Bandgap tuning by controlled growth of Mo doped NiO nanoparticles and their functional role as excellent photocatalytic degradation agent

Abstract

Semiconductor materials are in leading role for elimination of organic pollutants in water with an effective tuning of bandgap and improving their photocatalytic activity. Pristine and Mo-doped (0, 1, 2, 3, 4 and 6 %) NiO nanoparticles have been synthesized by sol–gel method. The synthesized nanoparticles were examined by XRD, SEM, EDS, UV–visible spectroscopy and photoluminescence (PL) analysis. The synthesized nanoparticles exhibit spherical morphology and their crystallite size decreases with an increase in Mo concentration. The average crystallite size decreases from 67 nm to 44 nm and the drastic reduction in band gap occurs from 3.5 eV to 2.9 eV at 3 wt% Mo doping. The photocatalytic activity against Rhodamine-B (RhB) and methylene blue (MB) showed that the Molybdenum doping improves the performance of NiO photocatalyst. The PL analysis revealed that the Molybdenum substitution in NiO host lattice specifically reduces the recombination rate with an improved photo-efficiency. The reaction kinetics examination showed pseudo-first-order kinetics with an improved rate constant. The sample containing 3 wt% Mo doped NiO showed highest efficiency among all the prepared samples. The sample with 3 wt% doping shows 90% degradation after 90 min when using against MB dye, whereas with RhB dye it shows 98% degradation in 120 min. The retention of high performance after five consecutive cycles confirms the reusability of synthesized nanoparticles.