Preparation Of Ni - Fe Co - Doped Nano - ZnO And Its Photocatalytic Activity

ZnO with a wide direct band gap (Eg) of3.37eV at room temperature has attracted greatattention because of its low prices and low toxicity. Herein we report on the synthesis of nanoZnO and Ni-Fe codoped catalysts with controllable particle size，morphology and surfaceproperites through a simple green，cheap and easy method for industrial technology. Thesurface modifications to the pure ZnO and Ni-Fe codoped ZnO catalysts were investigated inorder to design an optimized catalyst structure. The main content and innovations aresummarized as follows．We were focused on the crystal structure and band structure of (Ni,Fe)-codoped ZnO and its surface photocatalytic activity in response to either ultraviolet orvisible light.Using oxalic acid zinc as zinc source, ethanol as solvent and ethylene glycol as stabilizer,we synthesized (Ni, Fe)-codoped ZnO powder by sol-gel process. We study effects of pHvalue and temperature on the Fe, Ni doped ZnO powder on the photocatalytic degradationefficiency. The products were characterized by X-ray diffraction (XRD), scanning electronmicroscopy (SEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectra(PL). The structure, morphology and ingredient were characterized respectively.We used methyl orange as organic pollutant simulacrum to explore the correlationbetwenn the structure and photocatalytic activity of nano zinc oxide. The environmentalfactors of photocatalytic reaction were investigated. We further explored the photocatalyticmechanism of zinc oxide. The results indicate Ni-Fe effectively doped and uniformlydispersed ZnO nanoparticles were obtained by a sol-gel method. Due to the interreaction ofFe and Ni, zinc oxide particles are formed with certain dispersion, the incorporation of twotransition metals reduces the crystallinity and degree of polymerization. All the ZnO samplesexhibit the wurtzite structure. Changes in the pH value of the precursor solution, calcinationtemperature and catalytic environment will affect on the strength of the thin film diffractionpeak and preferential orientation. We discussed the catalytic performance for differentsamples and corresponding catalytic mechanisms for the case that ZnO powder acts ascatalyst under the irradiation of sunlight in September in Chengdu. The results show that allthe samples are of polycrystalline with the nanocrystal size of about20~30nm. For the (Fe, Ni)-codoped ZnO sample synthesized under the conditions: both the doping concentration ofNi, Fe are at1%, pH of the precursor sol is7.5, and calcination temperature is375℃, thedegradation rate of methyl orange solution (8mg/L) can reach above50%in12hours underthe irradiation of natural light. The photocatalytic degradation mechanism of (Ni,Fe)-codoped ZnO powder was discussed qualitatively based on the microstructure analysis.