Synergistic enhancement of photocatalytic degradation of dyes by structural defects and silver nanoparticles

The AgNPs@NCN composite was prepared by loading silver nanoparticles (AgNPs) onto the surface of carbon nitride (g-C3N4) with nitrogen-vacancy and cyanide defect and used for the synergistic degradation of methylene blue (MB) by the structural defect of g-C3N4, the surface plasmon resonance of AgNPs and Schottky barrier formed between them. The morphology, structure, chemical composition and photoelectrochemical properties were characterized by SEM, TEM, FTIR, XRD, XPS, BET and UV–Vis. The effects of different loads of AgNPs on photocatalytic performance were investigated and the results showed 10%AgNPs@NCN exhibited good photodegradation performance. The maximum degradation efficiency of MB by 10%AgNPs@NCN reached 100% with the rate constant of 0.05443 min−1, which was 9.15 and 6.89 times higher than those of g-C3N4 (0.00595 min−1) and NCN (0.0079 min−1), respectively. The mineralization degree of organic pollutants was evaluated by total organic carbon (TOC) and the results showed that the TOC removals of 10%AgNPs@NCN photocatalytic reaction were 77% and 93% for MB and wastewater, respectively. After four cycles of photocatalytic degradation experiments, the degradation rate of MB was still more than 98.2% and there was no significant change in the characteristic stretching of the catalyst, indicating that the prepared photocatalyst had good stability and reusability.