Photoelectrochemical Study on Charge Transfer Properties of ZnO Nanowires Promoted by Carbon Nanotubes

ZnO nanowires (ZnO-NWs) were adhesively grown on multiwalled carbon nanotubes (MWCNTs) arrays by a hydrothermal process. Electrochemical properties of the electrode based on the ZnO-NWs/MWCNTs nanocomposite were investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The photoelectrochemical responses of the ZnO-NWs/MWCNTs nanocomposite electrode were further studied by linear sweep voltammetry and amperometry under sunlight or UV light irradiation. Compared with pure ZnO-NWs on tantalum substrate, the charge transfer rate of the ZnO-NWs/MWCNTs nanocomposite was remarkably increased because of the MWCNTs. A Mott−Schottky plot displayed a high donor density of 3.9 × 10 19 cm −3, a flat band potential of −0.8 V, and a space charge layer of 7 nm. In addition, the ZnO-NWs/MWCNTs nanocomposite yielded higher photocurrent than pure ZnO-NWs. The decay constant of the ZnO-NWs/MWCNTs nanocomposite was also lower than that of its pure counterpart. The recombination of photoinduced electron−hole pairs in the ZnO-NWs/MWCNTs heterojunction was hindered, thus enhancing the photoelectrical conversion efficiency. The heterojunction of ZnO-NWs/MWCNTs provides potential applications in the field of photocatalysis and photoelectrical devices.