Synergistically enhanced photocatalysis from plasmonics and a co-catalyst in Au@ZnO–Pd ternary core–shell nanostructures

Abstract

In this work, a new design of ternary core–shell nanostructures of Au@ZnO–Pd was demonstrated to realize the synergetic utilization of a plasmonic effect and an electron-trapping co-catalyst for enhanced photocatalytic performance. In the ternary hybrid nanostructures, ZnO provides photo-generated carriers with higher redox ability, under UV-visible light, and Au nanocrystals perform the plasmonic hot electron injection as well as the local electromagnetic field enhancement of ZnO photoexcitation. Meanwhile, the Pd NPs can efficiently trap the generated electrons to govern the directional separation of the charge carriers. The efficient charge carrier separation in the ternary hybrid nanostructures was confirmed by steady-state PL spectra, time-resolved PL decay spectra, and transient photocurrent responses. The photocatalytic activity of the Au@ZnO–Pd nanostructures was evaluated by photodegrading phenol and methylene blue, respectively, under simulated sunlight (λ = 360–780 nm), and the results showed that the Au@ZnO–Pd nanostructures gained a great enhancement of photocatalysis compared with ZnO, ZnO–Pd and Au@ZnO. Moreover, the effect of Pd loading content in the Au@ZnO–Pd nanostructures on the photocatalytic efficiency was studied within a certain range, indicating that the Au@ZnO–Pd photocatalyst with ∼1.8 wt% Pd loading exhibited the best photocatalytic activities for photodegrading both phenol and methylene blue. The generation and effect of active species in the photocatalytic process were investigated using ESR testing and radical scavenging experiments. As a consequence, the integration of the ternary Au@ZnO–Pd core–shell nanostructures could achieve collective effects to greatly increase the photocatalytic efficiency.