Preparation of black hierarchical porous ZnO and its photocatalytic activity under visible light

Black hierarchical porous ZnO was prepared by oxidation of nano-porous Zn/ZnO sample obtained from the Al-Zn alloy etched in an NaOH aqueous solution, and was characterized by XRD, SEM, TEM, BET, EDS and UV-Vis spectrophotometer measurements. The results showed that the ZnO appeared black in the sunlight and its reflectivity was approximately 19.5% in the wavelength range from 370 nm to 700 nm. The Black ZnO sample exhibited a hierarchical porous structure consisting of nanosheets with uniformly distributed mesopores , that gives rise to a high specific surface area of about 36 m2/g. Compared to the ZnO nanopowders and TiO2 (P25), black porous ZnO exhibited excellent photocatalytic activity in the degradation of a methyl orange solution under visible light.