthate ability to absorb the visible light irradiation. It was shown that the bandgap of synthesized photocatalysts depends on the degree of lattice defects. The catalytic activity of photocatalysts was studied in terms of decomposition rate of methylene blue by visible light in the presence of various samples of calcium bismuthate. It was found that the catalytic activity of calcium bismuthates with orthorhombic crystal lattice is lower than that of similar samples of rhombohedral lattice. Thus, samples with the lowest number of cation sublattice defects have the greatest catalytic activity.
The study describes use of pyrolytic synthesis method for preparation of visible light calcium bismuthate based photocatalyst. The advantage of the proposed method is that it allows obtaining single-phase, homogeneous samples with various types of crystal lattice and controlled defects. It is shown that it is possible to obtain crystalline calcium bismuthate with the same stoichiometry in the entire region of existence of the solid solution. Synthesized samples of calcium bismuthate have been characterized using the scanning electron microscopy and X-ray analysis. It was found that the scope and conditions of synthesis affect the degree of imperfection of both anionic and cationic sublattice of calcium bismuthate.