Synthesis and application of aluminum substituted ZnO nanowires on carbon fibers photocatalyst for the removal of methylene blue dye from aquatic mediums

In this research, pristine and aluminum substituted ZnO nanowires grown on carbon fibers synthesised by hydrothermal method. The effect of Al concentration on morphology, structure, optical properties and photocatalytic activity on methylene blue was investigated. The aluminum concentration values of 0.5 %, 1 %, 5 % and 10 % of Zn(NO3)2·6 H2O concentration were tested. Resulting structures were characterized by scanning electron microscopy, X-ray Diffraction, diffuse reflectance spectroscopy and UV-Vis diffuse reflectance spectroscopy. XRD results indicates that pristine and aluminum substituted ZnO nanowires has hexagonal zincite crystal structure. The changes of crystal size, crystal parameters, strain and stress with aluminum substitution were investigated. Increasing concentration of aluminum reduced the crystallinity of ZnO. A dramatic change was seen in crystallite size from 40.78 nm to 22.73 nm. Distortion is seen on crystal structure of substituted ZnO causing stress due to different ionic radii between Zn2+ and substituent ions. Tensile stress of 1.38 Pa is calculated for aluminum substituted ZnO nanowires. Smaller ionic radii of aluminum causes positive tensile stress. Optical band gap of structures was analysed. Al substitution reduces the band gap of ZnO NWs/CFs. DRS results shows that Al incorporation led to a 0.05 eV decrease in the bandgap of ZnO NWs/CFs structure. Photocatalytic activity of pristine and aluminum substituted ZnO nanowires on carbon fibers structures were tested on degradation of methylene blue (MB). Al substitution enhances the photocatalytic activity of ZnO nanowires coated on carbon fibers. 1 % Al substituted ZnO NWs on CFs demonstrated highest degradation efficiency with 0.9879 h−1 kinetic rate.