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The photoreduction of uranium over TiO 2 provides an important pathway to uranium resource utilization and pollution abatement. However, the impact of the TiO 2 crystalline type on photocatalytic reduction of U(VI) is still unclear. In this study, the influence of crystal type of TiO 2 on U(VI) photoreduction was studied. The results showed that rutile was more reactive for the photocatalytic reduction of U(VI) than anatase. Interestingly, an obvious synergistic effect was observed for mechanically mixed rutile-anatase and the photoconverted UO 2 particles preferred to precipitate on rutile surface. The optimum efficiency was achieved for the mixture containing 30 wt% anatase and 70 wt% rutile. The anatase {101} planes tended to match up with rutile {110} facets after the two minerals were mixed. The formation of rutile-anatase aggregates led to the transfer of photogenerated electrons from anatase to rutile. This process could prolong the lifetime of carriers, facilitating U(VI) reduction. Unlabelled Image • Photocatalytic U(VI) reduction was more efficient over rutile than anatase. • Alignment was formed between mechanically mixed anatase and rutile, promoting photocatalytic U(VI) reduction. • Heterostructure was formed after anatase and rutile aggregated. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Deep gap states of TiO 2 nanorod array were identified by cyclic voltammetries. • Spatial location, energy position, and chemical entity of gap states were revealed. • High sub-band gap response was observed in photoelectrochemical water oxidation. Abstract Developing new methods to use visible light is important for TiO 2 photocatalysis. This research reported that the TiO 2 rutile nanorod (NR) array shows high sub-band gap visible light response. By means of electrochemical cyclic voltammetries, the intrinsic occupied gap states of TiO 2 NR array were identified. It was seen that the gap states can be switched from filled states to empty states by visible light illumination, which play the role of relay in promoting electrons from the valence band to the conduction band of TiO 2 NRs after absorbing two visible photons. In a consequence, the TiO 2 NR array shows the obvious anodic photocurrents for water photoelectrochemical oxidation and the photocatalytic degradation of methyl orange under visible light illumination. This study revealed the significance of the deep occupied gap states of TiO 2 NR arrays, which are usually considered as recombination centers. Different from conventional photocatalysis arising from inter-band electron transition, the present research shows a different pathway to use visible light in TiO 2 photocatalysis effectively, which should be highly meaningful for designing visibly-active TiO 2 photocatalysts. [ABSTRACT FROM AUTHOR]

In this work, we prepared a new wide band gap semiconductor, p -block metal oxyhydroxide InOOH, which exhibits efficient activity for perfluorooctanoic acid (PFOA) degradation under mild conditions and UV light irradiation. The apparent rate constant for PFOA degradation by InOOH is 27.6 times higher than that for P25 titania. Results show that ionized PFOA (C 7 F 15 COO − ) can be adsorbed much more efficiently on the surface of InOOH than P25. Then, the adsorbed C 7 F 15 COO − can be decomposed directly by photo-generated holes to form C 7 F 15 COO radicals. This process is the key step for the photocalytic degradation of PFOA. Major degradation intermediates, fluoride ions and perfluorinated carboxylic acids (PFCAs) with shorter chain lengths were detected during PFOA degradation. A possible pathway for photocatalytic degradation of PFOA is proposed based on the experimental results. Therefore, this studies indicates a potential new material and method for the efficient treatment of PFCA pollutants under mild conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The size of MTN were simply controlled. • Monodispersed Ag/bMTN were prepared by a novel in situ method. • PDA/Ag/bMTN exhibited narrowed bandgap and enhanced visible light absorption. • Photocatalytic and antibacterial mechanisms of PDA/Ag/bMTN were suggested. Driven by clean solar energy, photocatalytic technology can effectively degrade organic pollutants and kills pathogenic bacteria. Researchers are always devoted to developing more economical and efficient photocatalysts. In this work, mesoporous TiO 2 nanoparticles (MTN) with controlled diameters (100–200 nm) and large specific surface areas (∼112 m2/g) were prepared via a simple sol–gel method. Then, 10 wt% Ag nanocrystals (∼5 nm) were in situ generated in the MTN via solvothermal process, Ti3+ and oxygen vacancies also been introduced on their surface, thereby leading to a narrowed bandgap (∼2.9 eV) and strong absorption in the visible region. Finally, polydopamine (PDA) was decorated on the surface of Ag/bMTN to further improve their dispersity and photocatalytic activity. The degradation rate of tetracycline and the bactericide rate of E. coli could surpass 90 % and 99 %, which were mainly attributed to the generated O 2 − and the released Ag ions. [ABSTRACT FROM AUTHOR]

Abstract: Bi-doped hollow titania spheres were prepared using carbon spheres as template and Bi-doped titania nanoparticles as building blocks. The Bi-doped titania nanoparticles were synthesized at low temperature. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), UV–vis diffuse reflectance spectrum (DRS) and X-ray photoelectron spectroscopy (XPS). The effects of Bi content on the physical structure and photocatalytic activity of doped hollow titania sphere samples were investigated. Results showed that there was an optimal Bi-doped content (4%) for the photocatalytic degradation of methylene blue (MB). [Copyright &y& Elsevier]

Abstract: N-doped TiO2 nanotube arrays (NTN) were prepared by anodization and dip-calcination method. Hydrazine hydrate was used as nitrogen source. The surface morphology of samples was characterized by SEM. It showed that the mean size of inner diameter was 65nm and wall thickness was 15nm for NTN. The ordered TiO2 nanotube arrays on Ti substrate can sustain the impact of doping process and post-heat treatment. The atomic ratio of N/Ti was 8/25, which was calculated by EDX. Photoelectrochemical property of NTN was examined by anodic photocurrent response. Results indicated the photocurrent of NTN was nearly twice as that of non-doped TiO2 nanotube arrays (TN). Photocatalytic activity of NTN was investigated by degrading dye X-3B under visible light. As a result, 99% of X-3B was decomposed by NTN in 105min, while that of TN was 59%. [Copyright &y& Elsevier]

Abstract: N-doped titania hollow spheres (NTHS) were prepared by a one-pot hydrothermal method using urea as precursor of nitrogen. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectrum (DRS). The photocatalytic activity of as-prepared titania hollow spheres was determined by degradation of Reactive Brilliant Red dye X-3B (C.I. reactive red 2) under visible light irradiation, and was compared to non-doped titania hollow spheres and commercial P25 titania. Results indicated that the as-prepared NTHS showed highest photocatalytic activity. [Copyright &y& Elsevier]

Abstract: A novel photocatalyst (Ce, C-codoped titania) was synthesized through a modified sol–gel method under mild condition. The as-prepared sample was investigated by XRD, SEM, DRS and XPS. It was found that the as-prepared photocatalyst was composed of spheroidal particles, which were smaller than undoped ones. The absorbance spectrum of Ce, C-codoped TiO2 exhibited significant red-shift to visible region. It can be ascribed to appearance of a new electronic state in the middle of the TiO2 band-gap. Furthermore, cerium doping could slow the radiative recombination process of photogenerated electrons and holes in TiO2. Accordingly, for degradation of dye Reactive Brillint Red X-3B (C.I. reactive red 2) under visible light, the photocatalytic activity of Ce, C-codoped TiO2 improved much compared to other samples (C-doped TiO2, undoped TiO2 and P25). [Copyright &y& Elsevier]

Abstract: Nanocrystalline mesoporous titania was synthesized via a combined sol–gel process with surfactant-assisted templating method using cetyltrimethyl ammonium bromide (CTAB) as the structure-directing agent. The process was catalyzed by different acid (hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid). The prepared samples were characterized by XRD, TEM, BET and FT-IR. The photocatalytic activity of the samples was determined by degradation of phenol in aqueous solution. Results showed that different acid had different effect on the structure and crystal phase of the samples. The sample adjusted by phosphoric acid showed highest surface area and photocatalytic activity. The formation mechanism of the samples catalyzed by different acid was also discussed. [Copyright &y& Elsevier]

Abstract: Bi2O3–TiO2 composite films were synthesized by a sol–gel method under mild condition (i.e. low temperature and ambient pressure). The as-prepared films were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, infrared spectra and fluorescence spectra. The results showed that Bi2O3–TiO2 composite films were composed of anatase titania and Bi2O3. TiO2 particles were deposited on the surface of Bi2O3 to form uniform film. Incorporating Bi2O3 with TiO2 leads to increased surface OH group density. All Bi2O3–TiO2 composite films exhibited higher photocatalytic activity compared with pure TiO2 under solar irradiation, while the film with Bi/Ti atomic ratio of 1.25% showed the highest photocatalytic activity. Furthermore, the as-prepared films can be reused with little photocatalytic activity decreasing. Without any further treatment besides rinsing, the photocatalytic activity of Bi2O3–TiO2 (1.25%) films was still higher than 77% after six-cycle utilization. [Copyright &y& Elsevier]

[Display omitted] • Cr 2 O 3 as cocatalyst for CO 2 photoreduction was reported for the first time. • The crystal facets engineering and cocatalyst loading maximized the charge transfer. • The photocatalytic CO 2 conversion efficiency of TiO 2 increased by 30-fold. Implanting cocatalysts on semiconductor photocatalysts is considered as an essential strategy to promote reaction activity. However, the development of highly efficient cocatalysts remains challenging. In the present work, we construct independent Cr 2 O 3 as an efficient cocatalyst on the crystal facets engineered TiO 2 for photocatalytic CO 2 reduction for the first time. Moreover, a combined strategy of crystal facets engineering of TiO 2 and loading of Cr 2 O 3 cocatalyst is adopted to further promote the charge carriers' separation/transfer. In comparison with the cocatalyst-free TiO 2 without facets engineering, 2HF-TiO 2 /0.2Cr 2 O 3 exhibits near 30-fold enhancement on the CO 2 conversion efficiency. The enhanced photocatalytic activity is attributed to the maximal synergy of crystal facets engineering and cocatalyst loading for well-matched CO 2 reduction half-reaction and H 2 O oxidation half-reaction. These findings not only provide new insights for understanding the role of Cr 2 O 3 in photocatalytic systems but also may shed light on the design of photocatalysts from the perspective of overall photocatalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Charge interfacial transfer from Au/TiO 2 nanorod array to electrolyte was studied. • Au/TiO 2 perimeter sites were shown to be important for charge interfacial transfer. • Au-induced defects at Au/TiO 2 perimeter can promote electron interfacial transfer. Abstract In this research, by means of electrochemical cyclic voltammetries (CVs), the pathways of charge carrier interfacial transfer (IT) from TiO 2 and Au/TiO 2 rutile nanorod (NR) arrays to electrolyte were studied. For pure TiO 2 , the electron IT to O 2 takes place via both the conduction band (CB) states and the surface states (SS). The UV light illumination increases the electron IT via CB states, but inhibits that via SS pathway. The CV results also evidenced that the Au nanoparticles (NPs) on TiO 2 surface play dual roles of electron storage and electron IT pathway. Our results showed that the Au-induced defects, locating at Au/TiO 2 perimeter, form an important additional pathway for electron IT to O 2. UV light illumination increases the electron IT via Au NPs and Au-induced SS. In addition, we also revealed a special IT pathway of hot holes via the Au/TiO 2 perimeter contributes to the full water oxidation under visible light illumination. Therefore, the Au/TiO 2 perimeter region plays dual roles in the IT of both electrons and holes. Basing on these results, the IT pathways of charge carriers in Au/TiO 2 were illustrated from the viewpoint of energy band diagram. The photocatalytic degradation of methyl orange, photoelectrochemical oxidation of water, and photogeneration of free hydroxyl radicals (OH) were studied under UV and visible light illuminations. The association between the charge carrier IT pathways and the photocatalytic properties was also discussed. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) modified mesoporous single crystal TiO 2 microsphere (PANI/MS-TiO 2 ) with excellent photocatalytic activity was successfully prepared by a simple method of solution evaporation and chemisorption. The X-ray diffraction characterization demonstrated that the whole MS-TiO 2 kept the crystal type of anatase. The nitrogen adsorption-desorption characterization coupled with scanning electron microscopy indicated that the MS-TiO 2 possessed a unique mesoporous structure with high specific surface area, which resulted in the increased load of PANI on the surface of MS-TiO 2 and multiple light reflection in the photocatalyst. The UV–vis diffuse reflectance spectra confirmed that PANI/MS-TiO 2 presented more absorption ability in the visible light range than that of the pristine MS-TiO 2 . The transient photocurrent responses and electrochemical impedance spectroscopy (EIS) indicated the high photo responses and fast photogenerated charge separation efficiency of PANI/MS-TiO 2 . The photocatalytic activity of the PANI/MS-TiO 2 was evaluated by the photodegradation of RhB and MB under visible light irradiation. MS-TiO 2 photocatalyst with different molar ration of PANI had been prepared, and the results showed that the optimal photocatalyst (PANI/MS-TiO 2 (1:40)) exhibited the highest photocatalytic efficiency which is nearly three times as great as that of pristine MS-TiO 2 for the degradation of the RhB and MB under visible light irradiation. The remarkable performance of the PANI/MS-TiO 2 under visible light was attributed to its mesoporous single crystal structure with large surface, conductivity, as well as the synergistic effect between PANI and MS-TiO 2 . [ABSTRACT FROM AUTHOR]