Photocatalytic activity enhanced by synergistic effects of nano-silver and ZnSe quantum dots co-loaded with bulk g-C3N4 for Ceftriaxone sodium degradation in aquatic environment

Abstract

The development of novel semiconductor with highly efficient photocatalytic activity for completely degrading organic pollutants in the aquatic environment is a dominating goal of modern chemistry. Herein, a novel composite with excellent photocatalytic activity was firstly synthesized by loading small size of ZnSe quantum dot (QDs) and nano-Ag onto the surface of the bulk g-C3N4 (CN). The novel composite (ZnSe-Ag/CN) was used to degrade Ceftriaxone sodium in the aquatic environment at low concentrations under visible light irradiation, and the 7%-ZnSe-Ag/CN composite displayed superior photocatalytic activity, approximately 89.24% of Ceftriaxone sodium has been degraded under visible light irradiation for 90 min, which was approximately 10.14-folds, 2.72-folds, 2.09-folds and 1.39-folds higher than pure ZnSe QDs, CN, 7%-Ag/CN and 5%-ZnSe/CN sample, respectively. Based on the adsorption test, the UV–vis diffuse reflectance spectra (DRS), the N2 adsorption–desorption isotherm, the photoluminescence spectra, the transient photocurrent response and the electrochemical impedance spectroscopy (EIS) measurements, the enhanced photocatalytic activity of the ZnSe-Ag/CN composite could be attributed to the excellent adsorbability, expansion of the light-harvesting scope, as well as the efficient separation of photogenerated electron-hole pairs. Meanwhile, the ZnSe-Ag/CN composite could produce a large amount of the hydroxyl radicals (OH) during the photocatalytic degradation process. Furthermore, a possible pathway of Ceftriaxone sodium degradation was proposed according to the detailed analyses of the produced intermediates to better understand the reaction process. Therefore, this work offers a new strategy for designing novel photocatalyst with excellent photocatalytic activity to remediation of water contamination.