Optical and photocatalytic properties of a ZnO@C core/shell sphere with rich oxygen vacancies

Abstract

We develop a novel method to prepare an oxygen-deficient ZnO@C core/shell based on a traditional hydrothermal reaction, and investigate the role of the carbon core and oxygen vacancies in the photocatalytic activity and photoluminescence processes. The heterojunction between the carbon core and zinc oxide could serve as a transport channel to promote photo-generated electrons to move to carbon from the conduction band (CB) and decrease recombination of the electron–hole pairs without loss of light absorption. Detailed analyses based on Raman, EPR and X-ray photoelectron spectroscopy (XPS) revealed that the ZnO@C nanostructures had more oxygen vacancies compared with ZnO, and these could act as donor energy levels and contribute to an enhanced concentration of charge carriers. Due to the presence of a carbon core that acts as a charge separation center, and the synergism with the oxygen vacancy, the ZnO@C samples showed enhanced photocatalytic activity for methyl orange (MO) degradation.