Enhanced photocatalytic performances of ZnO with Na doping and graphene oxide quantum dots

Abstract

ZnO and Na0.02Zn0.98O thin films were prepared by sol–gel method. Na0.02Zn0.98O/GOQDs was prepared by spin-coating the graphene oxide quantum dots (GOQDs) on the Na0.02Zn0.98O thin film. XRD result indicates that Na doping and modification of GOQDs does not change the crystal structure but promote the growth of ZnO crystal. The larger absorbance of the Na0.02Zn0.98O/GOQDs in the wavelength range of 400–500 nm may be attributed to the blue absorbance of GOQDs. The orange-yellow emission of the samples may be derived from synthesis of Oi and Vo. PL result indicates that the Na doping in ZnO decreases the amount of oxygen-related Oi and VO defects, but the GOQDs has little effect on Oi and VO. The photocatalytic activity of Na0.02Zn0.98O can be enhanced by Na-doping. The surface Na interstitial defects could serve as favorable trap sites of the electrons or holes to reduce their recombination and are benefit to enhance the photocatalytic activity of the Na0.02Zn0.98O photocatalyst. In addition, the photocatalytic activity of Na0.02Zn0.98O/GOQDs is higher than that of Na0.02Zn0.98O. The result indicates that appropriate graphene oxide can serve as an electron trapper and retard the recombination of electron–hole pairs.