Synthesis of Au-Cu2S Core-Shell Nanocrystals and Their Photocatalytic and Electrocatalytic Activity

We synthesized stable Au-Cu2S core-shell-type hybrid nanocrystals, in which the spherical Au core encapsulates in the disk-type Cu2S nanocrystals (avg. size = 7 +/- 1 nm), using the simple in situ solvothermal growth of Cu2S on Au nanoparticle seeds. Binding energy and band gap measurement provides evidence for the electron withdrawal of the Au core from the Cu2S shell. The Au encapsulation enhances the visible-light-driven photocatalytic degradation yield of methylene blue and rhodamine B dyes. In contrast, it reduces the photocatalytic and electrocatalytic activity toward the degradation of 1,4-dioxane. The efficient interfacial electron transfer from the excited Cu2S to the Au enhances the oxidative degradation of the dyes. However, the electron withdrawal of the Au core would suppress the catalytic ability of Cu2S to generate the H2O2 intermediates, which decreases the degradation efficiency for 1,4-dioaxne.