Enhanced Photo-Fenton Catalytic Performance toward Acid Orange II by FeOCl/CdS Quantum Dot Composites: Density Functional Theory Calculations and Mechanistic Insights

FeOCl has attracted much attention for its good photo-Fenton properties. However, there are still some limitations to the removal efficiency of organic pollutants. Visible-light-responsive FeOCl/CdS quantum dot composites were prepared by calcination to overcome their flaws, and their catalytic activity was explored by the degradation of acid orange II (AO-II). The experimental results showed that the FeOCl/CdS composites exhibited better catalytic performance than pure components. The F₁Cd_0.5 composite (mass ratio of FeOCl to CdS is 1:0.5) achieved 98.5% removal efficiency of AO-II, which is 14.8 times higher than that of FeOCl+CdS under similar experimental conditions; moreover, the F₁Cd_0.5 composite still exhibits a high stability after five cycles. According to the characterization and experimental results with density functional theory calculations together, it is proposed that the type II carrier transfer-separation mechanism plays a leading role in enhancing the photodegradation performance of the photo-Fenton catalysts. This study provides a new idea to further improve the catalytic efficiency of the photo-Fenton technology for organic pollutant degradation.