Photocatalytic study of Ni-N-codoped TiO2 nanoparticles under visible light irradiation

Abstract

In present paper pure and Ni-N-codoped TiO2 nanoparticles have been synthesized via sol gel technique. Crystal phase formation of as synthesized nanoparticles was determined from x-ray diffraction which confirms the existence of anatase phase of TiO2. The average crystalline size was determined from x-ray diffraction and estimated from Transmission Electron Micrographs found to vary from 24.8 nm to 10.2 nm. The morphology was studied by Field Emission Scanning Electron Microscopy and reveals that the synthesized nanoparticles are highly crystalline, spherical and small agglomerated. It is observed that on doping the agglomeration decreases and is due to relative rates of growth process. The band gap energy was calculated from UV–visible absorption spectroscopy and found to be 3.12, 1.81, 1.69 and 1.53 eV respectively. The appearance of emission bands at 453, 470, 483 and 494 nm in Photoluminescence spectra could be arising from defect energy states caused by oxygen vacancies within the forbidden region of TiO2.The structural formation of the synthesized nanoparticles is investigated from Fourier-transform-infrared and Energy dispersive x-ray spectroscopy measurements. Photocatalytic degradation efficiency of as synthesized nanoparticles against two different dyes (Congo red and Methyl orange) was investigated under visible light source of wavelength 420–520 nm and is found to increase with dopant concentration (x). It is observed that the increase in Photocatalytic degradation efficiency of synthesized nanoparticles is attributed to decrease in carrier recombination rate arises from the decrease in band gap energy. On the basis of these observations it is concluded that the increase in Photocatalytic activity is due to increase in surface area arises from the decrease in average crystalline size of the synthesized nanoparticles.