Exploring structural and optical properties of iodine-doped TiO2 nanoparticles in Rhodamine-B dye degradation: Experimental and theoretical investigation

Energy conversion and pollutant degradation are critical for advancing sustainable technologies, yet they often encounter challenges related to charge recombination and efficiency limitations. This study explores iodine-doped TiO2 nanoparticles as a potential solution for enhancing both energy conversion and pollutant degradation. The nanoparticles were synthesized via the sol-gel method with varying iodine precursor concentrations (0.025-0.1 M) and were characterized for their structural, compositional, and optical properties, particularly in relation to their photocatalytic performance in Rhodamine-B dye degradation. X-ray diffraction confirmed a tetragonal anatase crystal structure, with the average crystallite size decreasing from 10.06 nm to 8.82 nm with increase in iodine concentration. Selected area electron diffraction patterns verified the polycrystalline nature of the nanoparticles. Dynamic light scattering analysis showed hydrodynamic radii ranging from 95 to 125 nm. Fourier-transform infrared spectroscopy identified metal-oxygen vibrations at 441 cm⁻1, and electron microscopy confirmed the spherical morphology of the nanoparticles. Elemental analysis detected the presence of Ti, O, and I in the samples. Diffuse reflectance spectroscopy indicated the optical absorption edges for the doped samples in the visible region from which the corresponding band gap values were deduced. Photoluminescence spectroscopy revealed that the sample with 0.1 M iodine exhibit the lowest emission intensity, suggesting reduced charge recombination. Notably, 0.1 M iodine doped TiO2 samples demonstrated the highest photocatalytic efficiency, achieving 82.36% degradation of Rhodamine-B dye within 140 min under visible light. Additionally, ab-initio density functional theory calculations were performed to investigate the structural, optical, and adsorption properties of TiO2, iodine-doped TiO2, Rhodamine-B, and their composites, providing further insight into the enhanced photocatalytic activity observed in the experiments.

Ultrathin Ag2WO4-coated P-doped g-C3N4 nanosheets with remarkable photocatalytic performance for indomethacin degradation

As a metal-free photocatalyst, the photocatalytic activity of graphitic carbon nitride (g-C₃N₄) remains restricted due to an insufficient visible-light absorption capacity, the rapid recombination of photoinduced carriers, and low surface area. Consequently, P-doped g-C₃N₄ (PCN) was successfully prepared via a single -step thermal polymerization technique using phytic acid biomass and urea, which exhibited remarkable photocatalytic activity for the degradation of indometacin (IDM). The IDM degradation rate was 7.1 times greater than that of pristine g-C₃N₄ (CN). Furthermore, Ag₂WO₄ was loaded onto the surface of the PCN, which formed a Z-scheme heterostructure that promoted the separation of photogenerated carriers. According to analyses of the chemical binding states of PCN, P atoms replaced carbon atoms in the CN framework. According to electron localization function analysis, the low ELF values of P-N facilitated the transfer of photoelectrons. The results of active species scavenging experiments confirmed that superoxide radicals were the primary active species in the photocatalytic degradation system. Finally, the photocatalytic degradation pathways of IDM were predicted through the identification of by-products and IDM reaction sites.

Novel synthesis of Bi-Bi2O3-TiO2-C composite for capturing iodine-129 in off-gas

The Bi-Bi₂O₃-TiO₂-C composites were prepared by a sol-gel method and investigated for capturing iodine-129 (¹²⁹I) in off-gas producing from spent fuel reprocessing. Firstly, the optimal process conditions were operated through the orthogonal experiments, showing that the capturing capacity of the optimal composite was calculated about 504.0 ± 19.5 mg/g, which is approximately 2.0-fold higher than that of the commercial silver-exchanged zeolites (AgX). Secondly, the structure and morphology of the Bi-Bi₂O₃-TiO₂-C composite were characterized, suggesting that the Bi is regularly spherical in the shape, coating by the Bi₂O₃, TiO₂ and amorphous carbon. Finally, the mechanism for the iodine adsorption in the Bi-Bi₂O₃-TiO₂-C system was revealed, demonstrating that the iodine was captured by physisorption and chemisorption.

C,N co-doped porous TiO2 hollow sphere visible light photocatalysts for efficient removal of highly toxic phenolic pollutants

Herein, C,N co-doped porous TiO2 hollow sphere visible light photocatalysts were fabricated using biocompatible N-lauroyl-l-glutamic acid as a doped precursor and soft-template by a mild and facile self-assembly soft-template method, followed by calcination at 550 °C in air. The structure, morphology, and surface elemental composition were characterized in detail by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results show that the prepared TiO2 photocatalysts have a porous hollow sphere structure and are co-doped with C and N. The visible-light-driven photocatalytic degradation rates of phenol and 2-chlorophenol are ∼92 and 90%, respectively. The photocatalytic reaction rate constants of phenol and dichlorophen on HPT550 porous TiO2 hollow spheres were about ∼4 and ∼2 times higher than those on P25, respectively. This enhancement is because the C,N co-doped porous TiO2 hollow spheres not only extend the photoresponse to the visible light region as C,N co-doping narrows the bandgap (2.7 eV), but also expose a large number of surface active sites that favor visible-light-driven photocatalysis. Moreover, the porous hollow structure favors multiple reflections of photons in the interior, increasing the utilization ratio of light. It is worth to pay more efforts to the development of visible light photocatalysts and further promote their practical application.

Fabrication and characterization of novel iodine doped hollow and mesoporous hematite (Fe2O3) particles derived from sol-gel method and their photocatalytic performances

In this work, iodine (I) doped hollow and mesoporous Fe₂O₃ photocatalyst particles were fabricated for the first time through sol-gel method. Phase structure, surface morphology, particle size, specific surface area and optical band gap of the synthesized Fe₂O₃ photocatalysts were analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS), BET surface analysis, particle size analyzer and UV-vis diffuse reflectance spectrum (UV-vis DRS), respectively. Also, electrochemical properties and photoluminescence spectra of Fe₂O₃ particles were measured. The results illustrated that high crystalline, hollow and mesoporous Fe₂O₃ particles were formed. The optical band gap values of the Fe₂O₃ photocatalysts changed between 2.104 and 1.93eV. Photocatalytic efficiency of Fe₂O₃ photocatalysts were assessed via MB solution. The photocatalytic activity results exhibited that I doping enhanced the photocatalytic efficiency. 1% mole iodine doped (I-2) Fe₂O₃ photocatalyst had 97.723% photodegradation rate and 8.638×10^-2min^-1 kinetic constant which showed the highest photocatalytic activity within 45min. Moreover, stability and reusability experiments of Fe₂O₃ photocatalysts were carried out. The Fe₂O₃ photocatalysts showed outstanding stability after four sequence tests. As a result, I doped Fe₂O₃ is a good candidate for photocatalysts.

Stable, High-Efficiency Pyrrolidinium-Based Electrolyte for Solid-State Dye-Sensitized Solar Cells

We synthesized a series of pyrrolidinium based dicationic ionic crystals with high melting point and good thermal stability. Research on the crystal structure shows that there are ordered three-dimensional ionic channels in these crystals which is favorable for the ionic conductor to achieve high conductivity and diffusion coefficient. These ionic crystals are applied to electrolyte as matrix in dye sensitized solar cells, and the influence of crystal structure (including the alkylene chain separating two pyrrolidinium rings and anion) versus the device performances are studied by steady-state voltammography, current-voltage trace, and electrochemical impedance spectroscopy. As the solid state electrolyte, an optimized efficiency of 6.02% have achieved under full sunlight irradiation using ionic crystal [C6BEP][TFSI]2. And the device based on this solid electrolyte shows the excellent long-term stability, maintaining 92% of the initial efficiency after 960 h. This study elucidates fundamental the structure of dicationic crystal and provide useful clues for further improvement of solid-state electrolytes in DSSC.

Doping of TiO2 for sensitized solar cells

This review gives a detailed summary and evaluation of the use of TiO2 doping to improve the performance of dye sensitized solar cells. Doping has a major effect on the band structure and trap states of TiO2, which in turn affect important properties such as the conduction band energy, charge transport, recombination and collection. The defect states of TiO2 are highly dependent on the synthesis method and thus the effect of doping may vary for different synthesis techniques, making it difficult to compare the suitability of different dopants. High-throughput methods may be employed to achieve a rough prediction on the suitability of dopants for a specific synthesis method. It was however found that nearly every employed dopant can be used to increase device performance, indicating that the improvement is not so much caused by the dopant itself, as by the defects it eliminates from TiO2. Furthermore, with the field shifting from dye sensitized solar cells to perovskite solar cells, the role doping can play to further advance this emerging field is also discussed.

Theoretical studies of heteroatom-doping in TiO2 to enhance the electron injection in dye-sensitized solar cells

Density functional calculations have been explored to analyze the structural, electronic and charge transfer properties of a doped TiO₂ substrate and catechol–TiO₂ interfaces for dye-sensitized solar cells.

Effective solid electrolyte based on benzothiazolium for dye-sensitized solar cells

Thiaozole/benzothiaozole-based dicationic conductors were synthesized and applied as solid-state electrolyte in dye-sensitized solar cells (DSSCs). X-ray diffraction, scanning electron microscopy, thermal gravimetric analysis, steady-state voltammogram, photocurrent intensity-photovoltage test, and electrochemical impedance spectroscopy are used to characterize the materials and the mechanism of the cell performance. Compared to the traditional monocationic crystals, the dicationic crystals have a larger size and can provide more opportunities to fine-tune their physical/chemical properties. As a consequence, this solid-state electrolyte-based DSSC achieved photoelectric conversion efficiency of 7.90% under full air-mass (AM 1.5) sunlight (100 mW·cm(-2)).