Comparing Two New Composite Photocatalysts, t‑LaVO4/g‑C3N4 and m‑LaVO4/g‑C3N4, for Their Structures and Performances

The objective of this research was to prepare, characterize, and evaluate two new composite photocatalysts: t-LaVO4/g-C3N4 and m-LaVO4/g-C3N4. The two catalysts were synthesized with m-LaVO4 or t-LaVO4 and g-C3N4, and characterized by various techniques including Brunauer–Emmett–Teller method (BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible-light (UV-vis) diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. The structure characterizations indicate that the two composites have similar phase composition. Both of them consist of LaVO4 and g-C3N4. Meanwhile, their photoabsorption performance is also similar. The photocatalytic test indicates that both m-LaVO4 and t-LaVO4 can effectively promote the photoactivity of g-C3N4, as demonstrated with the PL and photocurrent–time experiments, although the optimal concentrations of LaVO4 in the two catalysts are different. Both LaVO4/g-C3N4 and t-LaVO4/g-C3N4 are promising photocatalysts for degradation of RhB.