Waste biomass derived nitrogen-rich carbon dots augmented g-C3N4 photocatalyst for valorization of glycerol

Abstract

The nitrogen-rich carbon dots (CDs) were successfully synthesized by using soyabean de oiled cake as a biomass waste source. This study explored the effects of two green synthesis techniques viz. hydrothermal and microwave. The optimum synthesis temperature was 240 °C, and biomass concentration was 0.05 g/ml. The optimum residence time depended on the preparation method. The higher quantum yield was observed for CDs prepared by microwave method at 78.7% followed by 62.6% for CDs prepared by hydrothermal. CDs synthesized by hydrothermal and microwave method had band gap of 2.48 and 2.23 eV, while lifetimes were 5.97 and 4.62 ns, respectively. The CDs were utilized to modify g-C3N4 to create metal-free heterojunction photocatalysts for photo-oxidation of glycerol. The major product was observed to be glyceraldehyde with a yield of 15.2% and a selectivity of 48%. The catalysts were also effective for oxidation of other alcohols such as ethylene glycol.