Enhanced visible photoelectrochemical properties of ZnO/CdS core/shell nanorods and their correlation with improved optical properties

Abstract

ZnO/CdS core/shell nanorods (NRs) constructed of ZnO NR cores and CdS coating shells were fabricated by hydrothermally growing ZnO NRs and pulsed laser depositing CdS coatings on the grown ZnO NRs. The fabricated ZnO/CdS NRs were characterized by field-emission scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, X-ray diffraction, and Raman backsattering spectroscopy. The optical and photoelectrochemical properties were evaluated and their correlation was studied. The ZnO cores and CdS shells are both in a hexagonal wurtzite structure with c-axis orientation. Compared with the bare ZnO NRs, the heterostructured ZnO/CdS NRs exhibit improved optical properties including strong visible light absorption and quenched photoluminescence. The former facilitates the generation of electron-hole pairs by visible optical excitation, and the latter reveals the suppressed radiative recombination of photogenerated charges and hence efficient charge transfer and separation. Correlated with the improved optical properties and charge behaviors, the ZnO/CdS NRs show high visible photoelectrochemical activity and excellent photoswitching property, and high visible light harvesting efficiencies can be expected for the ZnO/CdS NRs.