Facile synthesis of mesoporous N doped zirconium titanium mixed oxide nanomaterial with enhanced photocatalytic activity under visible light

Abstract

The present paper deals with a hydrazine mediated synthesis of high surface area and thermally stable N-doped zirconium titanium mixed oxide with enhanced photocatalytic activity towards reduction of selenium (VI) to metallic Se 0 under visible light. Materials were synthesized at pH ¼ 2 by varying the hydrazine concentration and characterized by XRD, TEM, BET method, XPS, Raman spectroscopy and UV-vis solid state spectra. Presence of low amount of zirconium oxide (10 wt%) helps in phase stabilization and maintains the porous structure even at higher calcinations temperature in comparison to that of pure titania. XPS spectrum justifies the presence of nitrogen and Ti 3+ in the material due to the decomposition reaction of hydrazine. Hydrazine controls the nitrogen content, surface area and the formation of oxygen vacancy in the material. Investigation of metal oxide to hydrazine ratio on the overall surface properties and photocatalytic activity indicates that the 1 : 6 ratio is the optimum composition for the best result. Surface area and pore volume increases to 298 m 2 /g and 0.323 cm 3 /g. The obtained material (TiZr-6N-400) is found to reduce selenium (VI) to selenium (0) under visible light within only 45 min of reaction. Increased photocatalytic activity under visible light is mostly due to the synergistic effect of substantial nitrogen doping, high surface area and presence of oxygen vacancy.

Synthesis and Catalytic Applications of Non-Metal Doped Mesoporous Titania

“…The N-mp-TiO 2 particles were used for the conversion of azoxybenzene to amines or 2-phynylindazoles with methanol using a 365 nm medium-pressure mercury lamp. In addition to introducing N and Ti 3+ , hydrazine increased the surface area from 74 to 134 m 2 /g due to hydrazine decomposition [134,172]. The yield of 4,4 -azoxyanisole by catalytic reductive cleavage on N-mp-TiO 2 (95.7%) in methanol under UV (365 nm) light illumination is higher than that on undoped mp-TiO 2 (60.3%) and P25 (50.6%).…”

“…However, with hydrazine (N 2 H 4 ), titania is expected to be co-doped with both Ti 3+ and N and is therefore to synergistically absorb more visible light and potentially be a more effective redox catalyst than TiO 2 -doped with either species alone. Aman et al explored this concept using Ti 3+ and N-mp-TiO 2 nanoparticles for enhanced photocatalytic activity under visible light [134]. The Ti 3+ /N-mp-TiO 2 showed higher photocatalytic reduction of selenium to metallic Se • under visible light illumination compared to undoped TiO 2 .…”

“…This in-situ formed ammonia and nitrogen (and possibly unstable radical species) act as sources of nitrogen for doping [134]. Selvam et al prepared N-mp-TiO 2 particles by wet impregnation with hydrazine [172].…”

“…Hydrogen, boron, carbon, nitrogen, fluorine, iodine, sulfur, and phosphorus have been used in this capacity, but nitrogen has been studied most extensively. Until now, various approaches to incorporate nitrogen atoms into titania have been reported, such as doping during film sputtering [131], annealing under ammonia gas [12], ion implantation [132,133], hydrazine treatment [134][135][136], urea treatment [137][138][139], treatment of sol-gel titania with nitrogen-containing organics [140], electrochemical processing [141], chemical vapor deposition [142], and plasma techniques [11,13,35,[143][144][145][146][147][148][149][150]. Most of the above doping methods require high temperature treatment and complicated or expensive equipment.…”

Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

“…They also claimed that the doping of Zr ions in TiO 2 lattice could reach about 30%. Recent reports show that the doping of zirconium in the lattice of TiO 2 prevented the anatase to rutile phase transformation during calcination [16][17][18]. Schiller et al observed that Zr-doped TiO 2 showed a high phase stability and the anatase-type structure was maintained even after heat treatment at 800°C [18].…”