Photocatalytic reduction of CO2 into fuels offers a promising avenue to tackle present energy challenges and mitigate global warming. At present, TiO2 has been widely used in photocatalytic CO2 reduction reactions, and element doping can optimize the band structure of TiO2 to improve the efficiency of photocatalytic CO2 reduction. In this work, TiO2 doped with different content of N was prepared using TiN as the precursor through a simple one-step calcination method. Under optimized conditions, the optimal CO yield of the modified photocatalyst is 41.1 μmol g− 1 h− 1, which is 8 times higher than that of p25 type TiO2. Density functional theory (DFT) calculations confirmed that N-doping can reduce the band gap of TiO2 and decrease the Gibbs free energy of CO2 reduction reaction. In-situ-XPS indicated that N-doping can enhance the activation of CO2 by enriching photo generated electrons. Additionally, In-situ-FTIR spectra were employed to detect intermediates and track variations in the consumption of H2O and CO2, providing deeper insights into the mechanism responsible for enhancing efficiency. Our work addresses the deficiencies of the past and provides more detailed theoretical insights for the accelerated photocatalytic reduction of CO2 by N-doping TiO2.

TiO2/CNT/GO heterostructure nanocomposite was synthesized by solvothermal method for the removal or degradation of methylene blue (MB). The physical and chemical characteristics were assessed by various characterization techniques such as scanning electron microscopy (SEM) confirmed the external and internal morphology of the heterostructure materials with irregular shapes. Transmission electron microscopy (TEM) showed that the internal structure was preserved after incorporating CNTs and GO into TiO2, and the average particle size distribution was determined using an SEM histogram with an average particle size of 85.5 nm. Energy dispersive X-ray spectroscopy (EDS) was performed to evaluate the elemental mapping of heterojunction confirm the presence of C, O, and Ti. X-ray diffraction (XRD) revealed a crystalline nature and the size of as synthesized material was calculated as 17.08 nm. UV–vis spectroscopy (UV–vis) was conducted to observe the optical behavior and light scattering phenomena of heterostructure materials. Various factors, such as different doses of heterostructure (0.1, 0.2, and 0.3 g), dye concentration (10, 20, and 30 ppm), irradiation time (0, 30, 60, 90, and 120 min), were carried out at 25 °C. The TiO2/ CNT/GO heterostructure induced 91% methylene blue (MB) degradation in 120 min with superior cycling stability after regeneration for four cycles. The optimal reaction conditions were adopted to obtain the highest degradation rate using 0.2 g of the heterostructure, 30 ppm MB concentration, 120 min of light irradiation, and 25 °C reaction temperature. The TiO2/ CNT/GO photocatalyst exhibited enhanced kinetic performance, catalytic stability, structural reliability, and reactivity for 91% degradation efficiency of MB.

In this study, anatase TiO2 nano sol (TNS, TiO2 Nano-Sol) was synthesized via a simple sol-gel method under low-temperature and ambient pressure conditions using TiOCl2 as a precursor. The structural and photocatalytic properties of the TNS were systematically investigated as a function of reaction time. X-ray diffraction (XRD) confirmed the formation of the anatase crystal structure as the reaction time increased, while field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) analyses verified the uniform formation of fine anatase nanoparticles, averaging less than 10 nm in size. The synthesized TNS sol enabled the fabrication of transparent TiO2 coatings that retained over 76 % transmittance in the visible light range, as verified by UV-Vis spectroscopy. Photocatalytic activity was evaluated through methylene blue (MB) degradation experiments, which showed that degradation efficiency was enhanced with longer reaction times. Notably, the TNS-48 exhibited superior photocatalytic degradation performance, being approximately three times higher than that of TNS-1 and about twice that of the commercial P25. This study demonstrates that the TNS sol synthesized through a simple sol-gel process can achieve high transparency and excellent photocatalytic properties without requiring hightemperature and high-pressure synthesis. It is expected to be applicable in various photocatalytic fields, such as functional coatings and electrode materials.

This study examines the effects of the TiO2 content and TiO2 position in the core or shell within tubular carbon nanofibers on the photocatalytic activity under visible light. Core–shell tubular carbon nanofiber composites whose cores are filled with TiO2 nanoparticles (PMTi(10)P) are fabricated through coaxial electrospinning and subsequent heat treatment. The PMTi(10)P composites with well-preserved TiO2 nanoparticles in the core part induce more oxygen vacancies, Ti3+ species, chemisorbed oxygen species, and anatase phases, significantly improving the photocatalytic performance. They act as photoelectron traps, allowing more photoelectrons and holes to participate in the photocatalytic reaction and extending the absorbance of TiO2 to the visible light region. The resulting PMTi(10)P photocatalyst exhibits excellent performance of 100% removal of methylene blue within 30 min and maintains nearly 100% removal of 15 ppm methylene blue over 10 regeneration cycles, indicating consistent and stable photocatalytic performance.

Photocatalytically splitting water into hydrogen upon semiconductors has tremendous potential for alleviating environmental and energy crisis issues. There is increasing attention on improving solar light utilization and engineering photogenerated charge transfer of TiO2 photocatalyst because it has advantages of low cost, non-toxicity, and high chemical stability. Herein, oxygen vacancies and cocatalysts (Cu and MoS2) were simultaneously introduced into TiO2 nanoparticles from protonic titanate by a one-pot solvothermal method. The composition and structure characterization confirmed that the pristine TiO2 nanoparticle was rich in oxygen vacancies. The photocatalytic performances of the composites were evaluated by solar-tohydrogen evolution test. The results revealed that both Cu-TiO2 and MoS2- TiO2 could improve the photocatalytic hydrogen evolution ability. Among them, 0.8% Cu-TiO2 showed the best hydrogen evolution rate of 7245.01 μmol·g−1·h−1, which was 3.57 and 1.34 times of 1.25% MoS2- TiO2 (2726.22 μmol·g−1·h−1) and pristine TiO2 material (2028.46 μmol·g−1·h−1), respectively. These two kinds of composites also had good stability for hydrogen evolution. Combined with the results of photocurrent density and electrochemical impedance spectra, the incorporation of oxygen vacancies and cocatalysts (Cu and MoS2) could not only enhance the light-harvesting of TiO2 but also improve the separation and transfer capabilities of light-induced charge carriers, thus promoting water splitting to hydrogen.

In this work, we investigated the photo-degradation performance of MnO2-SiC fiber-TiO2 (MnO2-SiC-TiO2) ternary nanocomposite according to visible light excitation utilizing methylene blue (MB) and methyl orange (MO) as standard dyes. The photocatalytic physicochemical characteristics of this ternary nanocomposite were described by X-ray diffraction (XRD), scanning electron microscopy (SEM), tunneling electron microscopy (TEM), ultraviolet-visible (UV-vis), diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), photocurrent and cyclic voltammogram (CV) test. Photolysis studies of the synthesized MnO2-SiC-TiO2 composite were conducted using standard dyes of MB and MO under UV light irradiation. The experiments revealed that the MnO2-SiC-TiO2 exhibits the greatest photocatalytic dye degradation performance of around 20 % with MB, and of around 10 % with MO, respectively, within 120 min. Furthermore, MnO2-SiC-TiO2 showed good stability against photocatalytic degradation. The photocatalytic efficiency of the nanocomposite was indicated by the adequate photocatalytic reaction process. These research results show the practical application potential of SiC fibers and the performance of a photocatalyst composite that combines these fibers with metal oxides.

Fe3O4/g-C3N4/TiO2 catalyst has been fabricated using a simple ultrasonic method with high photocatalytic activity. The morphology, structure and optical properties of Fe3O4/ g-C3N4/TiO2 were systematically investigated by a variety of characterization techniques. The optimum degradation conditions were investigated by degrading tetracycline (TC) under visible light irradiation. The results showed that the degradation efficiency was the highest when the initial TC concentration was 5.0 mg/L, the pH value was 11 and the catalyst dosage was 1.0 g/L. After 100 min of visible light irradiation, the degradation efficiency of TC achieved at 73.61%, which was 1.64 and 1.19 times that of g-C3N4 and Fe3O4/ g-C3N4, respectively. Moreover, Fe3O4/ g-C3N4/TiO2 had good stability and recyclability. The results of capture experiments showed that ‧O2 − and ‧OH were the main active species during the photocatalytic process, and a possible photocatalytic reaction mechanism of Fe3O4/ g-C3N4/TiO2 catalyst was proposed. This study provides a new way to improve the photocatalytic performance of g-C3N4, which has great potential in degrading pollutants such as antibiotics in wastewater.

Semiconductor-based photocatalytic carbon dioxide ( CO2) reduction is of great scientific importance in the field of alleviating global warming and energy crisis. Surface amine modification and cocatalyst loading on the catalyst surface could improve CO2 adsorption capacity and photogenerated charge separation. Herein, amine-modified brookite–TiO2 ( NH2–B–TiO2) coupled metal species (Cu, Ag, Ni(OH)2) cocatalysts have been successfully synthesized by chemical reduction method. The photocatalytic CO2 reduction results show that the CH4 production rates of NH2– B–TiO2/Cu, NH2– B–TiO2/Ag, and NH2– B–TiO2/Ni(OH)2 are 3.2, 12.5, and 1.7 times that of NH2– B–TiO2 (0.74 μmmol g− 1 h− 1), respectively. Results show the introduction of metal species on the surface of the catalyst enhances the absorption range of sunlight and the photogenerated carrier separation efficiency, resulting in enhancing the performance of photocatalytic CO2 reduction. This work provides a strategy for designing metal species-loaded amine-modified brookite–TiO2 by surface/interface regulation to improve photocatalytic efficiency.

The conversion of CO2 into solar fuels by photocatalysis is a promising way to deal with the energy crisis and the greenhouse effect. The introduction of oxygen vacancy into semiconductor has been proved to be an effective strategy for enhancing CO2 photoreduction performance. Herein, TiO2- x nanostructures have been prepared by a simple solvothermal method and engineered by the reaction time. With the prolonging of reaction time, the oxygen vacancy signal gradually increases while the band gap becomes narrow for the as-synthesized TiO2- x nanostructures. The results show that the TiO2- x-6 h, TiO2- x-24 h, and TiO2- x-48 h samples have the main product of CH4 (more) and CO (less) for CO2 photoreduction. Among the three oxygen vacancy photocatalysts, the TiO2- x-24 h sample shows the highest CH4 generation rate of 41.8 μmol g− 1 h− 1. On the basis of photo/electrochemical measurements, the TiO2- x-24 h sample exhibits efficient electron–hole separation and charge transfer capabilities, thus allows much more electrons to participate in the reaction and finally promotes the photocatalytic CO2 reduction reaction. It further confirms that the optimization of oxygen vacancy concentration could facilitate the photoinduced charge separation and accordingly improve photocatalytic CO2 conversion.

Interest in the use of semiconductor-based photocatalyst materials for the degradation of organic pollutants in a liquid phase has grown, due to their excellent performance and response to the light source. Herein, we fabricated a NiO-SiCTiO2 ternary structured photocatalyst which had reduced bandgap energy, with strong activation under UV-light irradiation. The synthesized samples were examined using XRD, SEM, EDX, TEM, DRS, EIS techniques and photocurrent measurement. The results confirmed that the two types of metal oxides were well bonded to the SiC fiber surface. The junction of the new photocatalyst exhibited a large number of photoexcited electrons and holes. The holes tended to oxidize the water and form a hydroxyl radical, which promoted the decomposition of methylene blue. The close contact between the 2D SiC fiber and metal oxide semiconductors expanded the scope of absorption wavelength, and enhanced the usability of the ternary photocatalyst for the degradation of methylene blue. Among three synthesized samples, the NiO-SiC-TiO2 showed the best photocatalytic effect, and was considered to have excellent photoelectron transfer due to the synergy effect between the metal oxide and SiC.

To build a highly active photocatalytic system with high efficiency and low cast of TiO2, we report a facile hydrothermal technique to synthesize Ag2Se-nanoparticle-modified TiO2 composites. The physical characteristics of these samples are analyzed by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, transmission electron microscopy and BET analysis. The XRD and TEM results show us that TiO2 is coupled with small sized Ag2Se nanoplate, which has an average grain size of about 30 nm in diameter. The agglomeration of Ag2Se nanoparticles is improved by the hydrothermal process, with dispersion improvement of the Ag2Se@TiO2 nanocomposite. Texbrite BA-L is selected as a simulated dye to study the photodegradation behavior of as-prepared samples under visible light radiation. A significant enhancement of about two times the photodegradation rate is observed for the Ag2Se@TiO2 nanocomposite compared with the control sample P25 and as-prepared TiO2. Long-term stability of Ag2Se@TiO2 is observed via ten iterations of recycling experiments under visible light irradiation.

For the purpose of manufacturing a high efficiency TiO2 photocatalyst, B-doped TiO2 photocatalysts are synthesized using a plasma electrolytic oxidation method in 0.5 M H2SO4 electrolyte with different concentrations of H3BO3 as additive. For the B doped TiO2 layer fabricated from sulfuric electrolyte having a higher concentration of H3BO3 additive, the main XRD peaks of (101) and (200) anatase phase shift gradually toward the lower angle direction, indicating volume expansion of the TiO2 anatase lattice by incorporation of boron, when compared with TiO2 layers formed in sulfuric acid with lower concentration of additive. Moreover, XPS results indicate that the center of the binding energy peak of B1s increases from 191.45 eV to 191.98 eV, which suggests that most of boron atoms are doped interstitially in the TiO2 layer rather than substitutionally. The B doped TiO2 catalyst fabricated in sulfuric electrolyte with 1.0 M H3BO3 exhibits enhanced photocurrent response, and high efficiency and rate constant for dye degradation, which is ascribed to the synergistic effect of the new impurity energy band induced by introducing boron to the interstitial site and the improvement of charge transfer reaction.

Transparent, photocatalytic, and self-cleaning TiO2 thin film is developed by TiO2 sol-gel coating on glass and polycarbonate (PC) substrates. Acetyl acetone (AcAc) suppresses the precipitation of TiO2 by forming a yellowish (complex) transparent sol-gel. XPS analysis confirms the presence of Ti2p and O1s in the thin films on glass and PC substrates. The TiO2- sol is prepared by stabilizing titanium (IV) isopropoxide (TTIP) with diethylamine and methyl alcohol. The addition of AcAcsilane coupling solution to the TiO2-sol instantaneously turns to yellowish color owing to the complexing of titanium with AcAc. The AcAc solution substantially improves the photocatalytic property of the TiO2 coating layer in MB solutions. The coated TiO2 film exhibits super hydrophilicity without and with light irradiation. The TiO2 thin film stabilized by adding 8.7 wt% AcAc shows the highest photo-degradation for methylene blue (MB) solution under UV light irradiation. Also, the optimum photocatalytic activity is obtained for the 8.7 wt% AcAc-stabilized TiO2 coating layer calcined at 450 oC. The thin-films on glass exhibit fast self-cleaning from oleic acid contamination within 45 min of UV-light irradiation. The appropriate curing time at 140 oC improves the anti-fogging and thermal stability of the TiO2 film coated on PC substrate. The watermark-free PC substrate is particularly beneficial to combat fogging problems of transparent substrates.

A facile one-pot wet chemical process to prepare pure anatase TiO2 hollow structures using ammonium hexafluorotitanate as a precursor is developed. By defining the formic acid ratio, we fabricate TiO2 hollow structures containing fluorine on the surface. The TiO2 hollow sphere is composed of an anatase phase containing fluorine by various analytical techniques. A possible formation mechanism for the obtained hollow samples by self-transformation and Ostwald ripening is proposed. The TiO2 hollow structures containing fluorine exhibits 1.2 - 2.7 times higher performance than their counterparts in photocatalytic activity. The enhanced photocatalytic activity of the TiO2 hollow structures is attributed to the combined effects of high crystallinity, specific surface area (62 m2g-1), and the advantage of surface fluorine ions (at 8%) having strong electron-withdrawing ability of the surface ≡ Ti-F groups reduces the recombination of photogenerated electrons and holes.

To improve photocatalytic performance, CdS nanoparticle deposited TiO2 nanotubular photocatalysts are synthesized. The TiO2 nanotube is fabricated by electrochemical anodization at a constant voltage of 60 V, and annealed at 500 for crystallization. The CdS nanoparticles on TiO2 nanotubes are synthesized by successive ionic layer adsorption and reaction method. The surface characteristics and photocurrent responses of TNT/CdS photocatalysts are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis spectrometer and LED light source installed potentiostat. The bandgaps of the CdS deposited TiO2 photocatalysts are gradually narrowed with increasing of amounts of deposited CdS nanoparticles, which enhances visible light absorption ability of composite photocatalysts. Enhanced photoelectrochemical performance is observed in the nanocomposite TiO2 photocatalyst. However, the maximum photocurrent response and dye degradation efficiency are observed for TNT/CdS30 photocatalyst. The excellent photocatalytic performance of TNT/CdS30 catalyst can be ascribed to the synergistic effects of its better absorption ability of visible light region and efficient charge transport process.

The coupling of two semiconducting materials is an efficient method to improve photocatalytic activity via the suppression of recombination of electron-hole pairs. In particular, the coupling between two different phases of TiO2, i.e., anatase and rutile, is particularly attractive for photocatalytic activity improvement of rutile TiO2 because these coupled TiO2 powders can retain the benefits of TiO2, one of the best photocatalysts. In this study, anatase TiO2 nanoparticles are synthesized and coupled on the surface of rutile TiO2 powders using a microemulsion method and heat treatment. Triton X-100, as a surfactant, is used to suppress the aggregation of anatase TiO2 nanoparticles and disperse anatase TiO2 nanoparticles uniformly on the surface of rutile TiO2 powders. Rutile TiO2 powders coupled with anatase TiO2 nanoparticles are successfully prepared. Additionally, we compare the photocatalytic activity of these rutile-anatase coupled TiO2 powders under ultraviolet (UV) light and demonstrate that the reason for the improvement of photocatalytic activity is microstructural.

F-containing TiO2 nanopowders are synthesized using simple wet processes (precipitation-based and hydrothermal) from ammonium hexafluorotitanate (AHFT, (NH4)2TiF6) as a precursor to apply as a photocatalyst for the degradation of rhodamine B (RhB). The surface properties of the prepared samples are evaluated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The results confirm that the synthesized anatase TiO2 has sphere-like shapes, with numerous small nanoparticles containing fluorine on the surface. The photocatalytic activity of F-containing TiO2 compared with F-free TiO2 is characterized by measuring the degradation of RhB using a xenon lamp. The photocatalytic degradation of F-containing TiO2 exhibits improved photocatalytic activity, based on the positive effects of adsorbed F ions on the surface.