Understanding the Photocatalytic Activity of Sodium Hexatitanate Nanoparticles for Pollutants Degradation: A Spectroscopic Insight

Abstract

Sodium hexatitanate (Na 2 Ti 6 O 13 ) nanoparticles have been synthesized by the hydrothermal method with microwave and conventional heating, after which their photocatalytic properties toward an azo dye pollutant degradation have been investigated. Insights into the dynamics and reactivity of the species involved in the photocatalytic mechanism of the (Na 2 Ti 6 O 13 ) samples were precisely investigated, for the first time, by X-band electron paramagnetic resonance (EPR) spectroscopy under different experimental conditions. X-ray diffraction structural analysis revealed that all samples crystallized in a monoclinic C2/m structure, with different short-range structural order according to the employed heating, as indicated by Raman. Field-emission scanning electron microscopy and transmission electron microscopy results revealed the formation of rod-and fiber-like nanoparticles with different diameters and lengths. EPR measurements indicated the presence of different Ti 3+ point defects and F centers in the samples. X-ray photoelectron spectroscopy analysis proved the presence of oxygen-related defects, but no Ti 3+ was detected on the surface. Spin trapping experiments monitored the generation of hydroxyl (OH•) radicals over UV-irradiation time. Various parameters contribute to the photocatalytic activity of the samples; however, the type of defect and particle morphology appeared as key factors for enhanced efficiency. Our study provides significant information about paramagnetic defects in Na 2 Ti 6 O 13 materials and their role in photocatalysis to design other Ti-based photocatalysts.

Enhanced visible-light photocatalytic activity of N-doped C/Na2Ti6O13/TiO2 hollow spheres for efficient dye degradation

“…4 b) showed two peaks at 458.7 and 458.2 eV (Ti 2P 3/2 ) along with 464.3 and 463.8 eV (Ti 2p 1/2 ), indicating the presence of the Ti 4+ state in the product (splitting value of 5.6 eV). This indicates that there was no reduced Ti 3+ (splitting value of 5.2 eV) on the surface of the TiO 2 and NTO compounds [ 16 ]. The high-resolution Na 1s and O 1s spectra of both samples, as shown in Fig.…”

“…This structure allows for active-site activation and delivery of reactants on the surface, offering advantages such as unidirectional electron flow and enhanced charge transfer, making it suitable for modifications with co-catalysts. However, Na 2 Ti 6 O 13 has a large bandgap, limiting its activity to UV light and leading to a high electron-hole recombination rate [ 16 ]. Thus, using Na 2 Ti 6 O 13 alone for visible light catalytic processes is suboptimal.…”

TiO2 Phase Ratio’s Contribution to the Photocatalytic Activity

“…Dyes such as thymol blue, carmine, indigo red, red 120, rhodamine B, methylene blue, and eriochrome black-T are most often used in the textile industry . When they get into wastewater, they become dangerous and cause serious harm to aquatic flora, fauna, and humans. , Photocatalysis is a well-known method, and its history began at the beginning of the 20th century. − However, it reasonably still attracts a lot of attention as an advanced oxidation process used for the photodegradation of toxic compounds and dyes. − To ensure a photocatalytic process, two conditions must be met, using light as an electron exciter and a semiconductor as a process catalyst. Simultaneously, photocatalysts must have electronic structure, charge transport characteristics, and light-absorbing properties.…”

Comparative study of TiO2–Fe3O4 photocatalysts synthesized by conventional and microwave methods for metronidazole removal

“…Its popularity can be attributed to its excellent photocatalytic properties, which make it suitable for the photooxidation of organic pollutants. However, the use of titanium dioxide in industrial wastewater treatment is limited due to certain drawbacks 5 , 6 . One such limitation is the difficulty in separating TiO 2 from the post-process mixture.…”

“…In addition, available scientific reports indicate that microwave radiation determines molecular processes due to differences in the absorption of microwave energy by compounds in the reaction mixture, which causes local temperature changes 26 – 28 . In another study, Teixeira et al 5 synthesized Na 2 Ti 6 O 13 nanoparticles using the hydrothermal synthesis method with a lower concentration of NaOH under soft conditions. It is worth paying attention to the work presented by Gedye et al 29 , who indicate the influence of many factors, such as sample volume, solvent, homogeneous and heterogeneous reactions, reaction vessel size, and power level on microwave-assisted processes.…”