Enhanced UV and visible light-driven photocatalytic degradation of tartrazine by nickel-doped cerium oxide nanoparticles

Nickel-doped cerium oxide nanoparticles were synthesized via a simple aqueous co-precipitation method. The synthesized nanoparticles were thoroughly characterized by PXRD, TEM, SEM, EDX, Raman, and UV-vis spectroscopic techniques. XRD study revealed the formation of nanoparticles in their pure phase with fluorite structure. EDX confirmed the doping of nickel in the cerium oxide lattice. The shift in Raman spectra revealed the formation of a solid solution on doping Ni-to CeO2. SEM images revealed considerable agglomeration. TEM analysis asserted the average particle size of 8-10 nm with a well defined spherical shape. The particle size was found to be sensitive to dopant concentration i.e., it decreased with increase in the concentration of the dopant. A comparative UV-visible spectroscopic analysis showed the remarkable red shift in the band gap of nickel-doped cerium oxide nanoparticles. Investigation of photocatalytic activity towards degradation of azo dye tartrazine showed that 3 mol% and 5 mol% Ni-CeO2 nanoparticles exhibited 53.4% and 63.7% photodegradation respectively under visible irradiation while 57.4% and 65.4% respectively under UV irradiation. The study suggests that band gap of cerium oxide nanoparticles can be easily tuned (decreased) by doping of nickel at different concentrations. The observed improved photocatalytic activity upon Nickel doping is attributed to the narrow band gap.