Facile synthesis and enhanced visible-light photoactivity of DyVO4/g-C3N4I composite semiconductors

• DyVO4/g-C3N4I composites were prepared by a facile heating method.
• DyVO4/g-C3N4I showed a higher activity than g-C3N4, g-C3N4I or DyVO4.
• O2− and h+ played an important role in the degradation of methylene blue.
• The 6.3% DyVO4/g-C3N4I composite showed the highest photoactivity.

DyVO4/iodine modified graphitic carbon nitride (DyVO4/g-C3N4I) composite semiconductors with different weight percents of DyVO4 were successfully synthesized by a facile heating method, and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV–vis diffuse reflection spectroscopy (UV–vis DRS), photoluminescence (PL) and electron paramagnetic resonance (EPR) spectra, N2 adsorption–desorption analysis and photo-electrochemical measurement. The resulting DyVO4/g-C3N4I semiconductor with a suitable weight percents of 6.3% DyVO4 showed the highest visible-light photoactivity, and its degradation ratio for methylene blue was more than 1.8 time higher than that of DyVO4, g-C3N4 and g-C3N4I. The H2 evolution rate of 6.3% DyVO4/g-C3N4I was 10.6, 4.7 and 1.7 times higher than that of DyVO4, g-C3N4 and g-C3N4I, respectively, while still having excellent reusability and stability. The obviously enhanced photoactivity of 6.3% DyVO4/g-C3N4I is mainly ascribed to the fact that the proper DyVO4 modified g-C3N4I increase its specific surface area, decrease band-gap energy, enhance absorption in the 400–700 nm region and promote efficient separation of photo-generated carriers. The mechanism on the improvement of visible-light photoactivity is discussed.

Figure optionsDownload as PowerPoint slideOnce DyVO4 and g-C3N4I are integrated together, the band alignment between the two semiconductors can drive the migration of photo-generated electrons (e−) from g-C3N4I to DyVO4 by the conduction band offset between g-C3N4I and DyVO4, whereas the photo-induced holes (h+) are transferred from DyVO4 to g-C3N4I by the valence band offset. The redistribution of electrons on one side of the junction (DyVO4) and holes on the opposite side (g-C3N4I) can greatly reduce the recombination of electrons and holes.