Novel synthesis of siligraphene/tungstates (g-SiC/AWO) with promoted transportation of photogenerated charge carriers via direct Z-scheme heterojunctions.

We developed here the efficient photocatalysts for the removal of high concentrations of tetracycline under visible light by immobilizing the AWO (A = Ag, Bi, Na) nanocrystals on the surface of siligraphene (g-SiC) nanosheets. The g-SiC/AWO composites was synthesized by magnesiothermic synthesis of g-SiC and sonochemical immobilization of tungstates. These new heterojunctions of g-SiC/tungstates show superior photocatalytic activities in the degradation of high concentrations of tetracycline and 97, 98, and 94% of tetracycline were removed by using low amounts of g-SiC/Ag2WO4, g-SiC/Bi2WO6, and g-SiC/Na2WO4 catalysts, respectively. Based on band structures, the band gaps reduce and the photocatalytic activities were extremely enhanced due to the shortening of electron transfer distance through the Z-scheme mechanism. Also, the graphenic structure of g-SiC is another parameter that was effective in improving photocatalytic performance by increasing the electron transfer and decreasing the rate of electron-hole recombination. Furthermore, the π back-bonding of g-SiC with metal atoms increases the electron-hole separation to enhance the photocatalytic activity. Interestingly, g-SiC composites (g-SiC/AWO) showed much higher photocatalytic properties compared to graphene composites (gr/AWO) and can remove the tetracycline even at dark by producing the oxygenated radicals via adsorption of oxygen on the positive charge of Si atoms in siligraphene structure.

Novel siligraphene/g-C3N4 composites with enhanced visible light photocatalytic degradations of dyes and drugs.

In this research, a novel graphene-like SiC (siligraphene) was synthesized using a natural precursor and used to improve the photocatalytic activity of g-C3N4. The synthesized siligraphene has shown an excellent photocatalytic property due to its low band-gap and graphene-like structure which increases the electron transfer and reduces the electron-hole recombination rate and can improve the photocatalytic activity. Also, the positive charged Si atoms in siligraphene structure can adsorb oxygen to produce radicals that can promote the oxidation reaction. However, commercial ß-SiC has exhibited very poor photocatalytic properties. As we know, g-C3N4 is a potential material for photocatalytic applications. Here, the novel siligraphene/g-C3N4 composites were successfully synthesized to enhance the photocatalytic properties of g-C3N4 in the degradation of model dyes (Congo red, Methyl red, and Methyl orange) and model drugs (Acetaminophen and Tetracycline) under visible light irradiation. Results show that siligraphene/g-C3N4 composite exhibits much better photocatalytic properties than pure g-C3N4. This enhanced photocatalytic properties can be justified by the enlarged surface area, suitable band gap, excellent electron properties, appropriate surface charge, and efficient migration of electron in siligraphene/g-C3N4 composite.