S, N co-doped carbon quantum dots/TiO2 nanocomposite as highly efficient visible light photocatalyst.

In this paper, we report on the preparation of S, N co-doped carbon quantum dots (CQDs)/TiO2 nanocomposite using a hydrothermal process where S, N-CQDs were concurrently synthesized and anchored to the surface of the TiO2. The prepared nanocomposite was carefully characterized to identify the morphology and structure, crystallinity, chemical composition and optical properties. The photocatalytic activity of the nanocomposite was investigated for degradation of acid red 88 (AR88) under visible light irradiation. The capability of the S, N-CQDs/TiO2 nanocomposite to remove AR88 (77.29%) was higher than that of pure TiO2 (23.7%). In order to determine the influencing factors on the photocatalytic activity of the prepared nanocomposite, we studied various contents of the photocatalyst, the effect of pH and the content of H2O2. Further investigations were conducted to reveal the mechanism of photocatalytic degradation using radical scavenging agents. The stability and reusability of the S, N-CQDs/TiO2 photocatalyst was tested in four reaction cycles (870 min) which showed a 25% loss of photoactivity after the fourth photocatalytic reaction.