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Enhanced Photoelectrocatalytic Activity in Ni-TiO2 Nanocomposites Fabricated By Pulse Potential Deposition

Wednesday, 31 May 2017: 08:20
Grand Salon D - Section 19 (Hilton New Orleans Riverside)
S. Mohajeri (Sharif University of Technology)
The Ni-TiO2 single layer nanocomposites were fabricated on copper substrates by the pulse plating (PP) and pulse reverse plating (PRP) techniques. Morphological studies conducted by field emission scanning electron microscopy (FESEM) revealed that pulse potentials and durations affected the microstructure of coatings. The chemical composition of coatings was studied by energy dispersive X-ray system (EDX) and it was found that by the prolongation of current-off durations in PP and anodic cycles in PRP, deposits containing 11.58 wt.% and 13.16 wt.% TiO2 were produced, respectively. The influence of heat treatment temperature on the phase structure of Ni-TiO2 nanocomposites was investigated using X-ray diffraction and it was demonstrated that the anatase to rutile transformation occurred at temperatures higher than 450°C. The hydrophilicity of Ni-TiO2 coatings was evaluated by monitoring the change of water contact angle under the UV illumination. It was observed that the nanocomposite prepared by PRP exhibited the maximum hydrophilicity after 3 hours of heat treatment at 450°C, for which the contact angel prior to UV irradiation was 78.96° and after 1h of UV irradiation it reduced to 13.65°. Surface hydroxyl groups density which account for the photo-induced hydrophilicity of the Ni-TiO2 coating was defined by X-ray photoelectron spectroscopy (XPS), before and after 1h of UV illumination. The results indicated that under the optimized condition, for the coatings prepared by PP and PRP, 12.6% and 15.3% increases were detected in the density of hydroxyl groups. To evaluate the effect of pulse plating parameters on the photocatalytic activity of the Ni-TiO2 coatings prepared by PP and PRP, photo-degradation experiments of methyl orange aqueous solution were carried out under the UV light. The results indicated that TiO2 content, irradiation duration and sintering temperature affected the photocatalytic efficiency of the coatings, and the optimized PP and PRP deposited coatings were capable of disintegrating the methyl orange up to 76.21% and 51.89% after 1 hours of UV illumination. The photoelectrocatalytic degradation of methyl orange by Ni-TiO2 coatings was studied and the effect of different applied potentials was determined. The amounts of methyl orange degraded by the PP and PRP deposited composites under the anodic potential of 600 mV along with 1 hours of simultaneous UV illumination were 75.30% and 89.61%, respectively.