Enhanced photocatalytic performance of CdZnS nanoparticles and attapulgite/carbon nitride composites by carbon quantum dots mediated facilitated charge separation/transfer: Cr(VI) reduction and H2O2 production

Abstract

In this work, CdZnS@carbon quantum dots/amino-modified attapulgite/carbon nitride (CdZnS@CQDs/M-ATP/PCN), function as Z-scheme heterojunction photocatalysts, have been successfully prepared by the hydrothermal method. CdZnS@CQDs-1/M-ATP/PCN-1 was optimized toward reduction of Cr(VI) and production of H2O2 under visible light, showing significantly improved photocatalytic performance. After coupling of M-ATP/PCN-1 with CdZnS and a moderate addition of CQDs, the synergistic formation of Z-scheme heterojunctions photocatalytic system effectively enhanced the photocatalytic properties of the composites. The results revealed that the CdZnS@CQDs/M-ATP/PCN catalysts contain rich active centers and suitable energy band structures, which enable them to produce more OH and O2−. Additionally, they also absorb visible light strongly and thus effectively improves the photocatalytic activity. Specifically, the reduction of Cr(VI) by CdZnS@CQDs-1/M-ATP/PCN-1 catalyst was achieved greater than 97.6 %, along with the production of 719.32 μmol·L−1 H2O2. Combining density functional theory (DFT) calculations, experimental test results and characterizations, we find that the excellent photocatalytic performance is attributed to the incorporation of CQDs and the formation of Z-scheme heterojunctions. We have developed a non-precious metal-based efficient Z-scheme photocatalytic system using simple hydrothermal synthesis method, which has a very high potential for energy production, environmentally sustainable remediation, and water purification.