Acid protonation promoted different crystal phase structure silicon carbide-based carbon nitride composites to enhance the photocatalytic degradation of dye wastewater.

Acid-protonated crystalline silicon carbide-supported carbon nitride photocatalytic composites were successfully prepared by the impregnation-heat treatment method (P-g-C3N4/ß-SiC and P-g-C3N4/α-SiC). The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), UV-vis diffuse reflectance spectra (UV-vis-DRS) photoluminescence (PL), etc. The results of SEM showed that the P-g-C3N4/ß-SiC and P-g-C3N4/α-SiC materials were transformed from large-area lamellar structures to uniform and dispersed lamellar particles. The UV-vis-DRS and PL showed that the recombination probability of photogenerated electron-hole pairs of P-g-C3N4/ß-SiC and P-g-C3N4/α-SiC samples decreased and the band gap increased. The results of photocatalytic degradation of alizarin red S (ARS), acid fuchsin (AF), and basic fuchsin (BF) showed that the samples P-g-C3N4/ß-SiC and P-g-C3N4/α-SiC had excellent photocatalytic degradation performance. It is worth noting that the degradation performance of the sample P-g-C3N4/ß-SiC on the three dyes is better than that of P-g-C3N4/α-SiC. The electron spin resonance spectra (ESR) results showed that the ˙O2- and ˙OH produced by the two catalysts during the dye degradation process played a leading role in the degradation reaction. Fortunately, the catalyst maintains an excellent cycle life and can be reused more than seven times while degrading all three dyes.