Defect rich ZnO nanosheets of high surface area as an efficient visible light photocatalyst
Abstract A facile ultra rapid solution method was developed to fabricate ZnO nanosheets with tunable BET surface area and rich oxygen vacancy defects. The addition of 1 mol L 1 Na2SO4 led to an increase of BET surface area of ZnO nanosheets from 6.7 to 34.5 m2/g, through an electrostatic controlled growth and self assembly mechanism. Detailed analysis based on Raman scattering, room temperature photoluminescence, X ray photoelectron spectroscopy and electron spin resonance revealed that the as prepared ZnO nanosheets were rich in oxygen vacancies. Increased BET surface area led to a further increase of surface oxygen vacancy concentration. The rich oxygen vacancies promoted the visible light absorption of the ZnO nanosheets, leading to high photocurrent responses and photocatalytic activities towards the degradation of rhodamine B (apparent rate constants, k 0.0179 min 1) under visible light illumination (l 420 nm) about 13 and 11 times higher, respectively than that of ZnO nanoparticles with few oxygen defects. In addition, the high surface area ZnO nanosheets could be effectively hybridized with Ag3PO4 nanoparticles, resulting in a further enhancement of the visible light photocatalytic performance (k 0.0421 min 1) This increase in performance was attributed to the increased visible light absorption as well as the energy level matching, the latter leading to efficient charge transfer between oxygen vacancy rich ZnO nanosheet and Ag3PO4, suggesting a synergistic effect of surface oxygen vacancies and Ag3PO4 coupling.