Surface Of TiO2 Particles Research Articles

Exploring the Enhancement of Photocatalytic Performance in TiO2 based Hollow Composites: Size Effect of the Adsorbed CeO2 Particles

AbstractThe photocatalytic (PC) behavior of CeO2–TiO2 hollow composites with different heterojunction structures are investigated. The composites are fabricated by combining TiO2 hollow spheres and CeO2 nanoparticles with changing the ratio between Ce and Ti. High‐resolution microscopic and spectroscopic analysis demonstrates that three types of cerium‐bearing structures form on the surface of the titania. The first involves Ce atoms adsorbed onto the surface of TiO2 particles. The second occurs with small CeO2 particles, ≈2 nm in size, resulting from the aggregation of the adsorbed Ce atoms, thus forming a CeO2–TiO2 heterojunction. The last type is obtained through the growth of the CeO2 particles up to 10 nm in size. All the CeO2–TiO2 composites exhibit enhanced photocatalytic degradation of methyl orange under visible light irradiation compared to mere CeO2 or TiO2 nanoparticles. The synergistic effect of these three structures leads to a competition between size effects and interface interactions, which affects the band alignment, the number of defects, and, consequently, the PC activity. The highest PC reaction rate constant under visible light reaches up to 0.017 min−1 and is achieved when the CeO2 nanoparticle size is smaller than its Debye length.

Green fabrication of CuO-egTiO2 composite for photodegradation of organic pollutant under direct visible light illumination

A (CuO-egTiO2) composite coated with copper oxide has been manufactured as a green and facile photocatalyst via Argyreia nervosa leaf extract. The photocatalyst consists of equaixial geometry (egTiO2) particles with copper oxide (CuO) nanocrystals deposited on the TiO2 surface in varying proportions. The structural, morphological, and optical properties of the CuO-egTiO2 photocatalyst nanostructures were inspected via various techniques, through (XRD), (FE-SEM), (DRS), (BET) analysis, (PL) spectra, and (TEM). The results obtained revealed the non-uniform growth of CuO nanocrystals on the surface of TiO2 particles, resembling a (core–shell) structure. The photocatalytic activity of the CuO-egTiO2 nanocomposite was verified in the degradation of Rhodamine B dye (RhB) using an inhomogeneous photocatalytic activation process, with CuO-egTiO2 (10 %) proving to be the most effective photocatalyst under visible light. The effect of the catalyst quantity within concentrations of 0.3–1.8 g/L was studied by exposing aqueous solutions containing the photocatalysts to visible radiation. The dye removal rate was estimated by calculating the remaining concentration, indicating a pseudo-first-order disappearance model with a dye removal percentage of 95.20 %. Additionally, the impact of reactive oxygen species (ROS) types was investigated, The highest photocatalytic degradation rate of 52.16 % was observed when using the inhibitor (EDTA), indicating that the active group contributing to the photocatalytic degradation of RhB is hydroxyl radicals (●OH). At last, in reuse experiments, it was demonstrated that the CuO-egTiO2 (10 %) photocatalyst maintained a remarkable 75.3 % of its initial efficiency even after being recycled for four cycles.

Phenol degradation on the surface of mesoporous TiO2 particles via ligand-to-metal charge transfer under visible light irradiation

Degradation behaviors of phenol from aqueous solution under the blue light irradiation were studied using a series of sol–gel prepared TiO2 particles exhibiting different blue light absorbing abilities. The phenol degradation under the blue light irradiation was most pronounced in the presence of TiO2 sample exhibiting the lowest blue light absorbing ability among the samples, showing no correlations between phenol degradation and light absorbing ability of TiO2 particles. UV-DRS analysis and scavenging experiments revealed that phenol degradation under visible light irradiation can be majorly proceed via the light absorption by the ligand-to-metal-charge-transfer (LMCT).

Defect-induced regulation of crystal growth and phase transition of TiO2 synthesized from Ti-bearing blast furnace slag

Ti-bearing blast furnace slag (TBFS) is an essential secondary Ti resource for TiO2 production. However, the TiO2 is sintered and does not meet the pigment requirements. This study investigated the effect of surface/bulk distribution of defect structures on the crystal growth and phase transition of TiO2 based on the Rietveld method. For the defects of Xn+ (Al3+/Mg2+/Zn2+), the interstitial Xn+ (Xint) is mainly located on the surface of TiO2 particles and inhibits the crystal growth. The substituted Xn+ (Xsub) is primarily located in the bulk and promotes the phase transition. The radius of Xn+ affects the stability of Xint and determines the distribution of Xint/Xsub. Thus, the major defect structures of Al3+, Mg2+, and Zn2+ (increasing radius) are Alint, Mgint/Mgsub, and Znsub, respectively. Based on this, a new co-doping method was proposed. Co-doping modifies the distribution of Xint/Xsub to regulating the crystal growth and phase transition. Finally, TiO2 for pigment with a small particle size (220 ± 60 nm) and high rutile conversion (98.1%) was synthesized from TBFS. The results will help to optimize the process for producing TiO2 pigment from TBFS and provide new insights into the structure regulation of TiO2 materials.

Self-cleaning and photodegradle PVDF separation membranes modified with self-assembled TiO2-g-CS/CNTs particle

This work obtained separation membranes with UV-cleaning performance by adding TiO2-g-CS/CNTs photocatalyst to the PVDF. The positively charged chitosan (CS) and negatively charged carboxylic carbon nanotube (CNTs-COOH) can be self-assembled into the bilayer structure on the surface of TiO2 particles through electrostatic attraction. The presence of many hydrophilic groups in CS and CNTs-COOH significantly improves the hydrophilicity of TiO2-g-CS/CNTs-PVDF membrane, and helps TiO2 to be uniformly dispersed on the upper surface. TiO2-g-CS/CNTs promote the change of pore structure and expand the flux of the modified membrane to 4.5 times that of pure PVDF. Zeta potential demonstrates that the TiO2-g-CS particles successfully attracted CNTs in the PVDF matrix, and the membrane surface was still positively charged. Thus, the combined effect of the positively charged TiO2-g-CS and the highly adsorbed CNTs enhanced the retention of the contaminants. More importantly, there is a charge transfer between the grafted CS and TiO2 interface to obtain a broader light absorption band. The excitation carriers provided by CNTs significantly contribute to the photocatalytic performance after transfer between TiO2 and CS; thus, TiO2-g-CS/CNTs-PVDF produces higher photocatalytic activity for dye molecules (degradation rate > 97 %).

A high performance TiO2 anode modified by germanium and oxygen vacancies for lithium-ion batteries

A TiO2 anode modified by germanium and oxygen vacancies was fabricated using a hydrothermal method with an autoclave at 180 °C, followed by reduction sintering at 600 °C for 5 h in a reducing atmosphere. Germanium was obtained and distributed uniformly on the surface of the anatase TiO2 particles. Oxygen vacancies were identified on the TiO2 surface by electron paramagnetic resonance and X-ray photoelectron spectroscopy. The specific capacity of the Ge@TiO2−x anode was 510 mAh g−1 after 550 charge-discharge cycles. The charge transfer and electrolyte impedance of Ge@TiO2−x were smaller than those of the initial TiO2. The lithium-ion diffusion coefficient in Ge@TiO2−x was 7.87 × 10−13 cm2·s−1, which was significantly higher than that of a commercial TiO2 anode. The germanium and oxygen vacancies in TiO2 provided more active sites for the transport of lithium ions and electrons, thereby reducing the energy barrier, accelerating the charge transfer of lithium ions and enhancing the conductivity and capacity of the Ge@TiO2−x anode.

Photocatalytic Activity of the Blends Based on TiO2 Nanoparticles and Reduced Graphene Oxide for Degradation of Acetaminophen.

The aim of this work is to highlight the influence of blends based on TiO2 nanoparticles and reduced graphene oxide (RGO) on the photodegradation of acetaminophen (AC). To this end, the catalysts of TiO2/RGO blends with RGO sheet concentrations equal 5, 10, and 20 wt. % were prepared by the solid-state interaction of the two constituents. The preferential adsorption of TiO2 particles onto the RGO sheets' surfaces via the water molecules on the TiO2 particle surface was demonstrated by FTIR spectroscopy. This adsorption process induced an increase in the disordered state of the RGO sheets in the presence of the TiO2 particles, as highlighted by Raman scattering and scanning electron microscopy (SEM). The novelty of this work lies in the demonstration that TiO2/RGO mixtures, obtained by the solid-phase interaction of the two constituents, allow an acetaminophen removal of up to 95.18% after 100 min of UV irradiation. This TiO2/RGO catalyst induced a higher photodegradation efficiency of AC than TiO2 due to the presence of RGO sheets, which acted as a capture agent for the photogenerated electrons of TiO2, hindering the electron-hole recombination. The reaction kinetics of AC aqueous solutions containing TiO2/RGO blends followed a complex first-order kinetic model. Another novelty of this work is the demonstration of the ability of PVC membranes modified with Au nanoparticles to act both as filters for the removal of TiO2/RGO blends after AC photodegradation and as potential SERS supports, which illustrate the vibrational properties of the reused catalyst. The reuse of the TiO2/RGO blends after the first cycle of AC photodegradation indicated their suitable stability during the five cycles of pharmaceutical compound photodegradation.

A convenient and environment-friendly method of photo-degradation of graphene oxide in water

Wastewater containing graphene oxide (GO) has become important industrial wastewater due to a sharp increase in graphene oxide production in recent years. In this paper, SnO2 and TiO2 were added into aqueous suspensions of GO to degrade GO particles under UV light irradiation. Dosages of added metal oxides, pH values of the reaction mixture and UV irradiation in photo-degradation procedure were optimized. Photoluminescence and electrochemical impedance spectroscopy spectra were determined to study on separation and transfer of photo-generated electron-hole pairs at the GO/metal-oxide interfaces. Experimental results showed that GO particles were adsorbed on the surface of SnO2 or TiO2 particles via electrostatic attraction. SnO2 (conduction band bottom energy level (EC) = −5.00 eV) and TiO2 (EC = −4.05 eV) were effective photo-catalysts for degrading GO to give CO2 and H2O. Effective photo-catalytic degradation of GO would be contributed to EC values of SnO2 (−5.00 eV) and TiO2 (−4.05 eV) being lower than the lowest unoccupied molecular orbital energy level (ELUMO) value of GO (−3.59 eV). Therefore, metal oxides with low EC values (< −3.59 eV) would be selectable catalysts for degrading GO in wastewater. Similarly, if an EC value of a metal oxide was lower than the ELUMO value of an organic pollutant, the metal oxide would be selectable catalysts for degrading the pollutant in wastewater.

Improvement of anti-aging property of UV-curable coatings with silica-coated TiO2

A series of SiO2 coated TiO2 particles (TiO2@SiO2) were prepared by depositing SiO2 layer on the surface of TiO2 particles via an in-situ hydrolysis condensation of tetraethyl silicate, which was used as UV-shielding fillers to prepare UV-curable coatings. The effect of SiO2 layer on the photocatalytic activity, UV-shielding ability and dispersibility of TiO2 particles was systematically explored. The anti-aging property of the UV-cured coating was determined by color change, surface gloss loss, and surface morphology via accelerated UV aging test. It was found that the presence of a continuous and dense SiO2 layer on TiO2 surface could not only improve the dispersibility of TiO2, but also effectively inhibit the photocatalytic activity of TiO2 without sacrificing its UV-shielding ability, thereby significantly enhancing the anti-aging property of UV-curable coatings. Salt spray test shows that the aged UV-cured coating with TiO2@SiO2 exhibited better corrosion protection behavior than the aged pure resin coating as well as the aged TiO2 coating.

Получение анатазного диоксида титана — наполнителя для специальных герметиков

Current TiO2 technologies are complex and costly in terms of reagents and energy. Due to the high sinterability of the titanium dioxide particles, the calcination of the hydrate precursor requires several grinding stages of the product as well as TiO2 particles surface modification to improve performance, including oil capacity. A solid-phase proccess for the production of anatase titanium dioxide has been developed based on the thermolysis of a crystalline titanium (IV) salt, a semi-product of sulfuric acid processing of sphene concentrate.

Adhesion of Polymer to TiO2 Particles Decreases Photocatalytic Activity of Polyelectrolyte Hydrogel Photocatalyst

AbstractA comparative study on the photocatalytic activity was done for TiO2/poly(acrylamide‐co‐potassium acrylate) composite hydrogels with varying content of potassium acrylate monomer units. The presence of the acrylate units led to the increase in the swelling ratio of hydrogel and to the enhancement of the diffusion of the methyl orange probe dye to the surface of the embedded TiO2 particles. However, the photocatalytic activity was not improved. Microcalorimetry data showed that while the enthalpy of polymer adhesion to the TiO2 particles surface was positive in the case of polyacrylamide and it became negative if acrylate units were included in the polymer network. Likely, the adhesion enhancement occurred due to the electrostatic interaction among acrylate monomer units and surface of TiO2 particles. As a result of polymer adhesion to the active surface of the catalyst particles was partly blocked and the photocatalytic activity of the composite hydrogel diminished.

Electrodeposition of Ni-zirconia or Ni-titania composite coatings from a methanesulfonic acid bath

The study addresses the patterns of formation of Ni-ZrO2 and Ni-TiO2 composite coatings from methanesulfonate and sulfate electrolytes at pH 3. It has been shown that the aggregative stability of the dispersed phase particles is better in the methanesulfonate electrolyte than in the sulfate electrolyte. As a result, at the same volume concentration of the non-metallic phase in both electrolytes, the concentration of particles is larger in the methanesulfonate electrolyte. This ensures the formation of composite coatings from methanesulfonate electrolyte with a content of non-metallic particles increased by 20–30 vol% compared to sulfate electrolyte. A mechanism for forming a composite coating has been proposed, which takes into account the different rates of the metal phase electrodeposition on the electrode surfaces that are free from the dispersed phase or conditionally occupied. A mathematical model of composite coating formation has been developed, which adequately describes the obtained experimental data. Incorporation of the non-metallic phase into the nickel matrix leads to a change in the coating structure and decrease in the sizes of metal grains. It has been found that the physicochemical properties of Ni-ZrO2 and Ni-TiO2 composite coatings depend on the content of non-metallic phase particles in them. It has been revealed that the microhardness of Ni-ZrO2 coatings obtained from methanesulfonate electrolyte is 10 % higher than the microhardness of coatings deposited from sulfate electrolyte, which is due to a higher content of the non-metallic phase. The photocatalytic activity of Ni-TiO2 composite coatings correlates with the content of the dispersed phase in them, which is due to the participation of TiO2 particle surfaces, accessible to irradiation, in the photocatalytic reaction. It has been found that an increased content of the dispersed phase in Ni-ZrO2 and Ni-TiO2 composite coatings obtained from methanesulfonate electrolyte leads to increased values of their microhardness and photocatalytic activity.

Differential Surface Interactions and Surface Templating of Nucleotides (dGMP, dCMP, dAMP, and dTMP) on Oxide Particle Surfaces.

The fate of biomolecules in the environment depends in part on understanding the surface chemistry occurring at the biological-geochemical (bio-geo) interface. Little is known about how environmental DNA (eDNA) or smaller components, like nucleotides and oligonucleotides, persist in aquatic environments and the role of surface interactions. This study aims to probe surface interactions and adsorption behavior of nucleotides on oxide surfaces. We have investigated the interactions of individual nucleotides (dGMP, dCMP, dAMP, and dTMP) on TiO2 particle surfaces as a function of pH and in the presence of complementary and noncomplementary base pairs. Using attenuated total reflectance-Fourier transform infrared spectroscopy, there is an increased number of adsorbed nucleotides at lower pH with a preferential interaction of the phosphate group with the oxide surface. Additionally, differential adsorption behavior is seen where purine nucleotides are preferentially adsorbed, with higher surface saturation coverage, over their pyrimidine derivatives. These differences may be a result of intermolecular interactions between coadsorbed nucleotides. When the TiO2 surface was exposed to two-component solutions of nucleotides, there was preferential adsorption of dGMP compared to dCMP and dTMP, and dAMP compared to dTMP and dCMP. Complementary nucleotide base pairs showed hydrogen-bond interactions between a strongly adsorbed purine nucleotide layer and a weaker interacting hydrogen-bonded pyrimidine second layer. Noncomplementary base pairs did not form a second layer. These results highlight several important findings: (i) there is differential adsorption of nucleotides; (ii) complementary coadsorbed nucleotides show base pairing with a second layer, and the stability depends on the strength of the hydrogen bonding interactions and; (iii) the first layer coverage strongly depends on pH. Overall, the importance of surface interactions in the adsorption of nucleotides and the templating of specific interactions between nucleotides are discussed.

Tristyrylphenol based surfactants as efficient dispersants of TiO2 particles in dilute and concentrated dispersions

Titanium dioxide (TiO2) is widely used as a pigment in the formulation of paints. Due to the high content of TiO2 particles in the formulations, dispersants are required to avoid their aggregation. This study presents two bulky surfactants, namely, tristyrylphenol ethoxylate (TSEO, uncharged) and tristyrylphenol ethoxylate phosphate (TSEO-P, negatively charged), for the stabilization of commercial TiO2 particles at pH 8.0 (close to that used in the formulation of paints). X-ray photoelectron spectroscopy (XPS) revealed the presence of Ti, Al, Si, O and C on the surface of the commercial TiO2 particles. Batch adsorption experiments performed in the dilute range (1.0 wt%) indicated that the negatively charged TSEO-P adsorbed more efficiently on TiO2 particles (338 mg/g) than the TSEO surfactant did (qe = 222 mg/g), increasing the ζ-potential of TiO2 particles from – 24.4 ± 1.0 mV to – 39.1 ± 1.6 mV. Hydrophobic interaction between the hydrophobic tristyryl group and the organic molecules on the surface of the TiO2 particles favored the exposition of the phosphate groups to the medium. H bond between phosphate (HPO3-) and hydroxyl groups on the surface exposed the tristyryl groups to the aqueous medium, which could interact with other surfactant molecules by π-π interactions. Such structuring of surfactant (at 2.0 wt%) molecules on the TiO2 particles provided colloidal stability for TiO2 particles in the slurries (70 wt%) over 30 days at 25 °C and 52 °C, which was comparable to that provided by sodium polyacrylate (PAS, at 1.0 or 2.0 wt%). The flat paint film formulated with TSEO-P (2.0 wt%) presented a contact angle of 58.5 ± 1.0°, and superior wet scrub and leaching resistance in comparison to those prepared with sodium polyacrylate (2.0 wt%), which presented a contact angle of 52.8 ± 0.8°.

Determination of the roles of FeIII in the interface between titanium dioxide and montmorillonite in FeIII-doped montmorillonite/titanium dioxide composites as photocatalysts

Fe/Mt./TiO2 with FeIII cation doped on montmorillonite (Mt) and, Mt./Fe-TiO2 with FeIII cation doped on TiO2 were synthesized at three temperatures. Compared with the influence from the position of FeIII, the synthesis temperature had moderate interference on the TiO2 formation as was implied by X-ray fluorescence (XRF) and X-ray diffraction (XRD). Characterizations of diffuse reflectance UV–vis spectroscopy (DRS), photoluminescence spectroscopy (PL), photocurrent, and electrochemical impedance spectroscopy (EIS) indicated the more excellent photocatalytic property of Fe/Mt./TiO2 composite than Mt./Fe-TiO2 composite. The energy-resolved distribution of electron traps (ERDT) pattern revealed a distinguished phase composing from the surface to the bulk for both Fe/Mt./TiO2 and Mt./Fe-TiO2 and demonstrated almost the same photocatalytic property of the TiO2 particle surface on both Fe/Mt./TiO2 and Mt./Fe-TiO2. The photocatalytic activities test for phenol decomposition on Fe/Mt./TiO2 was better than Mt./Fe-TiO2 which is consistent with the DRS, PL, photocurrent, and EIS results. A heterojunction between the Mt. and TiO2 in Fe/Mt./TiO2 was proposed to explain the inconsistency of the photocatalytic property and photocatalytic performance for the two composites and the consistency of the photocatalytic property for the surface of TiO2 particles on the composites. To increase the photocatalytic activity of Fe/Mt./TiO2, the electron at the Fermi level on FeIII-doped Mt. may be coupled with the hole on the valance band of TiO2, resulting in effective separation of electron and hole and reduction and/or avoidance of recombination.

A novel route to the synthesis of α-Fe2O3@C@SiO2/TiO2 nanocomposite from the metal-organic framework as a photocatalyst for water treatment

In this study, an attempt was made to synthesize metal-organic frameworks (MOFs) based magnetic iron particles as photocatalysts for textile dye wastewater. Improvement strategy was a novel two-step dry method without using conventional methods to eliminate the consumption of chemical reagents. First, the heterogeneous photocatalyst of Fe-MOFs derived magnetic carbon nanocomposite with carboxylic acid surface functional groups (Fe@C–COOH) was achieved. Next, the α-Fe2O3@C@SiO2/TiO2 was successfully synthesized followed by a sol-gel method to coat the SiO2 shell and a solvothermal method to coat the surface of the intermediate TiO2 particles. The as-synthesized nanocomposite materials were characterized and physicochemical analytical equipment. Further, the investigation on magnetic photocatalytic nanocomposite α-Fe2O3@C@SiO2/TiO2 performance of dye degradation and photocatalytic activity on Reactive yellow 145 (RY145), using as an indicator was conducted. The as-synthesized nanocomposite particles were characterized using X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), X-ray energy dispersive spectroscopy (EDX), and scanning electron microscopy (SEM) techniques. The structural characterization of the as-synthesized materials proved that these methods generate oxygen-containing functional groups, such as, –OH, –CO, and –COOH, which increases the polarity and hydrophilicity of the photocatalyst. The photocatalytic oxidation of RY145 dye under UVc light was discussed by the apparent first-order reaction rate and the kinetic model of the Langmuir-Hinshelwood followed a better fitting. The optimal performance of the composite is at pH = 2, 15 mg/100 mL of photocatalyst dose, 150 mg/L concentration of the dye RY145 at 25 °C temperature under UVc lamp irradiation for 90 min, and with the apparent reaction rate constant was 0.0165 min−1. The thermodynamic analysis of activation parameters computed by the Eyring model and based on transition state theory (TST), an endothermic reaction with a positive value for Δ‡Ho (50.16 kJ mol−1) and a negative value for Δ‡So (−153 J/mol K) both contribute toward achieving positive values for Δ‡Go and a nonspontaneous process. The proposed α-Fe2O3@C@SiO2/TiO2 demonstrated a high capability of photocatalytic degradation up to 97% after five successive cycles at the optimal condition compared to that of Fe3O4@C (18.74%) and Fe@C–COOH (77.9%) without reusability.

TiO2 treatment using ultrasonication for bubble cavitation generation and efficiency assessment of a dye-sensitized solar cell

In this study, the impacts of different ultrasonic treatments on TiO2 particles were determined and they were used to manufacture the photoelectrodes of a dye-sensitized solar cell (DSSC). Two methods were used to prepare TiO2 particles directly sonicated by an ultrasonic horn, and TiO2 treated indirectly by an ultrasonic cleaner. TEM, XPS analysis was confirmed that cavitation bubbles generated during ultrasonication resulted in defects on the surface of TiO2 particles, and the defect induced surface activation. To understand the effect of TiO2 surface activation on energy conversion efficiency of DSSC, ultrasonic horn DSSC and ultrasonic cleaner DSSC were prepared. The UV–vis analysis exhibited that the ultrasonic horn DSSC possessed higher dye adsorption when compared to the ultrasonic cleaner DSSC, and the EIS analysis confirmed that the electron mobility was greatly increased in the ultrasonic horn DSSC. The energy conversion efficiency of the ultrasonic horn DSSC was measured to be 3.35%, which is about 45% increase in comparison to that of the non-ultrasonic treated DSSC (2.35%). In addition to this regard, recombination resistance of ultrasonic horn DSSC was calculated to be 450 Ω·cm2, increasing more than two times compared to the non-ultrasonic treated DSSC (200 Ω·cm2). Taken together, these ultrasonic treatments significantly improved the energy conversion efficiency of DSSC, which was not tried in DSSC-related research, and might lead us to develop more efficient practical route in the manufacturing of DSSC.

Preparation, characterization and photocatalytic performance of K8[Fe(H2O)W11MnO39]/PANI/TiO2 ternary composite

AbstractA new ternary composite catalyst, K8[Fe(H2O)W11MnO39]/PANI/TiO2, was synthesized by electrostatic self‐assembly method, of which K8[Fe(H2O)W11MnO39] was prepared by direct synthesis method, and PANI/TiO2 was prepared by coating polyaniline on the surface of TiO2 particles using chemical oxidation method with (NH4)2S2O8 as oxidant. Then, this ternary composite material was characterized by infrared (IR) spectroscopy, ultraviolet‐visible spectroscopy, X‐ray diffraction, scanning electron microscopy and N2 adsorption‐desorption, and its photocatalytic performance was explored through degradation experiments with gentian violet as an organic pollutant. The results showed that K8[Fe(H2O)W11MnO39]/PANI/TiO2 was successfully synthesized and its Keggin structure still remained with good stability. Under the optimal photocatalytic conditions, the decolorization rate of gentian violet by the ternary composite catalyst could reach to 92.93 %. After being recycled three times, the new composite catalyst still maintains good catalytic activity, indicating that it has a strong ability and reusability to degrade gentian violet with an excellent research potential.

CoS@TiO2 S-scheme heterojunction photocatalyst for hydrogen production from photoinduced water splitting

To synthesize durable catalysts, cobalt sulfide (CoS) microsheet particles are woven into a polyhedral cage shape to prevent dissolution and light corrosion during photochemical reactions. Titanium dioxide (TiO2) nanoparticles with excellent stability against water and light are used to enclose the cage. The surface of the dodecahedral CoS particle is positively charged, and the surface of the spherical TiO2 particles is negatively charged, resulting in a core–shell shaped xCoS@yTiO2 heterojunction particle. The xCoS@yTiO2 heterojunction catalyst has a stronger ability to absorb visible light and greater photocatalytic hydrogen evolution activity than pure TiO2 or CoS catalysts: When lactic acid is used as an electronic sacrificial agent, the hydrogen production of 1CoS@2TiO2 reaches 1945 μmol g−1 for 10 h, and the catalytic activities are 114.4 and 13.2 times those of CoS and TiO2, respectively. Spin-trapping ESR results reveal that charge transfer in the core–shell shaped xCoS@yTiO2 heterojunction follows the S-scheme mechanism. The excellent catalytic activity of the core–shell shaped xCoS@yTiO2 heterojunction catalyst is because of its favorable bandgap location for water splitting, higher photocurrent density, lower photoluminescence, and having strong redox sites. These factors ultimately delay the recombination of photo-induced electron/hole pairs and, as a result, high catalytic efficiency is stably maintained up to the fifth recycling test.

Effects of Cu doping on the phase transition and photocatalytic activity of anatase/rutile mixed crystal TiO2 nanocomposites

Pure and Cu doped anatase/rutile mixed TiO2 nanomaterials were fabricated through sol-gel method. The obtained photocatalysts were characterized by XRD, SEM, TEM, XPS, PL and DRS, and the influences of Cu doping on the structure and photocatalytic property were studied. The results show that when the molar ratios of Cu/Ti are 1% and 2%, Cu doping promotes anatase → rutile phase transformation. When the molar ratio of Cu/Ti is 4%, the phase transformation is inhibited. Cu element coexists in the form of Cu+ and Cu2+, and Cu doping facilitates the separation of photogenerated electrons and holes. TEM image shows that copper oxides are dispersed on TiO2 particles surface, which significantly reduces the optical absorption of ultraviolet region. The photocatalytic experiment results show that the photocatalytic activity of Cu–TiO2 is lower than pure TiO2, and the higher doping concentration, the lower photocatalytic activity.