Using TiO<Subscript>2</Subscript> supported on Clinoptilolite as a catalyst for photocatalytic degradation of azo dye Disperse yellow 23 in water

In this investigation photocatalytic degradation of azo dye Disperse yellow 23 in water was studied. Titanium (IV) oxide was supported on Clinoptilolite (CP) (Iranian Natural Zeolite) using the solid-state dispersion (SSD) method. The results show that the TiO₂/Clinoptilolite (SSD) is an active photocatalyst. The maximum effect of photo degradation was observed at 10 wt % TiO₂, 90 wt % Clinoptilolite. A first order reaction with k = 0.0119 min^?1 was observed. The effects of some parameters such as pH, amount of photocatalyst, and the initial concentration of dye were examined.     

Synthesis,characterization and photocatalytic application of TiO2/magnetic graphene for efficient photodegradation of crystal violet

A magnetized nano‐photocatalyst based on TiO₂/magnetic graphene was developed for efficient photodegradation of crystal violet (CV). Scanning electron microscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy and elemental mapping were used to characterize the prepared magnetic nano‐photocatalyst. The photocatalytic activity of the synthesized magnetic nano‐photocatalyst was evaluated using the decomposition of CV as a model organic pollutant under UV light irradiation. The obtained results showed that TiO₂/magnetic graphene exhibited much higher photocatalytic performance than bare TiO₂. Incorporation of graphene enhanced the activity of the prepared magnetic nano‐photocatalyst. TiO₂/magnetic graphene can be easily separated from an aqueous solution by applying an external magnetic field. Effects of pH, magnetized nano‐photocatalyst dosage, UV light irradiation time, H₂O₂ amount and initial concentration of dye on the photodegradation efficiency were evaluated and optimized. Efficient photodegradation (>98%) of the selected dye under optimized conditions using the synthesized nano‐photocatalyst under UV light irradiation was achieved in 25 min. The prepared magnetic nano‐photocatalyst can be used in a wide pH range (4–10) for degradation of CV. The effects of scavengers, namely methanol (OH^? scavenger), p‐benzoquinone (O₂^?? scavenger) and disodium ethylenediaminetetraacetate (hole scavenger), on CV photodegradation were investigated.     

Photodegradation of Rhodamine B on Sulfur Doped ZnO/TiO2 Nanocomposite Photocatalyst under Visible-light Irradiation

Sulfur doped ZnO/TiO₂ nanocomposite photocatalysts were synthesized by a facile sol‐gel method. The structure and properties of catalysts were characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), UV‐vis diffusive reflectance spectroscopy (DRS) and N₂ desorption‐adsorption isotherm. The XRD study showed that TiO₂ was anatase phase and there was no obvious difference in crystal composition of various S‐ZnO/TiO₂. The XPS study showed that the Zn element exists as ZnO and S atoms form SO^2?₄. The prepared samples had mesoporosity revealed by N₂ desorption‐adsorption isotherm result. The degradation of Rhodamine B dye under visible light irradiation was chosen as probe reaction to evaluate the photocatalytic activity of the ZnO/TiO₂ nanocomposite. The commercial TiO₂ photocatalyst (Degussa P25) was taken as standard photocatalyst to contrast the prepared different photocatalyst in current work. The improvement of the photocatalytic activity of S‐ZnO/TiO₂ composite photocatalyst can be attributed to the suitable energetic positions between ZnO and TiO₂, the acidity site caused by sulfur doping and the enlargement of the specific area. S‐3.0ZnO/TiO₂ exhibited the highest photocatalytic activity under visible light irradiation after Zn amount was optimized, which was 2.6 times higher than P25.     

Photocatalytic activity of polyaniline/Fe-doped TiO2 composites by in situ polymerization method

This study was focused on the photocatalytic activity of polyaniline (Pani)/iron doped titanium dioxide (Fe–TiO₂) composites for the degradation of methylene blue as a model dye. TiO₂ nanoparticles were doped with iron ions (Fe) using the wet impregnation method and the doped nanoparticles were further combined with Pani via an in situ polymerization method. For comparison purposes, Pani composites were also synthesized in the presence undoped TiO₂. The photocatalyst and the composites were characterized by standard analytical techniques such as FTIR, XRD, SEM, EDX and UV–Vis spectroscopies. Fe–TiO₂ and its composites exhibited enhanced photocatalytic activity under ultraviolet light irradiation. Improved photocatalytic activity of Fe–TiO₂ was attributed to the dopant Fe ions hindering the recombination of the photoinduced charge carriers. Pani/Fe–TiO₂ composite with 30?wt.% of TiO₂ nanoparticles achieved 28% dye removal and the discoloration rate of methylene blue for the sample was 0.0025?min^?1. FTIR, XRD, SEM, EDX and UV–Vis spectroscopies supported the idea that Fe ions integrated into TiO₂ crystal structure and Pani composites were successfully synthesized in the presence of the photocatalyst nanoparticles. The novelty of this study was to investigate the photocatalytic activity of Pani composites, containing iron doped TiO₂ and to compare their results with that of Pani/TiO₂.     

Improving the Photocatalytic Activity of Modified Anatase TiO2 with Different Concentrations of Aluminum under Visible Light: Mechanistic Survey

Visible light‐driven Al‐doped TiO₂ with different aluminum contents (2, 5 and 10 mol%) were synthesized via a facile sol–gel method. Fourier transform infrared (FTIR), UV‐visible diffuse reflectance, energy dispersive X‐ray (EDX) spectroscopy as well as X‐ray diffraction (XRD), X‐ray fluorescence (XRF) and scanning electron microscopy (SEM) methods were used for the characterization of the obtained nanoparticles. The photocatalytic performance of the samples was evaluated by the degradation of rhodamine B (RhB) under visible light irradiation. The yield of the degradation RhB was estimated to be 71%, 89%, 65% and 56%, for the bare TiO₂, 2%, 5% and 10% Al‐doped TiO₂, respectively. It was found that 2 mol% of Al‐doped TiO₂ shows the best photocatalytic performance. In low concentration of dopant, separation of photogenerated electron–hole pairs promoted, and subsequently, the degradation efficiency increased. It was proposed that the degradation of RhB by 2 mol% Al‐doped TiO₂ photocatalyst follows both N‐deethylation and chromophore cleavage mechanisms, while the N‐deethylation still predominated over cleavage of dye chromophore structure. The key role of hydroxyl radicals in RhB degradation was verified by the effects of scavengers. In addition, the photocatalyst can be reused for three runs without any significant loss of its catalytic activity.     

Multifunctional Zn0.3Al0.4O4.5 crystals: An efficient photocatalyst for formaldehyde degradation and EBT adsorption

The Zn_0.3Al_0.4O_4.5 nanoparticles (ZnAlONPs) with size of 70–90 nm are used as an efficient photocatalyst for formaldehyde (HCHO) degradation and effective adsorbent for the removal of eriochrome black-T (EBT) dye from synthetic aqueous solution. Degradation of HCHO reactions were studied using TiO₂ (homemade), TiO₂ (P-25) and ZnAlONPs by irradiating under 18 W daylight lamp source for photocatalytic degradation. The HCHO degradation rate is about 67, 76 and 89% for TiO₂ (homemade), TiO₂ (P25) and ZnAlONPs during 2 h reaction, respectively at initial formaldehyde gas concentration of 20 ppm. Maximum adsorption capacity was optimized by changing the parameters such as pH, EBT concentration and adsorbent dosage. A  200 mg of ZnAlONPs are useable for quick removal of EBT (>95%). Langmuir isotherm model showed a maximum adsorption capacity of 90.90 mgg⁻¹. The ZnAlONPs could be successfully reused upto 5^th adsorption/desorption cycle for EBT dye removal from water samples.     

Enhancing photocatalytic activity of titanium dioxide through incorporation of MIL‐53(Fe) toward degradation of organic dye

Photocatalytic activity of titanium(IV) oxide (TiO₂) can be enhanced through modification of its surface‐active sites. Here, iron(III) carboxylate [MIL‐53[Fe]]‐incorporated TiO₂ (as MIL‐53(Fe)/TiO₂) was prepared using a hydrothermal method. This material was then calcined at 500°C to obtain a MIL‐53(Fe)‐derived γ‐Fe₂O₃/TiO₂ photocatalyst. A photocatalytic study of MIL‐53(Fe)/TiO₂ and MIL‐53(Fe)‐derived γ‐Fe₂O₃/TiO₂ toward cationic methylene blue (MB) and anionic methyl orange (MO) showed that MIL‐53(Fe)/TiO₂ (0.25 wt%) and MIL‐53(Fe)‐derived γ‐Fe₂O₃/TiO₂ (0.75 wt%) resulted the best degree of dye degradation. The MIL‐53(Fe)‐derived γ‐Fe₂O₃/TiO₂ (0.75 wt%) composite for instance is capable of degrading almost 100% of 20‐ppm MB and MO, respectively, within 6 hr. Photocatalytic degradation of MB and MO was well fitted to the Langmuir‐Hinshelwood pseudo‐first order kinetics model, which indicates physisorption as the key partway that facilitates dye decomposition on the surface of a photocatalyst under UV‐A irradiation. This study provides new insights into the exploration of MILs/TiO₂ materials for the environmental remediation and pollution control.     

Preparation of Pt@SnO2 Core‐Shell Nanoparticles for Photocatalytic Degradation of Formaldehyde

We report the synthesis and characterization of platinum‐tin oxide core‐shell nanoparticles (Pt@SnO₂) for use as a photocatalyst for formaldehyde (HCHO) degradation. We used a sol‐gel process followed by calcination to prepare the Pt@SnO₂ photocatalyst. Transmission Electron Microscopy (TEM) revealed that the average Pt core diameter was 7‐10 nm in diameter, and the SnO₂ shell was approximately 2 nm thick. UV‐Visible spectroscopy displayed the peak from the Pt@SnO₂ core‐shell structures is red‐shifted by 16 nm from that of the Pt nanoparticles. We determined photocatalytic activity by irradiating formaldehyde gas in the presence of nanoparticle samples with an 18 W daylight lamp for 180 min. The irradiated Pt@SnO₂ nanoparticles achieved 93.2% formaldehyde degradation, while TiO₂ (P25), SnO₂, and 1 wt.% Pt/SnO₂ achieved 70.1%, 67.5%, and 66.0% respectively. Thus, Pt@SnO₂ was the most effective material for the degradation of formaldehyde, demonstrating its potential for use as a high efficiency photocatalyst for the degradation of formaldehyde.     

The Properties and Activity of TiO2/beta‐SiC Nanocomposites in Organic Dyes Photodegradation

The TiO₂/beta‐SiC nanocomposites containing 0–25 wt. % of beta‐SiC were synthesized by the sol‐gel method and tested in the photodegradation of methylene blue and methyl orange water solutions. With the increase in SiC content, only a slight decrease in energy band gap was observed (3.19–3.12 eV), together with significant increase in the surface area of the catalysts (42.7–80.4 m² g^?1). In the synthesized material, the anatase phase of TiO₂ was present in the form of small agglomerates resulting from the mechanical mixing process. In the process conditions (catalyst concentration 0.5 g L^?1, initial dye concentration 100 ppm, light source 100 W UV‐Vis lamp), we have observed no signs of catalyst deactivation. The significantly higher photodegradation activity of methylene blue than methyl orange can be attributed to the preferable pH of the solution compared to pH_PZC and the cationic character of the first dye. In case of methyl orange, pH process conditions substantially limit the contact of the catalyst with the dye, as negatively charged surface of the catalysts repels the dissociated anionic dye molecules.     

High-power ultrasonic-assisted phenol and dye degradation on porous manganese oxide doped titanium dioxide catalysts

In this study, a high-power ultrasonicator (600 W) is employed to examine dye degradation and phenol decomposition efficiencies in the presence of catalysts such as K-OMS-2, TiO₂, K-OL-1 doped TiO₂ and K-OMS-2 doped TiO₂. Methylene blue and phenol are chosen as the model pollutants to test the catalytic activity. Effects of ultrasonic power level or ultrasonic intensity, amount of catalysts used and ultrasonic irradiation time for catalytic degradation and removal of phenol were studied. No d-spacing peak shift was observed in intense XRD peaks of K-OMS-2- and K-OL-1-doped TiO₂ materials when compared with commercial TiO₂. Scanning and transmission electron micrographs (SEM and TEM) show aggregated particle morphology with spherical and rectangular particles for 5 wt % K-OMS-2/TiO₂. Methylene blue dye degradation efficiency in the presence of catalytic ultrasonication follows the order like TiO₂ > 5 wt % K-OMS-2/TiO₂ > 5 wt % K-OL-1/TiO₂. The K-OMS-2- and 5 wt % K-OMS-2-doped TiO₂ catalyst showed the best and most promising efficiency for phenol removal in ultrasonication process. K-OMS-2 shows the best phenol removal efficiency of 58% within a short duration (30 min) of catalytic ultrasonic-assisted reaction.     

Construction of a TiO2–Fe3O4‐decorated molecularly imprinted polymer nanocomposite for tartrazine degradation: Response surface methodology modeling and optimization

We synthesized a novel recoverable and reusable photocatalyst system for tartrazine degradation by one‐step incorporation of Fe₃O₄ and TiO₂ nanoparticles into a molecularly imprinted polymer through a facile precipitation polymerization method. The as‐prepared samples were systematically characterized using X‐ray diffraction, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy‐dispersive spectroscopy, and vibrating sample magnetometry. Benefiting from the positive synergistic effect, tartrazine was almost completely degraded under UV‐C within 180 min by the multicomponent photocatalyst (Fe₃O₄ + TiO₂ + MIP) in comparison with far fewer activities by the corresponding NIP system and the nonmagnetic and bare structures. On the other hand, the central composite design in response surface methodology was applied to optimize the tartrazine photocatalytic degradation process. Twenty experiments were conducted by adjusting three parameters (nanocomposite dosage, initial pH of the reaction solution, and initial dye concentration) in the multiple variable analysis method. A satisfactory correlation between the experimental and predicted values was obtained (R² = 0.956). Additionally, ANOVA analysis with a p value of 1.15 × 10^–5 indicated that the model terms are highly significant. Under the determined optimum conditions, a verification experiment was conducted and shown the adequately approximate value between the predicted (99%) and the experimental (97%) results, which confirmed the validity of the model.     

A Novel Composite Electrode of Photocatalyst—TiO2／C Loading on the Surface of the Air （Oxygen） Electrode

The methods for preparing the H2O2 generating air (oxygen) electrode and the composite electrode of photocatalyst-TiO2/C loading on the surface of the air (oxygen) electrode were introduced.In the case of the composite electrode,the current efficiency of electro-generated H2O2 is higher than 80%(J≤15mA/cm^2).The degradation of aniline was used as an example to measure the influence of the composite electrode and compared with the system in which the air (oxygen) electrode and the photocatalyst-TiO2 were sqparated.The results confirmed that the composite electrode played an active role on accelerating the degradation rate of aniline.According to the measurement of the polarization curves of composite electrode and TiO2 photo anode,and of the adsorbing amount of aniline on the surface of the composite electrode,the principle of descending the recombination reta of photo-generated electron and hole and of enhancing the oxidation rate of organic molecule was described.The mechanism about the degradation of aniline was also discussed.     

CdS‐Encapsulated TiO2 Nanotube Arrays Lidded with ZnO Nanorod Layers and Their Photoelectrocatalytic Applications

A novel TiO₂ nanotube array/CdS nanoparticle/ZnO nanorod (TiO₂ NT/CdS/ZnO NR) photocatalyst was constructed which exhibited a wide‐absorption (200–535 nm) response in the UV/Vis region and was applied for the photoelectrocatalytic (PEC) degradation of dye wastewater. This was achieved by chemically assembling CdS into the TiO₂ NTs and then constructing a ZnO NR layer on the TiO₂ NT/CdS surface. Scanning electron microscopy (SEM) results showed that a new structure had been obtained. The TiO₂ NTs looked like many “empty bottles” and the ZnO NR layer served as a big lid. Meanwhile the CdS NPs were encapsulated between them with good protection. After being sensitized by the CdS NPs, the absorption‐band edge of the obtained photocatalyst was obviously red‐shifted to the visible region, and the band gap was reduced from its original 3.20 eV to 2.32 eV. Photoelectric‐property tests indicated that the TiO₂ NT/CdS/ZnO NR material maintained a very high PEC activity in both the ultraviolet (UV) and the visible region. The maximum photoelectric conversion efficiencies of TiO₂ NT/CdS/ZnO NR were 31.8 and 5.98 % under UV light (365 nm) and visible light (420–800 nm), respectively. In the PEC oxidation, TiO₂ NT/CdS/ZnO NR exhibited a higher removal ability for methyl orange (MO) and a high stability. The kinetic constants were 1.77×10^?4 s^?1 under UV light, which was almost 5.9 and 2.6 times of those on pure TiO₂ NTs and TiO₂ NT/ZnO NR, and 2.5×10^?4 s^?1 under visible light, 2.4 times those on TiO₂ NT/CdS.     

Photo Catalytic Degradation of Azo Dyes over Mn2+ Doped TiO2 Catalyst under UV/Solar Light:An Insight to the Route of Electron Transfer in the Mixed Phase of Anatase and Rutile

Mn²⁺ ion was doped into the TiO₂ matrix and its photocatalytic activity was evaluated for the degradation of a mono azo dye methyl orange (MO) and a di‐azo dye brilliant yellow (BY) under UV/solar light. X‐ray diffraction results revealed the phase transformation from anatase to rutile due to the inclusion of Mn²⁺ ion into the TiO₂ matrix. All the doped catalysts showed a red shift in the band gap to the visible region. The degradation reaction of the dyes was found to be dependent on its structure. It was found that mono azo dye degrades faster than di azo dye under UV/solar light. The rate constant under identical conditions calculated for the degradation of MO is 2.4 times (under UV light) and 4.5 times (under solar light) higher compared to BY. Among the photocatalysts studied, Mn²⁺(0.06 at.%)‐TiO₂ showed higher activity under both UV and solar light illumination. The synergestic effect in the bicrystalline framework of anatase and rutile effectively suppresses the charge carrier recombination and enhances the photocatalytic activity. The degradation reaction was followed by UV‐visible spectroscopy and the photoproducts formed were analyzed by GC‐MS techniques.     

Fabrication of nanoporous polymeric crystalline TiO2 composite for photocatalytic degradation of aqueous organic pollutants under visible light irradiation

A nanoporous polymeric crystalline TiO₂ composite (TiO₂/PDVB‐MA) has been successfully synthesized through an in situ synthesis method using divinylbenzene (DVB), methacrylic acid (MA) and tetrabutyl titanate. The experimental results showed that TiO₂ nanoparticles composed of the mixture phases of anatase and rutile were homogeneously dispersed into the PDVB‐MA support. The TiO₂/PDVB‐MA composite was used as photocatalyst for Rhodamine B (RhB), bisphenol A and 2,4,6‐trichlorophenol degradation under visible light irradiation. More interestingly, the excellent photocatalytic performance of the composite was observed with regard to RhB and bisphenol A, which might be ascribed to the synergistic effect between TiO₂ nanoparticles and PDVB‐MA. Moreover, TiO₂/PDVB‐MA composite could be recycled at least four times in the removal of RhB, suggesting that it is a promising photocatalyst to catalyze the degradation of organic pollutants under visible light irradiation.     

Hierarchical TiO2 nanosheet‐assembled nanotubes with dual electron sink functional sites for efficient photocatalytic degradation of rhodamine B

A novel Pt–TiO₂/Ag nanotube photocatalyst has been synthesized successfully via a facile method. TiO₂ nanotubes are assembled with numerous ultrathin TiO₂ nanosheets and show a highly open structure. The gaps between adjacent TiO₂ nanosheets can serve as channels for the access of reactants, accelerating the mass transfer process. During the fabrication process of the Pt–TiO₂/Ag nanotube photocatalyst, high‐quality Pt–SiO₂ nanotubes are synthesized first with the structure‐directing effect of polyvinylpyrrolidone. Then a TiO₂ layer is coated on the outside surface of the silica nanotubes. The introduced titanium species can be converted into TiO₂ nanosheet structure during the subsequent hydrothermal treatment, gradually constructing nanosheet‐assembled nanotubes. Lastly, after the introduction of another electron sink function site of Ag through UV irradiation, the Pt–TiO₂/Ag nanotube photocatalyst with dual electron sink functional sites is obtained. The specially doped Pt and Ag NPs can simultaneously inhibit the recombination process of photogenerated charge carriers and increase light utilization efficiency. Therefore, the as‐synthesized Pt–TiO₂/Ag nanotube catalyst exhibits a high photocatalytic degradation performance for rhodamine B of 0.2 min^?1, which is about 3.2 and 5.3 times as high as that of Pt–TiO₂ and TiO₂ nanotubes because of the enhanced charge carrier separation efficiency. Furthermore, in the unique nanoarchitecture, the nanotubes are assembled with numerous ultrathin TiO₂ nanosheets, which can absorb abundant active species and dye molecules for photocatalytic reaction. On the basis of experimental results, a possible rhodamine B degradation mechanism is proposed to explain the excellent photocatalytic efficiency of the Pt–TiO₂/Ag nanotube photocatalyst.     

The Role of the Relative Dye/Photocatalyst Concentration in TiO2 Assisted Photodegradation Process

Despite photocatalytic degradation is studied generally focusing the catalyst, its interaction with the contaminant molecule plays a fundamental role in the efficiency of that process. Then, we proposed a comparative study about the photodegradation of two well‐known dyes, with different acidity/basicity – Methylene Blue (MB) and Rhodamine B (RhB), catalyzed by TiO₂ nanoparticles, varying both dye and photocatalyst concentrations. The results showed that the amphoteric character of MB molecules, even in a range of concentration of 5.0–10.0 mg L^?1, did not imply in pH variation in solution. Therefore, it did not affect the colloidal behavior of TiO₂ nanoparticles, independent of the relative dye/catalyst concentration. The acid–base character of RhB influenced the resultant pH of the solution, implicating in different colloidal behavior of the nanoparticles and consequently, in different degradation conditions according to dye concentration. As the isoelectric point of TiO₂ is between the pH range of the RhB solutions used in this study, from 1.0 to 7.5 mg L^?1, the resultant pH was the key factor for degradation conditions, from a well dispersed to an agglomerated suspension.     

Photocatalytic degradation of dimethyl phthalate ester using novel hydrophobic TiO2 pillared montmorillonite photocatalyst

TiO₂ pillared montmorillonites were prepared by introducing Ti⁴⁺ into a layer of montmorillonite modified with or without cetyltrimethylammonium bromide. The components and texture of the prepared composites were characterized by thermogravimetric analysis, X-ray powder diffraction and scanning electron misroscopy. The adsorption and photocatalytic degradation performance of a model environmental endocrine disruptor, dimethyl phthalate ester, were investigated using this newly prepared hydrophobic TiO₂ pillared montmorillonite photocatalyst. The adsorption of dimethyl phthalate ester from water varied from 9% to 28% on the prepared hydrophobic photocatalyst. Although the experimental results showed that the photocatalytic activity of the hydrophobic photocatalyst was slightly lower than that of hydrophilic one, electron spin resonance verified that hydroxyl radicals were also generated in hydrophobic TiO₂ pillared montmorillonite photocatalyst under UV irradiation. To elucidate the decomposition mechanism of dimethyl phthalate ester, 12 main photocatalytic intermediates were identified during the photocatalytic degradation process, and a plausible degradation mechanism was also proposed.     

TiO2 Photocatalyzed Degradation of the Azo Dye Disperse Red 1 in Aqueous Micellar Environments†

The photoinduced degradation of the azo dye Disperse Red 1 was studied in a microheterogeneous system comprising titanium oxide (TiO₂) and sodium dodecyl sulfate, exposed to UV light. Degussa P25, Anatase and TiO₂ synthesized in acidic conditions were supported on raschig rings. The TiO₂ photocatalyzed degradation is enhanced in the vicinity of the surfactant critical micelle value. Further increase on the surfactant concentration leads to a loss in photodegradation performance up to values equivalent to that observed without surfactant. Surfactant influence can be explained by two different phenomena taking place. The increasing concentration of surfactant leads to an increase in micellar concentration, inducing the incorporation of the dye to the hydrophobic moiety of the micelles, rendering the hydroxyl radical unable to interact with the dye. Similarly, the increased concentration of micelles at the photocatalyst/water interface might lead to a decrease in the number of active sites on the TiO₂ surface able to either generate reactive species and/or interact with de dye molecules. Additives such as H₂O₂, NaCl, Na₂SO_4, and Na₂CO₃ are able to override the influence of the surfactant both positively and negatively, being the final outcome of the influence highly dependent on the crystalline form of the TiO₂ photocatalyst.     

Porous TiO2 Nanotubes with Spatially Separated Platinum and CoOx Cocatalysts Produced by Atomic Layer Deposition for Photocatalytic Hydrogen Production

Efficient separation of photogenerated electrons and holes, and associated surface reactions, is a crucial aspect of efficient semiconductor photocatalytic systems employed for photocatalytic hydrogen production. A new CoO_x/TiO₂/Pt photocatalyst produced by template‐assisted atomic layer deposition is reported for photocatalytic hydrogen production on Pt and CoO_x dual cocatalysts. Pt nanoclusters acting as electron collectors and active sites for the reduction reaction are deposited on the inner surface of porous TiO₂ nanotubes, while CoO_x nanoclusters acting as hole collectors and active sites for oxidation reaction are deposited on the outer surface of porous TiO₂ nanotubes. A CoO_x/TiO₂/Pt photocatalyst, comprising ultra‐low concentrations of noble Pt (0.046 wt %) and CoO_x (0.019 wt %) deposited simultaneously with one atomic layer deposition cycle, achieves remarkably high photocatalytic efficiency (275.9 μmol h⁻¹), which is nearly five times as high as that of pristine TiO₂ nanotubes (56.5 μmol h⁻¹). The highly dispersed Pt and CoO_x nanoclusters, porous structure of TiO₂ nanotubes with large specific surface area, and the synergetic effect of the spatially separated Pt and CoO_x dual cocatalysts contribute to the excellent photocatalytic activity.