Fabrication of g-C3N4/Y-TiO2 Z-scheme heterojunction photocatalysts for enhanced photocatalytic activity

The g-C3N4/Y-TiO2 Z-scheme heterojunction photocatalysts were successfully synthesized. Powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used for characterization. The photocatalytic activity of the as-prepared samples was investigated via the degradation efficiency of rhodamine B (RhB) under visible-light irradiation, and 20 mg L−1 RhB was completely degraded in 90 min. The results showed that the photocatalytic degradation of RhB conformed to pseudo-first-order kinetic fitting, and the kinetic constants of g-C3N4/Y-TiO2 were 4.27 times higher than those of g-C3N4/TiO2 and 14.18 times higher than those of Y-TiO2, respectively. The enhanced photocatalytic activity of g-C3N4/Y-TiO2 was due to the formation of a Z-scheme heterojunction by Y at the g-C3N4/TiO2 interface. Formation of the Z-scheme heterojunction resulted in the suppression of photo-generated electron–hole pair recombination and the increase of their lifetimes, which was demonstrated by the transient photocurrent response, electrochemical impedance spectroscopy, and the time-resolved photoluminescence spectra. The superoxide radical and photo-generated holes played a dominant role in the photocatalytic degradation process of RhB by g-C3N4/Y-TiO2.