Honeycombed Au@C-TiO2-Xcatalysts for enhanced photocatalytic mineralization of Acid red 3R under visible light

Bio-inspired synthesis of N-doped TiO2/C nanocrystals using jellyfish mucus with high visible-light photocatalytic efficiency

Non-metal doping of titanium dioxide (TiO2) has been widely investigated, because it can facilely improve the optical response of TiO2 under visible light excitation in environmental pollution treatments. In the ongoing efforts, however, little consideration has been given to the use of harmful marine organisms as dopants. Here, we employed the natural mucus proteins of the large harmful jellyfish Aurelia coerulea and Nemopilema nomurai, which have frequently bloomed in East Asian marginal seas in recent decades, to synthesize mesoporous nitrogen-doped TiO2 nanocrystals modified with carbon (N-TiO2/C) by a simple hydrothermal method. These nanocrystals were composed of predominantly anatase phase and a small amount of brookite phase TiO2. Their mesoporous structures changed with the variation of the volume ratio of jellyfish mucus added to tetrabutyl titanate (TBT). At the same ratio, larger surface area and pore volume but smaller pore size were observed in N-TiO2/C nanocrystals from N. nomurai rather than A. coerulea. Nitrogen was determinately doped into the lattice of the prepared nanocrystals and the carbon species were modified on their surfaces, which narrowed the band gap, facilitated the separation of photogenerated electron-hole pairs and favored the absorption of visible light, thus improving their visible light photocatalytic activity. The photocatalytic degradation efficiency of Rhodamine B (RhB) under visible light irradiation first increased and then decreased with the gradual increase of the volume ratio of jellyfish mucus proteins to TBT. The maximum reached 97.52% in 20 min from N-TiO2/C nanocrystals synthesized using N. nomurai mucus at the volume ratio of 4 : 1, which showed a remarkably strong visible light absorption, lower band gap energy and smaller electron transfer resistance. These N-TiO2/C nanocrystals also had a relatively stable crystal structure in multiple degradation reactions. The main active species including superoxide radicals (˙O2 -), photogenerated holes (h+) and hydroxyl radicals (˙OH) were found to play a major role in the degradation process of RhB. This study highlights the potential high-value reapplication of harmful jellyfish mucus as a natural organic matrix in fabricating advanced materials with optimized functional properties.

C, F co-doping Ag/TiO2 with visible light photocatalytic performance toward degrading Rhodamine B

The organic pollutants in industrial wastewater continuously endanger human health. Therefore, effective treatment of organic pollutants is very urgent. Photocatalytic degradation technology is an excellent solution to remove it. TiO₂ photocatalysts are easy to prepare and have high catalytic activity, unfortunately, TiO₂ only absorbs ultraviolet light limiting its utilization of visible light. In this study, a facile environmentally friendly synthesis of Ag-coated on micro-wrinkled TiO₂-based catalysts in order to extend the absorption of Visible light. Firstly, a fluorinated titanium dioxide precursor was prepared by a one-step solvothermal method, and the precursor was calcined at high temperature in a nitrogen atmosphere to form a carbon dopant, and then a surface silver-deposited carbon/fluorine co-doped TiO₂ photocatalyst C/F-Ag-TiO₂ was prepared by a hydrothermal method The results showed that the Ag was coated on the wrinkled TiO₂ layer and C/F-Ag-TiO₂ photocatalyst was synthetized successfully. Benefit from the synergistic effect of doped carbon and fluorine atoms in combination with the quantum size effect of the surface silver nanoparticles, the band gap energy of C/F-Ag-TiO₂ (2.56 eV) is obviously lower than anatase (3.2eV). The photocatalyst achieved an impressive degradation rate of 84.2% for Rhodamine B in 4 h, with a degradation rate constant of 0.367 h^-1, which was 17 times higher than that of P25 under visible light. Therefore, the C/F-Ag-TiO₂ composite is a promising candidate as a highly efficient photocatalyst for environmental remediation.

Non-Stacked γ-Fe2O3/C@TiO2 Double-Layer Hollow Nanoparticles for Enhanced Photocatalytic Applications under Visible Light

Herein, a non-stacked γ-Fe₂O₃/C@TiO₂ double-layer hollow nano photocatalyst has been developed with ultrathin nanosheets-assembled double shells for photodegradation phenol. High catalytic performance was found that the phenol could be completely degraded in 135 min under visible light, due to the moderate band edge position (VB at 0.59 eV and CB at −0.66 eV) of the non-stacked γ-Fe₂O₃/C@TiO₂, which can expand the excitation wavelength range into the visible light region and produce a high concentration of free radicals (such as ·OH, ·O²⁻, holes). Furthermore, the interior of the hollow composite γ-Fe₂O₃ is responsible for charge generation, and the carbon matrix facilitates charge transfer to the external TiO₂ shell. This overlap improved the selection/utilization efficiency, while the unique non-stacked double-layered structure inhibited initial charge recombination over the photocatalysts. This work provides new approaches for photocatalytic applications with γ-Fe₂O₃/C-based materials.

Steered polymorphic nanodomains in TiO2 to boost visible-light photocatalytic oxidation

A breakthrough in enhancing visible-light photocatalysis of wide-bandgap semiconductors such as prototypical titania (TiO₂) via cocatalyst decoration is still challenged by insufficient heterojunctions and inevitable interfacial transport issues. Herein, we report a novel TiO₂-based composite material composed of in situ generated polymorphic nanodomains including carbon nitride (C₃N₄) and (001)/(101)-faceted anatase nanocrystals. The introduction of ultrafine C₃N₄ results in the generation of many oxygen vacancies in the TiO₂ lattice, and simultaneously induces the exposure and growth of anatase TiO₂(001) facets with high surface energy. The photocatalytic performance of C₃N₄-induced TiO₂ for degradation of 2,4-dichlorophenol under visible-light irradiation was tested, its apparent rate being up to 1.49 × 10⁻² min⁻¹, almost 3.8 times as high as that for the pure TiO₂ nanofibers. More significantly, even under low operation temperature and after a long-term photocatalytic process, the composite still exhibits exceptional degradation efficiency and stability. The normalized degradation efficiency and effective lifespan of the composite photocatalyst are far superior to other reported modified photocatalysts.

A novel TiO₂-based composite material composed of in situ generated biomimetic polymorphic nanodomains including carbon nitride (C₃N₄) and (001)-/(101)-faceted anatase nanocrystals is reported.

Tragacanth gum mediated green fabrication of mesoporous titania nanomaterials: Application in photocatalytic degradation of crystal violet

Water remediation is a crucial subject in present century. Hence, several processes have been used for this aim, which the photodegradation method with high activity, cost-effectiveness, and durability has been remarkable. In this project, the various novel mesoporous Titania nanomaterials (MTN) were green synthesized using Tragacanth gum as coupling agent. The effect of calcination times on the crystalline structure of the resulted MTNs was examined. MTNs displayed the dramatically specific surface area with negative surface charge and nano-sheet structure, and they applied for photodegradation of crystal violet under ultraviolet irradiation due to proper band gaps energy. The obtained MTN in 8 h calcination time (MTN-8) showed the best photoreduction activity. Also, the superoxide radicals, electrons, and hole pairs represented the main degradation agents as the reduction rate of crystal violet. Next, the transformation pathways were proposed, which could be transformation singlet oxygen addition, hydroxyl addition, and N-demethylation reactions.

Enhancement of the adsorptive performance of TiO2nanoparticles towards methylene blue by adding suspended nanoparticles of Pt: kinetics, isotherm, and thermodynamic studies

Methylene blue (MB) is one of the most dangerous dyes found in numerous industries' wastewaters. Thus, the effect of suspended Pt nanoparticles (NPs) on the adsorption capability of TiO₂NPs towards MB was investigated in this research. Factors affecting (adsorbate initial concentration, agitation time, solution pH, and temperature) the adsorption capacity of MB on the modified TiO₂NPs were also studied. It was found that the first two factors have a positive effect, the temperature has an adverse impact, and the maximum uptake was observed when pH is 11. Isotherm parameters of Langmuir, Freundlich, and Timken models were determined. Langmuir's model was found to be the best one for analyzing the experimental data. The adsorption capacities obtained were 100.61, 90.66, and 80.26 mg g^-1at 25 °C, 40 °C, and 55 °C, respectively. 1^storder, 2^ndorder, and intra-particle diffusion kinetic models were utilized to analyze experimental data. It found that these data were explained well by the 2^ndorder model, indicating that this adsorption is chemisorption. Thermodynamic parameters were also determined, and the results obtained suggest that this adsorption is an exothermic and spontaneous process. The findings show that TiO₂NPs modified by suspended Pt NPs will get a strong attraction in the treatment of fluids and wastewaters.

C-,N- and S-Doped TiO2 Photocatalysts: A Review

This article presents an overview of the reports on the doping of TiO2 with carbon, nitrogen, and sulfur, including single, co-, and tri-doping. A comparison of the properties of the photocatalysts synthesized from various precursors of TiO2 and C, N, or S dopants is summarized. Selected methods of synthesis of the non-metal doped TiO2 are also described. Furthermore, the influence of the preparation conditions on the doping mode (interstitial or substitutional) with reference to various types of the modified TiO2 is summarized. The mechanisms of photocatalysis for the different modes of the non-metal doping are also discussed. Moreover, selected applications of the non-metal doped TiO2 photocatalysts are shown, including the removal of organic compounds from water/wastewater, air purification, production of hydrogen, lithium storage, inactivation of bacteria, or carbon dioxide reduction.

Highly efficient core–shell Ag@carbon dot modified TiO2 nanofibers for photocatalytic degradation of organic pollutants and their SERS monitoring

The possible mechanism of enhanced photocatalytic performance of Ag@CDs–TiO₂ hybrid NFs.