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The photocatalytic activity of TiO 2 is correlated with its exposed crystal surface, phase composition, morphology, and crystallite size. In this study, TiO 2 microspheres with exposed crystal surface-controlled rutile TiO 2 nanorods were fabricated by employing a simple hydrothermal reaction in the presence of NaCl solution. The crystal phase, morphology, and size of the as-obtained materials were significantly dependent on the NaCl concentration. The exposed crystal surface of TiO 2 nanorods could be tailored by adjusting the NaCl concentration. With increasing NaCl concentration, the exposed area of the (1 1 1) crystal surface gradually decreased, whereas the area of the newly exposed (0 0 1) surface gradually increased. Characterization results indicated that the crystal phase of the TiO 2 microspheres was the only rutile structure in the system and no brookite phase was found. The diameter of the microspheres can be changed from 3.5 μm to 2 μm by tuning the NaCl concentration. Photocatalytic degradation of papermaking wastewater using the synthesized materials showed that the photocatalytic activities of the samples are affected by the exposed (0 0 1) crystal surface of TiO 2 , which can induce the separation of electrons and holes, thereby resulting in improved photocatalytic activity. [ABSTRACT FROM AUTHOR]

Abstract: Spherical mesoporous TiO2 particles were prepared by a facile hydrothermal treatment using titanium oxysulfate (TiOSO4) with sodium dodecyl sulfate (SDS) as the structure-directing agent. The structure and morphology of the as-prepared TiO2 particles were characterized by X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, and N2 adsorption–desorption isotherms. The results indicate that the as-synthesized TiO2 particles have spherical mesoporous structures. Moreover, the crystal phase of the particles was the only anatase structure. This finding was attributed to the presence of sulfate ion (SO4 2−), which inhibited the anatase–rutile phase transformation and improved the crystallinity of TiO2 during TiOSO4 hydrolysis. The spherical mesoporous TiO2 materials have very high surface areas, and the mesopores have narrow pore size distributions. In the degradation of papermaking wastewater under ultraviolet light irradiation, the prepared TiO2 particles exhibited high photocatalytic activity compared with the commercial Degussa P25. The effects of various parameters such as catalyst dosage, solution pH, and irradiation time on the photocatalytic activity of the fabricated TiO2 powders are discussed. At the optimum dose of 1.0gL−1 TiO2 at pH4, the particles prepared using an SDS:TiOSO4 molar ratio of 0.6 exhibited the highest photocatalytic activity, achieving 83.6% CODCr removal rate in 12h and 100% chroma removal rate in 8h. [Copyright &y& Elsevier]

Highlights: [•] Large-diameter tube-like mesoporous TiO2 was synthesized using CTAB and urea. [•] A possible mechanism for the formation of tube-like mesoporous TiO2 was proposed. [•] Tube-like TiO2 was suitable for photodegradation of papermaking wastewater. [•] Tube-like TiO2 showed much higher photocatalytic activities than Degussa P25. [ABSTRACT FROM AUTHOR]

Nitrogen-modified cobalt-doped TiO materials were successfully prepared via a modified sol-gel method. The structure and properties of the catalysts were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM, ultraviolet-visible light diffuse reflectance spectra (UV-Vis DRS), N adsorption-desorption isotherms, and energy-dispersive X-ray spectroscopy. The XRD patterns of the pure and co-doped TiO samples indicate that the predominant phase was anatase. The average grain size obtained from TEM was approximately 10 nm. The Brunauer-Emmett-Teller analysis results indicate that the specific surface area was 77.7 m g. The UV-Vis DRS results for the co-doped sample reveal an absorption edge that had been red-shifted to 500 nm. The photocatalytic activities of the samples were evaluated through photodegradation of papermaking wastewater under UV and visible light irradiation. Compared with the cobalt-doped TiO sample and Degussa P25, the 3 mol% N-doped mesoporous N/Co-TiO photocatalyst exhibited the highest photocatalytic activity, which can be ascribed to the synergistic effect of the N and Co co-doping. [ABSTRACT FROM AUTHOR]

Abstract: Using composite surfactant templates, polyoxyethylene (20) oleyl ether (Brij98) and cetyl trimethyl ammonium bromide (CTAB), as structure-directing agents, N and La co-doped mesoporous TiO2 complex photocatalysts were synthesized successfully. The micromorphology of co-doped mesoporous TiO2 samples was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FT-IR), energy-dispersive X-ray spectrometer (EDS) and N2 adsorption–desorption measurements. The results indicated that the complex photocatalyst prepared with a molar ratio of Brij98:CTAB=1:1 showed a uniform pore size of ca. 7nm and a high specific surface area (S BET) of 279.0m2 g−1, and exhibited the highest photocatalytic activity for degradation of papermaking wastewater under ultra-violet light irradiation. The chemical oxygen demand (CODcr) percent degradation was about 73% in 12h and chroma percent degradation was 100% in 8h. [Copyright &y& Elsevier]

Abstract: Using Tween 80 as pore-directing agent, mesoporous TiO2− x N x was prepared via the hydrolysis of TTIP (titanium tetraisopropoxide) in a mixed aqueous solution of isopropanol and acetic acid in the presence of urea. The resulting mesoporous TiO2− x N x was characterized by XRD, N2 adsorption–desorption isotherms, TEM, UV–vis diffuse reflectance spectra and EDS. TEM and N2 adsorption–desorption isotherms showed that the TiO2− x N x has a uniform mesoporous structure. UV–vis spectra revealed that the nitrogen doping caused the absorption edge of TiO2− x N x to shift to the visible region. 10%N–TiO2 exhibited the highest photocatalytic activity for degradation of MO aqueous solution under solar simulated light irradiation. [Copyright &y& Elsevier]

• An emerging Ti 3 C 2 MXene cocatalyst bridged Ag/Ag 3 PO 4 hybrids were synthesized. • The hybrids exhibited superior visible-light-driven photocatalytic activity. • Ti 3 C 2 MXene promoted separation and transfer of photogenerated electron-hole pairs. • The synergistic effect of Ag, Ag 3 PO 4 , and Ti 3 C 2 contributed to the high activity. As a novel transition metal carbides and/or carbonitrides, MXene possess two-dimensional characteristic, abundant surface hydrophilic functional groups, and excellent electrical conductivity that bestow a possibility to building MXene-based photocatalysts. Inspired by this, an emerging Ti 3 C 2 MXene cocatalyst bridged Ag/Ag 3 PO 4 to induce a highly visible-light-driven photocatalytic activity, synthesized by electrostatic self-assembly method and the partial reduction of Ag+ ions to Ag0 in MXene solution is reported. The resultant hybrids reveal a well-defined hybrid structures with Ag/Ag 3 PO 4 anchoring on the layer structured Ti 3 C 2 nanosheets. Benefiting from the unique structural features, the Ag/Ag 3 PO 4 /Ti 3 C 2 hybrids present Ti 3 C 2 content-dependent photocatalytic activity toward the methyl orange (MO) degradation and Cr(VI) reduction under visible-light irradiation. Remarkably, the Ag/Ag 3 PO 4 /Ti 3 C 2 hybrid with 3 wt% Ti 3 C 2 content achieves the greatest MO degradation efficiency and Cr(VI) reduction efficiency after irradiation for 1 h, which are increased to 1.72 and 1.46 times higher than that obtained on pristine Ag 3 PO 4 nanoparticles, respectively. Such impressive photocatalytic activity is related to the synergeric effects derived from Ag, Ag 3 PO 4 , and Ti 3 C 2 , which greatly enhance visible light absorption, promote separation and transfer of photo-generated electron-hole pairs. This work highlights that the MXene-based photocatalysts would be desirable candidates for environmental purification of organic pollutants and heavy metal ions. [ABSTRACT FROM AUTHOR]

• Step scheme (S-scheme) heterojunction is one of the newly effective approaches to promote the photocatalytic performance of coupled semiconductors. • 2D/2D In 2 S 3 /Bi 2 O 2 CO 3 S-scheme heterojunction photocatalyst was designed and fabricated. • The internal electric field of S-scheme heterojunction not only efficiently restrain the recombination of photogenerated charges but also enlarge the redox capability of the 2D/2D In 2 S 3 /Bi 2 O 2 CO 3. • The designed S-scheme heterojunction showed very enhanced photocatalytic degradation towards RhB and tetracycline (TC). To fabricate step scheme (S-scheme) heterojunction is one of the newly effective approaches to promote the photocatalytic performance of coupled semiconductors. Herein, a two-dimension (2D)/2D In 2 S 3 /Bi 2 O 2 CO 3 S-scheme heterojunction photocatalyst was designed and fabricated through a facile two-step precipitation method. The as-synthetized composite presented in face-to-face hierarchical structure with enhanced photocatalytic performance towards the degradation of Rhodamine B (RhB) and tetracycline (TC) under light irradiation. The 2D/2D In 2 S 3 /Bi 2 O 2 CO 3 heterojunction not only enlarges the light utilization region but also effectively restrains the recombination of useful photogenerated electron-hole pairs, which was demonstrated by diffuse reflection spectra (DRS), photoluminescence spectra (PLS) and active species trapping experiments. Particularly, the optimal performance was achieved using 10% In 2 S 3 /Bi 2 O 2 CO 3 heterojunction with 91% degradation capacity towards RhB in 60 min, which was about 5 and 3 times higher than that of pure Bi 2 O 2 CO 3 and In 2 S 3 , respectively. Moreover, the cycling performance of the photocatalysts further confirmed the excellent stability of the heterojunction. Based upon the characterization and experimental results, the mechanism of S-scheme heterojunction was employed to illustrate the effectively enhanced photocatalytic performance of the 2D/2D In 2 S 3 /Bi 2 O 2 CO 3 heterojunction. [ABSTRACT FROM AUTHOR]