Characterization and photoreactivity of N-, S-, and C-doped ZnO under UV and visible light illumination

Abstract

N-, S-, and C-doped ZnO (N,S,C-ZnO) particles were synthesized from thiourea and zinc sulfate via a precipitation method and were characterized by XRD, XPS, UV–vis spectroscopy, and BET techniques. The photocatalytic activities of the N,S,C-ZnO samples were evaluated by the degradation of acid orange 7 (AO7) and phenol under UV and visible light illumination. XRD results showed that crystallization of the N,S,C-ZnO samples was not well developed after calcination below 700 °C. XPS results suggested that N, S, and C atoms in the samples were predominantly in the bonds of Zn N, Zn S and Zn C after calcination at 500 °C, and were transformed to oxidized forms at 800 °C. UV–vis spectroscopy indicated that dopants N,S,C-species can shift the absorption edge to the visible light region. Incorporating N,S,C-species at appropriate quantities reduced the crystal size and increased the surface area of ZnO samples. The visible light activity of the N,S,C-ZnO samples was confirmed by degradation of phenol. The optimal molar ratios of thiourea to zinc sulfate are 1 and 2 for the highest photocatalytic activities under UV and visible light illumination, respectively. Under visible light illumination, AO7 probably degrades through both the photocatalytic and photosensitized pathways as a result of visible light absorption by N,S,C-ZnO and AO7.