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The monoclinic BiVO4 in a powder state was prepared via a hydrothermal method, with the addition of KCl as a structure-directing agent. The as-prepared sample was calcined at different temperatures (400–600 °C), either in the air or in Ar gas. It is found that, though the morphology and crystal structure mostly remain unchanged, the bandgap properties are modified during calcination. A detailed analysis of the surface chemical states and optical absorption properties reveals the involvement of tetravalent vanadium ions and oxygen vacancies as the cause of the band modification. The bandgap properties are to be found tunable via changing the calcination condition, as well as the KCl concentration in the precursor. The photocatalytic properties of BiVO4 samples are greatly enhanced with the addition of KCl in the precursor, but degraded by post-annealing, where the residual Cl in the calcined sample may act as an inhibitor. The enhanced photoactivity is explained in terms of favorable faceting, bandgap modification, and heterojunction of BiVO4/BiOCl.

The interphase properties in nanocomposites indicate the interaction between filler and matrix, which is dependent on the preparation method, shape, and size of filler and the chemical interaction between two phases. Local chemical environment in polymer matrix give rise to the different dielectric properties compared to that of bulk material. These properties allow the understanding of their effects on the dielectric properties and glass transition (T-g) of the nanocomposites. In this study, interphase power law model was used to predict the interphase properties based on the experimental dielectric constant of polyimide (PI) with BaTiO3, TiO2, and ZrO2 nanocomposites. They were prepared via in situ polymerization of PI whose dielectric constant were increased at interphase filler volume fraction of BaTiO3, TiO2, and ZrO2 at 3.8, 2.05, and 1.7, respectively. These results indicate that PI/ceramics nanocomposites had poor dispersion and weak interphase interaction between the filler and the matrix, as an evidence of scanning electron microscopy and Fourier transform infrared spectroscopy results. However, PI incorporated with high aspect ratio of BaTiO3 nanofiber shows better dispersion than nanocomposites of TiO2 and ZrO2 filled PI; therefore provide higher dielectric constant and T-g. Funding Agencies|AUN/SEED-Net [6050315]; RU (I) [814242]

The monoclinic BiVO4 was synthesized via a facile one-pot hydrothermal synthesis. KCl concentration in the precursor greatly influences the crystal growth, morphology, and absorption properties of BiVO4 attributed to the effect of Clˉ ions on the formation of BiOCl intermediate and preferential growth of BiVO4 crystals along {010} planes. The photocatalytic property of BiVO4 is accordingly altered based on the KCl content. The “shuriken-like” BiVO4 prepared with 3 ​mmol of KCl exhibits the highest photocatalytic activity among our samples. Its photocatalytic rhodamine B degradation efficiency could reach 94.7% after 4 ​h of visible-light irradiation. The degradation efficiency only decreased to 90.8% after four runs of 4 h irradiation. The photodegradation rate with the shuriken-like BiVO4 is around 2.3 times higher than that with the rod-like BiVO4 prepared without KCl, owing to its highest relative intensity ratio of (040) to ( 1 ¯ 21 ) plane, which maximizes the exposed active {010} facets of BiVO4.

Heterojunction photocatalysts have attracted a significant amount of attention due to their advantages over a single photocatalyst and, particularly, their superior spatial charge separation. Herein, the BiVO4/Bi2S3/SnS2 heterojunction was synthesized via solvothermal synthesis with different ratios of BiVO4 to SnS2. The photodegradation rate of the 0.03 BiVO4/SnS2 sample for rhodamine B removal is 2.3 times or 2.9 times greater than that of a single SnS2 or BiVO4, respectively. The chemical bond between photocatalysts is confirmed by X-ray photoelectron spectroscopy (XPS), and the synchronized shift observed in binding energies strongly indicates the electron screening effect at the heterojunction. A Z-scheme model is proposed to explain charge transfer pathway in the system, in which the formation of Bi2S3 plays a crucial role in the enhanced photocatalytic performance of the heterojunction.