Green Synthesis of N/Zr Co-Doped TiO2 for Photocatalytic Degradation of p-Nitrophenol in Wastewater

Abstract

TiO2 prepared by a green aqueous sol–gel peptization process is co-doped with nitrogen and zirconium to improve and extend its photoactivity to the visible region. Two nitrogen precursors are used: urea and triethylamine; zirconium (IV) tert-butoxide is added as a source of zirconia. The N/Ti molar ratio is fixed regardless of the chosen nitrogen precursor while the quantity of zirconia is set to 0.7, 1.4, 2, or 2.8 mol%. The performance and physico-chemical properties of these materials are compared with the commercial Evonik P25 photocatalyst. For all doped and co-doped samples, TiO2 nanoparticles of 4 to 8 nm of size are formed of anatase-brookite phases, with a specific surface area between 125 and 280 m2 g−1 vs. 50 m2 g−1 for the commercial P25 photocatalyst. X-ray photoelectron (XPS) measurements show that nitrogen is incorporated into the TiO2 materials through Ti-O-N bonds allowing light absorption in the visible region. The XPS spectra of the Zr-(co)doped powders show the presence of TiO2-ZrO2 mixed oxide materials. Under visible light, the best co-doped sample gives a degradation of p-nitrophenol (PNP) equal to 70% instead of 25% with pure TiO2 and 10% with P25 under the same conditions. Similarly, the photocatalytic activity improved under UV/visible reaching 95% with the best sample compared to 50% with pure TiO2. This study suggests that N/Zr co-doped TiO2 nanoparticles can be produced in a safe and energy-efficient way while being markedly more active than state-of-the-art photocatalytic materials under visible light.

How Can the Introduction of Zr4+ Ions into TiO2 Nanomaterial Impact the DSSC Photoconversion Efficiency? A Comprehensive Theoretical and Experimental Consideration

“…Increasing the Zr 4+ content in the material up to 3.7% caused V p ’s increase, and then drop when Zr 4+ content reaches 5.6%, while S p grew from 3.8 to 7.5 nm. The above observations may be concluded that prepared materials have mesoporous structures created by aggregates built of spherical TiO 2 nanoparticles [ 74 ]. Undoubtedly, the structure of used precursors (isopropoxide and n-propoxide alkoxy chains) can act as semi-templates and induce pores’ growth in investigated materials [ 63 ].…”

Heterogeneous Photocatalysis: A Solution for a Greener Earth

“…In the contribution of Benkhennouche-Bouchene et al [4], TiO 2 that was prepared using a green aqueous sol-gel peptization process was co-doped with nitrogen and zirconium to improve and extend its photoactivity to the visible region. For all doped and co-doped samples, TiO 2 nanoparticles with sizes ranging from 4 to 8 nm were formed of anatase-brookite phases.…”

Photocatalytic Degradation of Tobacco Tar Using CsPbBr3 Quantum Dots Modified Bi2WO6 Composite Photocatalyst

“…To the best of our knowledge, there is no previous research on the photocatalytic degradation of PAHs in tobacco tar. Thus, we compared our optimal sample (over 96% degradation in 50 min) with that for PAH removal in water treatment, such as TiO 2 (over 99% in 24 h) [49], ZnO/TiO 2 (98% in 2 h) [50], TiO 2 (over 66% in 39 min) [51], Evonik P25 (70% in 8 h) [52] and Pr/TiO 2 (over 99% in 3 h) [53]. To investigate the photodegradation process, electron paramagnetic resonance (EPR) spectra were employed to confirm the generated reactive radicals under simulated solar light.…”