Improved visible-light photocatalytic activity of porous carbon self-doped ZnO nanosheet-assembled flowers

Abstract

Hierarchical flower-like C-doped ZnO superstructures (ZnO flowers) assembled from porous nanosheets are obtained by pyrolysis of morphology-analogous Zn5(CO3)2(OH)6 precursors. The prepared ZnO flowers are characterized by X-ray diffraction, thermogravimetic and differential scanning calorimeter analysis, scanning electron microscopy, transmission electron microscopy, N2 sorption measurements, UV-vis diffuse reflectance spectra and X-ray photoelectron spectroscopy. The production of OH radicals on the ZnO surface under visible-light irradiation is detected by a photoluminescence technique using terephthalic acid as a probe molecule. The visible-light photocatalytic activity is evaluated by photocatalytic decomposition of the dye RhB in aqueous solution. The hierarchical organization of nanosheets, the multimode voids between and within porous nanosheets, together with annealing-induced in situ carbon self-doping within the ZnO lattice, account for the enhanced light-absorption capacity, extended light-response range and thus better photocatalytic activity of the ZnO flowers. Furthermore, first-principle density functional theory (DFT) calculation further confirms the C-doping induced red shift in the absorption edges of C-doped ZnO flowers.