Enhancing the visible light induced photocatalytic activity in sol-electrospun zinc titanate nanopowders by nitrogen doping

Abstract

Hexagonal phase of Zinc titanate (ZTO) powder obtained by calcining the electrospun sol in the temperature range of 700–800 °C has shown bandgap in the visible region (Perween and Ranjan, 2017) [1]. Owing to this, ZTO can be considered as a candidate material for visible light induced photocatalysis applications, and therefore can serve as a suitable alternative for solar radiation aided treatment of environmental pollutants. Doping ZTO with a suitable dopant atom such as nitrogen can further reduce its bandgap and thereby enhance the efficacy of its catalytic response to solar light. Here we report successful incorporation of nitrogen in zinc titanate with varying fraction of nitrogen using urea as a nitrogen source. Nitrogen incorporation leads to reduction in the bandgap, and thereby improvement in its visible light induced catalytic performance of ZTO towards the degradation of phenol. Presence of nitrogen also promotes the formation of the high-temperature phase of cubic Zn2TiO4. Nitrogen incorporated ZTO (N-ZTO) nanoparticles lead to a reduction in the bandgap from 2.83 eV in un-nitrogenated samples to 2.25 eV in nitrogenated ZTO. A substitutional doping of nitrogen is confirmed by various characterization techniques such as XPS, Raman, and FT-IR which show the presence of Ti–N bonds. Nitrogen incorporation in electrospun samples yields high surface area (122 m2/g) upon calcination, generating surface states that play important role in enhancing the sensitivity to visible light in samples prepared by our technique. The rate constant (k) of the phenol degradation reaction increased to 0.02051 min−1 with N-ZTO as compared to 0.00330 min−1 obtained with ZTO.