Theoretical studies of the interfacial charge transfer and the effect of vdW correction on the interaction energy of non-metal doped ZnO and graphene oxide interface

This study involves investigation of the interaction taking place in a GO-based nitrogen-doped ZnO (N-ZnO–GO) nanocomposite using density functional theory approach. The effects of immobilization of N-doped ZnO [N-ZnO (001)] onto the surface of GO sheet on the interfacial charge transfer, surface chemical stability, band structure, and the capability of the composite to absorb light in the visible region were explored. 3-D charge density plot of the stable composite shows that there was a considerable charge transfer between N-ZnO surface and GO sheet. The partial density of states confirms that the transfer of electrons was from the O 2p orbitals of ZnO to the C 2p orbitals of GO. The band gap of N-ZnO (001) (2.26 eV) and N-ZnO (001)–GO (1.21 eV) were observed to be smaller than that of pure ZnO (3.30 eV). The combined effect of doping ZnO with nitrogen which increased the electron density of ZnO at the valence band maximum and the reduced band gap, resulted in more and easier electron transfer and the extension of the photocatalytic activity of the composite into the visible light region. A type II band alignment was observed for the N-ZnO–GO composite and was linked to the reason for enhanced charge separation at the interface and thus the reduced rate of electron–hole recombination. The Van der Waals correction imposed on the system increased the amount of charge transferred at the interface, reduced interlayer distance and thus increased the interfacial interaction energy. These factors provide more insight on the reasons for the enhanced photocatalytic ability of the non-metals doped ZnO–GO composite used in photocatalysis, optoelectronics, and for solar cells purposes.