TiO2 photocatalysis: Design and applications

Investigation of the influence of vanadium, iron and nickel dopants on the morphology, and crystal structure and photocatalytic properties of titanium dioxide based nanopowders

Photoactive V, Fe and Ni doped TiO2 (M-TiO2) nanopowders were synthesized by a modified two-step sol-gel process in the absence of additives. Titanium oxychloride, which is a rarely-used TiO2 precursor was used to yield M-TiO2 photocatalysts with preferential photochemical performance in the presence of natural solar irradiation. The obtained samples were calcined at different calcination temperatures ranging from 450 to 800°C to evaluate the influence of the sintering on the physicochemical properties. The properties of the obtained samples were examined by XRF, XRD, Raman spectroscopy, UV-visible DRS, XPS, nitrogen gas physisorption studies, SEM-EDAX and HRTEM analyses. Structural characterization of the samples revealed the incorporation of these transition metal element into TiO2. It was also depicted that the morphology, crystal structure, optical and photochemical properties of the obtained samples were largely dependent on the calcination temperature and the type of dopant used during the preparation process. The photochemical performance of the samples was investigated in the photodegradation of methylene blue in the presence of natural sunlight. The experimental results indicated that the VT600 sample possessed the highest activity due to its superior properties. This study provides a systematic preparation and selection of the precursor, dopant and calcination temperature that are suitable for the formation of TiO2-based heterogeneous photocatalysts with appealing morphology, crystal structure, optical and photochemical properties for myriad of applications.

Photodegradation of estrogenic endocrine disrupting steroidal hormones in aqueous systems: Progress and future challenges

This article reviews different photodegradation technologies used for the removal of four endocrine disrupting chemicals (EDCs): estrone (E1), 17β-estradiol (E2), estriol (E3) and 17α-ethinylestradiol (EE2). The degradation efficiency is greater under UV than visible light; and increases with light intensity up to when mass transfer becomes the rate limiting step. Substantial rates are observed in the environmentally relevant range of pH7-8, though higher rates are obtained for pH above the pKa (~10.4) of the EDCs. The effects of dissolved organic matter (DOM) on EDC photodegradation are complex with both positive and negative impacts being reported. TiO2 remains the best catalyst due to its superior activity, chemical and photo stability, cheap commercial availability, capacity to function at ambient conditions and low toxicity. The optimum TiO2 loading is 0.05-1gl(-1), while higher loadings have negative impact on EDC removal. The suspended catalysts prove to be more efficient in photocatalysis compared to the immobilised catalysts, while the latter are considered more suitable for commercial scale applications. Photodegradation mostly follows 1st or pseudo 1st order kinetics. Photodegradation typically eradicates or moderates estrogenic activity, though some intermediates are found to exhibit higher estrogenicity than the parent EDCs; the persistence of estrogenic activity is mainly attributed to the presence of the phenolic moiety in intermediates.

Synthesis of molecularly imprinted photocatalysts containing low TiO2 loading: Evaluation for the degradation of pharmaceuticals

A molecularly imprinted (MI) photocatalyst containing a low TiO2 loading (7.00-16.60mgL(-1) of TiO2) was prepared via an acid-catalyzed sol-gel route using different classes of pharmaceutical compounds (i.e., Atorvastatin, Diclofenac, Ibuprofen, Tioconazole, Valsartan, Ketoconazole and Gentamicine) as the template. Herein, our main goal was to test the hypothesis that photocatalysts based on molecular imprinting may improve the degradation performance of pharmaceutical compounds compared to that of a commercial sample (Degussa P25) due to presence of specific cavities in the silica domain. To elucidate certain trends between the performance of photocatalysts and their structural and textural properties, as well the effect of the structure of the drugs on molecular imprinting, the data were analyzed in terms of pore diameter, pore volume, surface area, zeta potential and six-membered ring percentage of silica. In comparison to the commercial sample (P25), we have shown that adsorption and degradation were enhanced from 48 to 752% and from 5 to 427%, respectively. A comparison with the control system (non-imprinted) indicates that the increased performance of the MI systems was due to the presence of specific cavities on the silica domain, and the textural and structural aspects also support this conclusion. The MI photocatalyst was reusable for seven cycles of reuse in which approximately 60% of its photocatalytic efficiency was preserved for the system containing Diclofenac as the template.

The chemical, mechanical, and physical properties of 3D printed materials composed of TiO2-ABS nanocomposites

To expand the chemical capabilities of 3D printed structures generated from commercial thermoplastic printers, we have produced and printed polymer filaments that contain inorganic nanoparticles. TiO₂ was dispersed into acrylonitrile butadiene styrene (ABS) and extruded into filaments with 1.75 mm diameters. We produced filaments with TiO₂ compositions of 1%, 5%, and 10% (kg/kg) and printed structures using a commercial 3D printer. Our experiments suggest that ABS undergoes minor degradation in the presence of TiO₂ during the different processing steps. The measured mechanical properties (strain and Young's modulus) for all of the composites are similar to those of structures printed from the pure polymer. TiO₂ incorporation at 1% negatively affects the stress at breaking point and the flexural stress. Structures produced from the 5 and 10% nanocomposites display a higher breaking point stress than those printed from the pure polymer. TiO₂ within the printed matrix was able to quench the intrinsic fluorescence of the polymer. TiO₂ was also able to photocatalyze the degradation of a rhodamine 6G in solution. These experiments display chemical reactivity in nanocomposites that are printed using commercial 3D printers, and we expect that our methodology will help to inform others who seek to incorporate catalytic nanoparticles in 3D printed structures.

Hydrothermal Synthesis of TiO2@SnO2 Hybrid Nanoparticles in a Continuous-Flow Dual-Stage Reactor

TiO2@SnO2 hybrid nanocomposites were successfully prepared in gram scale using a dual-stage hydrothermal continuous-flow reactor. Temperature and pH in the secondary reactor were found to selectively direct nucleation and growth of the secondary material into either heterogeneous nanocomposites or separate intermixed nanoparticles. At low pH, 2 nm rutile SnO2 nanoparticles were deposited on 9 nm anatase TiO2 particles; the presence of TiO2 was found to suppress formation of larger SnO2 particles. At high pH SnO2 formed separate particles and no deposition on TiO2 was observed. Ball-milling of TiO2 and SnO2 produced no TiO2@SnO2 composites. This verifies that the composite particles must be formed by nucleation and growth of the secondary precursor on the TiO2 . High concentration of secondary precursor led to formation of TiO2 particles embedded in aggregates of SnO2 nanoparticles. The results demonstrate how nanocomposites may be produced in high yield by green chemistry.

Applications of Continuous-Flow Photochemistry in Organic Synthesis, Material Science, and Water Treatment

Continuous-flow photochemistry in microreactors receives a lot of attention from researchers in academia and industry as this technology provides reduced reaction times, higher selectivities, straightforward scalability, and the possibility to safely use hazardous intermediates and gaseous reactants. In this review, an up-to-date overview is given of photochemical transformations in continuous-flow reactors, including applications in organic synthesis, material science, and water treatment. In addition, the advantages of continuous-flow photochemistry are pointed out and a thorough comparison with batch processing is presented.

Self-arrangement of nanoparticles toward crystalline metal oxides with high surface areas and tunable 3D mesopores

We demonstrate a new design concept where the interaction between silica nanoparticles (about 1.5 nm in diameter) with titania nanoparticles (anatase, about 4 nm or 6 nm in diameter) guides a successful formation of mesoporous titania with crystalline walls and controllable porosity. At an appropriate solution pH (~1.5, depending on the deprotonation tendencies of two types of nanoparticles), the smaller silica nanoparticles, which attach to the surface of the larger titania nanoparticles and provide a portion of inactive surface and reactive surface of titania nanoparticles, dictate the direction and the degree of condensation of the titania nanoparticles, resulting in a porous 3D framework. Further crystallization by a hydrothermal treatment and subsequent removal of silica nanoparticles result in a mesoporous titania with highly crystalline walls and tunable mesopore sizes. A simple control of the Si/Ti ratio verified the versatility of the present method through the successful control of mean pore diameter in the range of 2–35 nm and specific surface area in the ranges of 180–250 m² g⁻¹. The present synthesis method is successfully extended to other metal oxides, their mixed oxides and analogues with different particle sizes, regarding as a general method for mesoporous metal (or mixed metal) oxides.

Vacuum template synthesis of multifunctional nanotubes with tailored nanostructured walls

A three-step vacuum procedure for the fabrication of vertical TiO₂ and ZnO nanotubes with three dimensional walls is presented. The method combines physical vapor deposition of small-molecules, plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a post-annealing process in vacuum in order to remove the organic template. As a result, an ample variety of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall composition, microstructure, porosity and structure. The fabrication of multishell nanotubes combining different semiconducting oxides and metal nanoparticles is as well explored. This method provides a feasible and reproducible route for the fabrication of high density arrays of vertically alligned nanotubes on processable substrates. The emptying mechanism and microstructure of the nanotubes have been elucidated through SEM, STEM, HAADF-STEM tomography and energy dispersive X-ray spectroscopy. In this article, as a proof of concept, it is presented the straightforward integration of ZnO nanotubes as photoanode in a photovoltaic cell and as a photonic oxygen gas sensor.

Controllable one-pot synthesis of a nest-like Bi2WO6/BiVO4 composite with enhanced photocatalytic antifouling performance under visible light irradiation

In this study, a novel visible-light-sensitive Bi2WO6/BiVO4 composite photocatalyst was controllably synthesized through a facile one-pot hydrothermal method. The Bi2WO6/BiVO4 composite exhibited a perfect nest-like hierarchical microsphere structure, which was constructed by the self-assembly of nanoplates with the assistance of polyvinylpyrrolidone (PVP). The growth mechanism of the Bi2WO6/BiVO4 composite and the effect of its structure on its photocatalytic performance was investigated and proposed. Experimental results showed that the Bi2WO6/BiVO4 composites displayed enhanced photocatalytic antifouling activities under visible light irradiation compared to pure Bi2WO6 and BiVO4. Bi2WO6/BiVO4-1 exhibited the best photocatalytic antifouling performance, and almost all (99.99%) Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria were killed within 30 min. Moreover, the Bi2WO6/BiVO4-1 composite exhibited excellent stability and reusability in the cycled experiments. The photocatalytic antifouling mechanism was proposed based on the active species trapping experiments, revealing that the photo-induced holes (h(+)) and hydroxyl radicals (˙OH) could attack the cell wall and cytoplasmic membrane directly and lead to the death of bacteria. The obviously enhanced photocatalytic activity of the Bi2WO6/BiVO4-1 composite could be mainly attributed to the formation of heterojunctions, accelerating the separation of photo-induced electrons and holes. Furthermore, the large BET surface area combined with the wide photoabsorption region further improved the photocatalytic performance of the Bi2WO6/BiVO4-1 composite. This study provides a new strategy to develop novel composite photocatalysts with enhanced photocatalytic performance for marine antifouling and water purification.

Energy transfer in plasmonic photocatalytic composites

Among the many novel photocatalytic systems developed in very recent years, plasmonic photocatalytic composites possess great potential for use in applications and are one of the most intensively investigated photocatalytic systems owing to their high solar energy utilization efficiency. In these composites, the plasmonic nanoparticles (PNPs) efficiently absorb solar light through localized surface plasmon resonance and convert it into energetic electrons and holes in the nearby semiconductor. This energy transfer from PNPs to semiconductors plays a decisive role in the overall photocatalytic performance. Thus, the underlying physical mechanism is of great scientific and technological importance and is one of the hottest topics in the area of plasmonic photocatalysts. In this review, we examine the very recent advances in understanding the energy transfer process in plasmonic photocatalytic composites, describing both the theoretical basis of this process and experimental demonstrations. The factors that affect the energy transfer efficiencies and how to improve the efficiencies to yield better photocatalytic performance are also discussed. Furthermore, comparisons are made between the various energy transfer processes, emphasizing their limitations/benefits for efficient operation of plasmonic photocatalysts.

Charge Separation in TiO2/BDD Heterojunction Thin Film for Enhanced Photoelectrochemical Performance

Semiconductor photocatalysis driven by electron/hole has begun a new era in the field of solar energy conversion and storage. Here we report the fabrication and optimization of TiO2/BDD p-n heterojunction photoelectrode using p-type boron doped diamond (BDD) and n-type TiO2 which shows enhanced photoelectrochemical activity. A p-type BDD was first deposited on Si substrate by microwave plasma chemical vapor deposition (MPCVD) method and then n-type TiO2 was sputter coated on top of BDD grains for different durations. The microstructural studies reveal a uniform disposition of anatase TiO2 and its thickness can be tuned by varying the sputtering time. The formation of p-n heterojunction was confirmed through I-V measurement. A remarkable rectification property of 63773 at 5 V with very small leakage current indicates achieving a superior, uniform and precise p-n junction at TiO2 sputtering time of 90 min. This suitably formed p-n heterojunction electrode is found to show 1.6 fold higher photoelectrochemical activity than bare n-type TiO2 electrode at an applied potential of +1.5 V vs SHE. The enhanced photoelectrochemical performance of this TiO2/BDD electrode is ascribed to the injection of hole from p-type BDD to n-type TiO2, which increases carrier separation and thereby enhances the photoelectrochemical performance.

The Inhibition Effect of Tert-Butyl Alcohol on the TiO2 Nano Assays Photoelectrocatalytic Degradation of Different Organics and Its Mechanism

The inhibition effect of tert-butyl alcohol (TBA), identified as the •OH radical inhibitor, on the TiO2 nano assays (TNA) photoelectrocatalytic oxidation of different organics such as glucose and phthalate was reported. The adsorption performance of these organics on the TNA photoelectrode was investigated by using the instantaneous photocurrent value, and the degradation property was examined by using the exhausted reaction. The results showed that glucose exhibited the poor adsorption and easy degradation performance, phthalate showed the strong adsorption and hard-degradation, but TBA showed the weak adsorption and was the most difficult to be degraded. The degradation of both glucose and phthalate could be inhibited evidently by TBA. But the effect on glucose was more obvious. The different inhibition effects of TBA on different organics could be attributed to the differences in the adsorption and the degradation property. For instance, phthalate of the strong adsorption property could avoid from the capture of •OH radicals by TBA in TNA photoelectrocatalytic process.

Different hollow and spherical TiO2 morphologies have distinct activities for the photocatalytic inactivation of chemical and biological agents

TiO₂ hollows and spheres are a suitable morphology for photocatalytic decomposition of dimethyl sulfoxide and anti-pathogen performance, respectively.

Molecular weight effects of PEG on the crystal structure and photocatalytic activities of PEG-capped TiO2 nanoparticles

The increasing molecular weight of PEG can increase the water dispersion but decrease the photocatalytic activity of PEG-capped TiO₂.

Enhancement of photocatalytic activity in Tb/Eu co-doped Bi2MoO6: the synergistic effect of Tb–Eu redox cycles

Tb/Eu co-doped Bi₂MoO₆ exhibited higher photocatalytic activity, and the synergistic effect of Tb–Eu redox cycles for facilitating charge separation and restraining recombination was confirmed.

Au@ZnO core–shell nanostructures with plasmon-induced visible-light photocatalytic and photoelectrochemical properties

Au@ZnO core–shell nanostructures exhibit enhanced photocatalysis under both simulated sunlight and monochromatic LED light due to the synergistic effect between the plasmonic Au-nanosphere cores and the semiconducting ZnO shells.

Monodisperse Ag–AgBr nanocrystals anchored on one-dimensional TiO2 nanotubes with efficient plasmon-assisted photocatalytic performance

A novel ternary Ag–AgBr/TiO₂ plasmonic nanotube heterojunction photocatalyst was fabricated, showing a very high-performance for decomposition of organic pollutants.

Molybdenum disulfide quantum dots: synthesis and applications

This review presents the current development of MoS₂QDs with a special focus on their synthesis techniques, properties and their potential in various applications.

Nanoparticle scattering characterization and mechanistic modelling of UV-TiO2 photocatalytic reactors using computational fluid dynamics

A computational fluid dynamic (CFD) model was developed to describe the process performance of a semi-batch annular TiO2-UV photoreactor in an Eulerian framework. The model accounted for the optical behaviour of titanium dioxide (TiO2) suspensions, the flow distribution and the oxalic acid degradation in the reactor. The scattering component of the optical model, explicitly included in the CFD simulations using a TiO2-specific scattering phase function integrated in the radiative transfer equation, was calibrated using an optical goniometer by comparing simulated scattering light profiles against irradiance measurements collected for various TiO2 concentrations and UV wavelengths and subsequently solved by the discrete ordinate (DO) radiation model. Several scattering phase functions were tested against the goniometric measurements confirming that the Henyey-Greenstein (HG) equation was the most appropriate angular distribution function at 254 and 355 nm, irrespective of the TiO2 concentration. Using the calibrated HG function, a new approach for quantifying the absolute values of absorption and scattering coefficients in TiO2 suspensions was proposed. It consists of iteratively solving, using the DO model, the radiative transfer equation for various combinations of absorption and scattering coefficients until the error between observed and predicted angular irradiance measurements is minimized. The accuracy of the optical parameters was verified with independent CFD simulations carried out for an annular photoreactor and already available in the literature. Predicted and simulated irradiance and oxalic acid degradation data were found to be in excellent agreement, confirming the considerable potential of the integrated modelling approach presented in this paper for the design, optimization and scale-up of photocatalytic technologies for water and wastewater treatment applications.

Isotype heterostructure of bulk and nanosheets of graphitic carbon nitride for efficient visible light photodegradation of methylene blue

Isotype heterostructure of bulk and nanosheets of graphitic carbon nitride with effective band gap of 2.62 eV and charge carrier mean lifetime of 21 ns exhibits an efficient visible light photocatalysis.

Efficient photo-degradation of dyes using CuWO4 nanoparticles with electron sacrificial agents: a combination of experimental and theoretical exploration

Photocatalytic process of CuWO₄ in the presence of electron sacrificial agents.

First-principles study of relative stability of rutile and anatase TiO2 using the random phase approximation

By considering high-order correlations using the random phase approximation, rutile is correctly predicted to be more stable than anatase.

Facile synthesis of TiO2-RGO composite with enhanced performance for the photocatalytic mineralization of organic pollutants

Current research reports the synthesis of reduced graphene oxide (RGO)-TiO2 nanocomposite by in-situ redox method and graphene oxide by modified hummers method. The ratio of RGO and TiO2 in the composite was optimized to show best photocatalytic activity for the degradation of targeted pollutants. Optimized (1:10) RGO-TiO2 nanocomposite was characterized by various techniques viz. X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller surface area (BET), Raman and diffuse reflectance spectroscopy (DRS) technique confirming successful formation of nanocomposite. XRD results confirm the presence of anatase phase in RGO-TiO2. Uniform dispersion of TiO2 nanoparticles on RGO could be seen from TEM images. The obtained results of (1:10) RGO-TiO2 showed five-fold and two-fold enhancement for the visible light and UV light, respectively, for the photocatalytic mineralization of methylene blue dye as compared to commercial Aeroxide P25 TiO2. The excellent photocatalytic mineralization activity of (1:10) RGO-TiO2 could be attributed to the enhanced surface area of composite as well as to its good electron sink capability. (1:10) RGO-TiO2 could be recycled easily and was found to be equally efficient even after the fourth cycle for the photocatalytic mineralization of methylene blue dye. The non-selectivity of synthesized composite was checked by the mineralization studies of oxalic acid.

Sunlight as an energetic driver in the synthesis of molecules necessary for life

This review considers how photochemistry and sunlight-driven reactions can abiotically generate prebiotic molecules necessary for the evolution of life.

A stochastic study of electron transfer kinetics in nano-particulate photocatalysis: a comparison of the quasi-equilibrium approximation with a random walking model

A stochastic study was performed in this research, which showed that electron transport to photocatalytic centers cannot reach a quasi-equilibrium state during photocatalysis.

Synthesis, characterization and photo-catalytic performance of meso-porous Si–N co-doped nano-spherical anatase TiO2 with high thermal stability

Meso-porous Si–N co-doped nano-spherical anatase TiO₂ with high thermal stability.

Shape engineered TiO2 nanoparticles in Caenorhabditis elegans: a Raman imaging based approach to assist tissue-specific toxicological studies

C. elegans model organism was fed with commercial and shape engineered titanium dioxide (TiO₂) nanoparticles (NPs). Raman mapping were performed in order to guide specific toxicological studies in those tissues in which NPs were detected.

Facile preparation of N-doped TiO2at ambient temperature and pressure under UV light with 4-nitrophenol as the nitrogen source and its photocatalytic activities

This article reports the facile preparation of N-doped TiO₂(P25) in aqueous media at ambient temperature and pressure under inert conditions with 4-nitrophenol as the nitrogen source.

Simplified sonochemical preparation of titania embedded with selected metals for purification of benzene and toluene

Titania (TiO2) photocatalysts, each embedded with one of six metals (Ag, Ce, Co, Fe, Mg, and Mn), were prepared using a simplified ultrasonic process. The characteristics of the prepared metal-embedded TiO2 (metal-TiO2) were determined using transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, photoluminescence emission spectroscopy, UV-visible spectroscopy, and nitrogen adsorption-desorption. Except for Co-TiO2, the metal-TiO2 photocatalysts showed improved performance for the decomposition of gaseous benzene and toluene, which are two of the most problematic indoor air pollutants that can cause a variety of adverse health symptoms, under daylight lamp irradiation. Photocatalytic activity was greatest for the Mg-TiO2 sample, followed by, in order, the Ag-TiO2, Ce-TiO2, Fe-TiO2, Mn-TiO2, unmodified TiO2, and Co-TiO2 samples. Although Mg-TiO2 showed the least redshift in its light absorption and the highest electron-hole recombination rate among the metal-TiO2 photocatalysts, it yielded the highest photocatalytic activity, likely because of its increased adsorption capacity and anatase composition. The degradation of benzene and toluene over Mg-TiO2 improved as ultrasound treatment amplitude increased from 20 to 37 μm, then decreased gradually as amplitude was further increased to 49 μm. Degradation efficiency also improved as ultrasound operation time increased from 30 to 60 min, then decreased gradually as amplitude was further increased to 90 min. Overall, this process could be utilized to prepare metal-TiO2 photocatalysts with improved performance for the decomposition of gas phase pollutants under daylight lamp irradiation.

Enhanced photocatalytic activity of TiO2 activated by doping Zr and modifying Pd

The photocatalytic activity of 4-CP degradation is apparently enhanced by doping Zr and modifying Pd in TiO₂ (TiO₂–Zr–Pd) under visible light irradiation.

Zinc Oxide Nanoparticles-Immobilized Mesoporous Hollow Silica Spheres for Photodegradation of Sodium Dodecylbenzenesulfonate

ZnO-Immobilized mesoporous hollow silica spheres (ZnO/xMHSS; x = 15, 30, 50 molar ratio of Zn/Si) were synthesized and examined as photocatalysts toward the degradation of sodium dodecylbenzenesulfonate (SDBS). The hollow structures of MHSS and ZnO-immobilized MHSS composite were evidenced by transmission electron microscopy analysis. X-ray diffraction results confirmed the presence of ZnO and a mesoporous structure in the synthesized materials. N2 adsorption–desorption analysis also depicted the formation of a mesoporous structure and the increased surface area for the ZnO/xMHSS materials. Fourier transform infrared spectroscopy analysis revealed the formation of Si–O–Zn bonds due to interaction between ZnO and MHSS. The photocatalytic testing results indicated that all the ZnO/xMHSS materials showed improved efficiencies of 10–21 % toward the photodegradation of SDBS when compared with bare ZnO. Among the prepared materials, ZnO/15MHSS was the best photocatalyst, which photodegraded 68 % SDBS after 1 h reaction. The kinetic study demonstrated that the photocatalytic reaction followed the second-order model.

Synthesis of Carbon Nanotube-Nanotubular Titania Composites by Catalyst-Free CVD Process: Insights into the Formation Mechanism and Photocatalytic Properties

This work presents the synthesis of carbon nanotubes (CNTs) inside titania nanotube (TNTs) templates by a catalyst-free chemical vapor deposition (CVD) approach as composite platforms for photocatalytic applications. The nanotubular structure of TNTs prepared by electrochemical anodization provides a unique platform to grow CNTs with precisely controlled geometric features. The formation mechanism of carbon nanotubes inside nanotubular titania without using metal catalysts is explored and explained. The structural features, crystalline structures, and chemical composition of the resulting CNTs-TNTs composites were systematically characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The deposition time during CVD process was used to determine the formation mechanism of CNTs inside TNTs template. The photocatalytic properties of CNTs-TNTs composites were evaluated via the degradation of rhodamine B, an organic model molecule, in aqueous solution under mercury-xenon Hg (Xe) lamp irradiation monitored by UV-visible spectroscopy. The obtained results reveal that CNTs induces a synergestic effect on the photocatalytic activity of TNTs for rhodamine B degradation, opening new opportunities to develop advanced photocatalysts for environmental and energy applications.