Strongly coupled CdX (XS, Se and Te) quantum dots/TiO2 nanocomposites for photocatalytic degradation of benzene under visible light irradiation

In this paper, a series of chalcogenide components CdX (XS, Se and Te) quantum dots/TiO2 binary hybrids were investigated by exploiting visible-light-driven organic compound degradation. CdX QDs were well dispersed on the surface of TiO2 nanoparticles with a firm and close contact based on the analysis of SEM, TEM, XRD and XPS. As results, the photocatalytic degradation performance of benzene from the most to the least is 95%, 90%, 86% for CdS-TiO2, CdSe-TiO2, CdTe-TiO2, respectively. The degradation rate was gradually decreased owing to two factors, on the one hand, the more positive valence band edge position of CdS (compared to CdSe and CdTe) and consequently the higher oxidation power of the photo-generated holes. On the other hand, the minimum band gap energy of CdS-TiO2 (compared to CdSe-TiO2 and CdTe-TiO2) in the photocatalytic degradation. The reaction intermediates and detailed reaction mechanism for the degradation of benzene were proposed. The analyses of the reaction intermediates showed that eight intermediates were formed during the photocatalysis decomposition process. OH and h+ were the dominant active species in the photocatalysis degradation of benzene over CdX-TiO2. Thus, CdX-TiO2 nanocomposites were shown to be efficient photocatalysts for environmental remediation.