Enhancing photodegradation activity of g-C3N4 via decorating with S-doped carbon nitride quantum dots by in situ polymerization

In this work, sulfur doped carbon nitride quantum dots (S-CNQDs) were prepared by one-pot copolymerization using melamine and thiourea as starting materials. The composite (g-C3N4/S-CNQDs), showing enlarged surface area, was fabricated by one-step in situ polymerization. The composites displayed much better photocatalytic activity than pristine g-C3N4 in degradation of methyl orange (MO) under UV-visible light irradiation. The removal efficiency of MO reached by 94.3% under visible light (lambda > 420 nm) illumination within 80 min, whereas it was nearly 100% under UV-visible light (lambda > 350 nm) irradiation within 40 min. The enhanced photocatalytic activity of composites is attributed to the doping of S-CNQDs, which leads to higher separation of photo-generated electron-holes, extended visible light response and more active sites. Additionally, the potential mechanism of photocatalytic degradation on MO by g-C3N4/S-CNQDs was proposed. This work presented a simple way for constructing S-CNQDs-based g-C(3)N(4 )catalyst.