CdWO4 polymorphs: Selective preparation, electronic structures, and photocatalytic activities

This work explored the selective synthesis of polymorphs of CdWO4 in either tetragonal or monoclinic phase by optimizing the experimental parameters. Systematic characterization indicated that both polymorphs possessed similar spherical morphologies but different structural building blocks. Electronic structures calculations for both polymorphs demonstrated the same constructions of conduction band or valence band, while the conduction band widths of both polymorphs were quite different. Both CdWO4 polymorphs exhibited good photocatalytic activity for degradation of methyl orange under UV light irradiation. When comparing to some other well-known tungstate oxide materials, the photocatalytic activity was found to follow such a consequence, monoclinic CdWO4≈monoclinic ZnWO4>tetragonal CdWO4>tetragonal CaWO4. The specific photocatalytic activity of monoclinic CdWO4 was even higher than that of commercial TiO2 photocatalyst (Degussa P25). The increased activity from the tetragonal CdWO4 to the monoclinic was consistent with the trend of the decreased symmetry, and this could be explained in terms of the geometric structures and electronic structures for both polymorphs.

Monoclinic CdWO4 exhibited a much higher photocatalytic activity than the tetragonal form owing to the lower symmetry, more distorted geometric structure, and the dispersive band configuration.Figure optionsDownload as PowerPoint slideResearch highlights
► Polymorphs of CdWO4 in either tetragonal or monoclinic phase were selectively synthesized.
► Both polymorphs possessed similar spherical morphologies, while the relevant structural building blocks were different.
► Photocatalytic activities of CdWO4 polymorphs depended strongly on the symmetry, geometric structure, as well as band configuration.