Effects of Precursor pH Value and Calcination Temperature on Photocatalytic Properties of Ni-Fe Codoped ZnO Nanoparticles

(Ni, Fe)-codoped ZnO powder was synthesized by a sol-gel process, using oxalic acid zinc as the zinc source. Effects of the pH value of the precursor solution and the calcination temperature on the photocatalytic degradation efficiency of (Ni, Fe)-codoped ZnO powder were studied by using methyl orange as the degradation object. The structures, morphology and ingredients were characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The results show that all the samples are polycrystalline with a nanocrystal size of about 20~30nm. The methyl orange solution (8 mg/L) was degraded by more than 50% in 12 hours under the irradiation of natural light in the presence of the (Fe, Ni)-codoped ZnO sample synthesized under these conditions: the doping concentrations of both Ni, Fe are 1%, the pH of the precursor solution is 7.5, and the calcination temperature is 375°C. The photocatalytic degradation mechanism of (Ni, Fe)-codoped ZnO powder is discussed qualitatively, based on the microstructure analysis.