Synthesis of binary and ternary nanocomposites based on g-C3N4 as efficient Z-scheme photocatalysts for visible-light degradation of water contaminant

Several novel binary and ternary nanocomposites were synthesized based on g-C₃N₄, consisting of ZIF-8/OH-g-C₃N₄/La₂Sn₂O₇ with different ratios of OH-g-C₃N₄, pyrochlore La₂Sn₂O₇, and ZIF-8 materials. Moreover, photocatalytic degradation of Rhodamine B (RhB) aqueous solutions was done under visible light irradiation to examine photocatalytic characteristics of the resulting samples. All materials’ physicochemical characteristics were explored by diffuse reflectance spectra (DRS), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV–Vis) absorption, and emission photoluminescence (PL) spectra. The photocatalytic activities of ZIF-8, OH-g-C₃N₄, and La₂Sn₂O₇ pyrochlore as well as binary OH-g-C₃N₄/La₂Sn₂O₇ (5 %, 10 %, 15 %) materials were scrutinized in degradation process of RhB contaminant. It was established that the binary 10 %La₂Sn₂O₇/OH-g-C₃N₄ was the best sample with the highest photocatalytic activity. Therefore, ternary (10 %La₂Sn₂O₇/OH-g-C₃N₄)/ZIF-8 (5 %, 10 %, 15 %) photocatalysts were also tested for the RhB degradation. Among the ternary samples, the (10 %La₂Sn₂O₇/OH-g-C₃N₄)/10 % ZIF-8 was found to be the optimal photocatalyst, which degraded 97.1 % of RhB (10 ppm) at pH = 11 in 120 min. Furthermore, the optimal photocatalyst was applied for reusability and scavenger tests. Under optimal conditions (photocatalyst dose=0.10 g, pH = 11, RhB concentration=10 ppm), the photocatalyst exhibited a minor decline in degradation efficiency from 97.1 % to 80.5 % after five consecutive reactions. The optimal ternary photocatalyst illustrated a dual Z-scheme mechanism for the charge transfer processes. As a result, such photocatalyst is a potentially useful substance for use in industrial wastewater treatments.