Fabrication and evaluation of Au–Pd core-shell nanocomposites for dechlorination of diclofenac in water

Abstract

Nanocomposites with core-shell structure usually exhibit excellent catalytic properties due to unique interfaces and synergistic effect among composites. In this study, Au–Pd bimetallic nanoparticles (NPs) with core-shell structure (Au–Pd cs) by using Au NPs as core and Pd as shell were successfully fabricated and, for the first time, were used to investigate the dechlorination of diclofenac (DCF) at H2 atmosphere in water at room temperature. The degradation products were studied as well by using HPLC/Q-ToF MS/MS. The operational factors such as pH and composition of the Au–Pd cs were also studied. The results showed that nearly 100% of DCF (30 mg L−1, 50 mL, pH = 7) was dechlorinated in 4.5 h by 10 mL of 56 mg L−1 of Au–Pd cs. Ninety per cent of DCF was degraded in 6.5 h by the mixture of Au and Pd NPs. However, the individual Au NPs had no obvious effect in degrading DCF and the monometallic Pd NPs with comparable concentration only degraded less than 20% of DCF. Furthermore, the reaction mechanism of this catalytic process was studied in detail. It was found that the degradation was a second-order exponential reaction. The two main degradation products were obtained by cleaving the carbon–halogen bond of DCF and this made the degradation products more environmentally friendly.