Preparation and charge transfer properties of carbon nanotubes supported CdS/ZnO-NWs shell/core heterojunction

ZnO nanowires (ZnO-NWs), which were densely grown on multi-walled carbon nanotubes (MWCNTs) arrays, were coated with CdS by successive ionic layer adsorption and reaction. The attained CdS/ZnO-NWs/MWCNTs heterojunction was characterized by scanning and transmission electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy. Electrochemical properties of the CdS/ZnO-NWs/MWCNTs arrays were investigated by electrochemical impedance spectroscopy. The photoelectrochemical response of the CdS/ZnO-NWs/MWCNTs nanocomposite electrode was further studied by amperometry under sunlight irradiation. The CdS/ZnO-NWs/MWCNTs nanocomposite-yielded photocurrent is 2.5 times that of ZnO-NWs/MWCNTs, which is due to the good alignment of the energy bands of CdS and ZnO, thus facilitate the separation of photoinduced electron-hole pairs. In addition, the MWCNTs improve the active surface area and act as electron acceptors, thus promote the interfacial electron-transfer process from the ZnO-NWs to the MWCNTs. The heterojunction arrays of CdS/ZnO-NWs/MWCNTs provide potential applications in the fields of photocatalysis and photoelectrical devices.

Research highlights
► CdS/ZnO nanowires shell-core structure.
► Heterojunctions based on CdS, ZnO and MWCNTs.
► Efficient separation of photogenerated charge.
► High photocurrent.