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The preparation of reduced TiO2 photocatalysts with high Ti3+ concentration is a great challenge due to their instability in air. Here we report a new approach for the synthesis of reduced TiO2 with {001} facets exposed via a hydrothermal process. By the introduction of fluoride atoms, {001} and {101} facets are formed, which act as hole and electron collectors, respectively, for charge separation. By adjusting the volume of HF added, a rutile–anatase transition is observed for the first time. EPR spectra confirm the generation of Ti3+ species in the bulk of TiO2, and Ti3+ signals are studied in the anatase and rutile phases separately. The quantified EPR shows that reduced TiO2 samples present 14 000-fold more spins compared to the pristine TiO2, and the intensity can reach as high as 24.6 × 1019 spins per g. The obtained samples also have a unique disordered layer with a thickness of 1–2 nm on their surfaces, which contributes to the stabilization of the formed Ti3+ species by preventing their oxidation in air. In addition, the synthesized reduced TiO2 samples also exhibit wide-spectrum solar light absorption, especially in the near-infrared region. Owing to their enhanced solar light absorption, improved electron–hole separation and special facet exposure, these samples exhibit enhanced photocatalytic CO2 reduction performance and high CH4 selectivity under solar light irradiation, in the absence of a noble metal Pt as a co-catalyst. [ABSTRACT FROM AUTHOR]

Hollow structures with an efficient light harvesting and tunable interior component offer great advantages for constructing a Z-scheme system. Controlled design of hollow cobalt sulfide (Co9S8) cubes embedded with cadmium sulfide quantum dots (QDs) is described, using hollow Co(OH)2 as the template and a one-pot hydrothermal strategy. The hollow CdS/Co9S8 cubes utilize multiple reflections of light in the cubic structure to achieve enhanced photocatalytic activity. Importantly, the photoexcited charge carriers can be effectively separated by the construction of a redox-mediator-free Z-scheme system. The hydrogen evolution rate over hollow CdS/Co9S8 is 134 and 9.1 times higher than that of pure hollow Co9S8 and CdS QDs under simulated solar light irradiation, respectively. Moreover, this is the first report describing construction of a hollow Co9S8 based Z-scheme system for photocatalytic water splitting, which gives full play to the advantages of light-harvesting and charges separation. [ABSTRACT FROM AUTHOR]

CdxZn1−xSe/CoP composites have been well studied as effervescent photocatalysts for H2 evolution. These composites are highly efficient at 45.1 mmol h−1 g−1 and have a high quantum yield of 11.8% at ∼520 nm. The tunable energy band of CdxZn1−xSe facilitates photo-electrons transferring to CoP via chemical bonds between components. Advances in CdxZn1−xSe/CoP for photocatalytic H2 evolution provide a new strategy for future splitting of seawater. [ABSTRACT FROM AUTHOR]

Ti and carbon co-doped TiO photocatalysts were prepared hydrothermally to introduce the carbon, and followed by simple vacuum activation to achieve the Ti self-doping. The prepared co-doped photocatalysts were characterized by XRD, TEM, UV-Vis absorption spectra, EPR, and XPS. It was found that the co-doped TiO has dispersed nanoparticles and a narrower band-gap compared with the un-doped TiO and single-doped TiO. The experimental results displayed that the coke carbon generated on the surface of co-doped TiO acts as a photosensitizer and has the photosensitization effect under solar light irradiation. Except for the carbon sensitization effect, the Ti self-doping modification has a synergistic effect which is the reason for the effective photo-degradation of methyl orange under simulated solar light irradiation. [ABSTRACT FROM AUTHOR]

Vacuum-activated method was used to prepare Co and Ti co-modified TiO with the intention of enhancing visible light photo-catalytic performance, by expanding the visible light absorption and improving the quantum efficiency of the photo-catalytic reaction. The prepared co-modified catalysts were characterized by XRD, UV-DRS, XPS, EPR, etc. The characterization results indicate that the catalysts have a typical anatase crystalline form, and that some Co are incorporated on the surface of TiO, leading to the formation of Ti and oxygen vacancies. The impurity levels induced by Co and Ti doping are the reason for the enhanced visible light absorption, and the synergistic effect of cobalt, Ti and oxygen vacancies is responsible for the improvement of photo-catalytic activity. [ABSTRACT FROM AUTHOR]

Nanostructured titania and titanate have been considered as very important materials used in photocatalysis, photovoltaics, gas sensing and other electronic industries. In principle, their common structural feature is that the precursor phase involving TiO6 octahedra or similar building units may be converted to any of the nanostructured titania and titanate forms in a controllable way. Based on the atomic arrangement of ionic liquid-mediated NH4TiOF3 mesocrystals, TiO2 nanocrystals and titanate nanotubes were selectively obtained in H3BO3 and NaOH media, respectively, by using a simple hydrothermal method. Interestingly, the titanate nanotubes were successfully formed by extraction of NH4+ and F from NH4TiOF3 in a milder alkaline environment as low as 1 M NaOH, rather than conventional treatment of TiO2 in 10 M NaOH. The as-prepared TiO2 nanocrystals with exposed {001} facets exhibit a high photocatalytic activity and sedimentation rate as compared to commercial TiO2. Upon further doping or ion-exchange, the newly prepared TiO2 nanocrystals will show potential applications in the environment. [ABSTRACT FROM AUTHOR]

We report three-dimensional (3D) graphene-based hybrids of Fe2O3 nanocrystals grown in situ on graphene aerogels (Fe2O3/GAs) by a Stöber-like method. Compared with other reported Fe2O3/3D-graphene, Fe2O3/GAs have outstanding mechanical strength, high elasticity, ultralow mass, excellent electrical conductivity, good oil absorption capacity and a dispersion of nanoparticles. They have a 3D network structure with a high surface area of 316 m2 g−1 and physicochemical stability. 3D-GAs can inhibit the loss of Fe2+ and stabilize the conversion of Fe3+/Fe2+ in the photo-Fenton reaction. Compared with Fe2O3 and Fe2O3/2D-graphene (Fe2O3/GR), Fe2O3/GAs exhibit an ultrastable, solar-driven Fenton activity over a wide pH range of 3.5–9.0 for the first time. In addition, the highly-dispersed, nanosized Fe2O3 on the surface of the GAs makes the composite highly suitable for use in electrochemical capacitors. Although the Fe2O3/GAs only contain 18.3 wt% Fe2O3, they still yield a high and stable capacitance (151.2 F g−1) at a high discharge current density of 10 A g−1, which is better than that of Fe2O3/GR (93.6 F g−1). [ABSTRACT FROM AUTHOR]

This work reports a facile green solvothermal approach to synthesize rhombic anatase TiO 2 nanocrystals with small particle size of 50 nm and large percentage of {0 1 0} facets up to 73%. Tetrabutyl titanate (TBOT) is used as the titanium precursor while ethanol as the reaction solvent. The key strategy of this approach is to utilize ammonium acetate (AMAT) and ethylenediamine (EDA) in the non-aqueous system, where AMAT promotes the hydrolysis of TBOT and EDA serves as the capping agent. AMAT and EDA act synergistically to achieve a controlled growth of crystal structure of the anatase TiO 2 nanocrystals with exposed {0 1 0} facets. The mechanism for the nanocrystal growth was proposed based on experimental evidence. And the photocatalytic activities of the resultant nanocrystals were evaluated by degradation of methyl orange. This nanocrystal exhibits a superior photocatalytic activity in reference to commercial anatase TiO 2 and P25, owing to the large percentage of exposed {0 1 0} facets along with large surface area resulting from the small particle size. [ABSTRACT FROM AUTHOR]

The nanocomposites of reduced graphene oxide based nitrogen doped TiO 2 (N–TiO 2 –RGO) and reduced graphene oxide based nitrogen and vanadium co-doped TiO 2 (N, V–TiO 2 –RGO) were prepared via a facile hydrothermal reaction of graphene oxide and TiO 2 in a water solvent. In this hydrothermal treatment, the reduction of graphene oxide and the intimate contact between nitrogen doped TiO 2 (N–TiO 2 ) or nitrogen and vanadium co-doped TiO 2 (N,V–TiO 2 ) and the RGO sheet is achieved simultaneously. Both N–TiO 2 –RGO and N,V–TiO 2 –RGO nanocomposites exhibit much higher visible light photocatalytic activity than N–TiO 2 and N,V–TiO 2 , and the order of visible light photocatalytic activity is N,V–TiO 2 –RGO > N–TiO 2 –RGO > N,V–TiO 2 > N–TiO 2 > TiO 2 . According to the characterization, the enhanced photocatalytic activity of the nanocomposites is attributed to reasons, such as enhancement of adsorption of pollutants, light absorption intensity, minimizing the recombination of photoinduced electrons and holes and more excited states of these nanocomposites under visible light irradiation. Overall, this work provides a more marked contrast of graphene based semiconductor nanocomposites and a more comprehensive explanation of the mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Fe TiO2 photocatalysts were prepared by a sol–gel process and low-temperature solvothermal method. The obtained samples were characterized by XRD, UV–vis DRS, FT-IR, BET, EPR and XPS. Compared with undoped TiO2 and S doped TiO2 photocatalysts, the Fe TiO2 photocatalysts exhibited much higher photocatalytic activity for phenol degradation under visible light irradiation. The optimal ratio of Fe/Ti is 1.0at%. It was revealed that the band gap of Fe TiO2 was obviously decreased, extending the light response of TiO2 into visible light region, and sulfate ions were absorbed on the surface of the TiO2. The high visible light photocatalytic activity of TiO2 was assigned to the beneficial co-effects between S and Fe. The doped Fe(III) and SO4 2− anchored on TiO2 surface are favorable for the separation of photo-induced electrons and holes, suppressing the recombination of electrons and holes and consequently promoting the formation of hydroxyl radical. [Copyright &y& Elsevier]

Abstract: A series of TiO2 catalysts self-doped with Ti3+ were successfully synthesized by a simple one-step solvothermal method with low-cost NaBH4 added as a reductant. During NaBH4 reduction, large amounts of NaBO2 and carbonaceous impurities covered the surface of the TiO2 self-doped with Ti3+, resulting in an inhibition of visible-light absorption and photocatalytic activity. In the preparation, HCl solution was used to wash off the by-product NaBO2 and carbonaceous impurities coated on the surface of the catalysts. The samples were characterized by XRD, UV-DRS, ESR, XPS, and FT-IR analyses. After HCl washing, the photocatalytic activity of the Ti3+-doped TiO2 increased markedly, while the Ti3+ content remained the same. Furthermore, it was found that the visible-light photocatalytic activity of Ti3+-doped TiO2 depended on the amount of Ti3+ added, while there was no significant impact of Ti3+ doping on its UV-light photocatalytic activity. [Copyright &y& Elsevier]

Metal–organic frameworks (MOFs) are potential photocatalytic materials for CO2 reduction, however, still limited by their low efficiency. In this work, cobalt decorated UiO-66-NH2 (xCoNU, x presents the mass friction of cobalt) were successfully synthesized through an economic NaBH4 treating method and applied for CO2 photocatalytic reduction. It was confirmed that cobalt worked as the active site in the system, and an optimized CO yielding rate of 1.93 mmol g−1 h−1 in 3 h was achieved on 5CoNU, which is 10.2 times higher than that of UiO-66-NH2. Characterization results revealed that the highly dispersed cobalt in xCoNU accelerates the charge separation and electron transport in the photocatalytic system, improving the photocatalytic CO2 reduction performance. This work provides a simple and convenient method to modify MOFs with metal cocatalyst, and is expected to advance the development of efficient CO2 photoreduction catalysts. [ABSTRACT FROM AUTHOR]

Abstract: NH4F was used instead of conventional organic silylation agent as the hydrophobic modifier to synthesize the super-hydrophobic mesocellular foams (MCF) loaded with nano-sized TiO2 photocatalysts in its pore channels, which could be considered as an extractant for organics. Compared to organosilane modified catalysts, NH4F-modified MCF/TiO2 has a more stable super-hydrophobic property and much higher photocatalytic activity. It was found that only using isopropanol as the solvent, the NH4F-modified catalyst showed super-hydrophobic property. It is believed that the solvent plays a role in controlling the exchange between surface OH groups and F ions. The special structure of supported mesoporous catalyst greatly facilitated the surface fluorination, which together with the Ti3+ generation led to its excellent adsorption capacity and UV/visible light photocatalytic activity. This novel super-hydrophobic mesoporous photocatalyst has a large application potential in the field of photocatalysis, shipbuilding, and other industries. [Copyright &y& Elsevier]

Abstract: Well-ordered mesoporous TiO2 co-doped with nitrogen and ytterbium was successfully synthesized by an evaporation-induced self-assembly process. The as-prepared and calcined mesoporous TiO2 materials were characterized by X-ray diffraction, transmission electron microscope, UV–vis absorbance spectroscopy, X-ray photoelectron spectroscopy, fourier transform infrared and N2 adsorption–desorption measurements. After calcinations at 350°C, the TiO2 co-doped with nitrogen and 3% ytterbium had the highest surface area (219m2 g−1) and retained ordered structures. Under visible light irradiation, 75% of 20mg/L phenol solution was degraded after 10h and 10mg/L rhodamine B (RhB) was decomposed completely after 4h. The significant enhancement in the photocatalytic activity of the modified TiO2 is attributed to the synergistic effect of N and Yb. The N dopant extended the absorption to visible region and the Yb dopant was beneficial in stabilizing the mesoporous structure and restraining the recombination of photogenerated holes and electrons. [Copyright &y& Elsevier]

Abstract: Carbon and boron co-doped TiO2 photocatalysts were prepared firstly by the gel-hydrothermal method, that is, synthesized through sol–gel process followed by hydrothermal in the glucose solution. The prepared photocatalysts were characterized by XRD, Raman spectra, TEM, N2 physical adsorption, XPS, and UV–vis absorption spectra. It was found that the co-doped TiO2 has a larger BET surface areas and a narrower band gap than undoped TiO2. The experimental results show that the coke carbon generated on the carbon doped TiO2 surface act as a photosensitizer and has the photosensitization effect under the visible light. Except for carbon sensitization effect, the boron and carbon co-doped TiO2 has synergistic effect which is responsible for effective photo-degradation of 2,4-dichlorophenol in the visible light irradiation. [Copyright &y& Elsevier]

Abstract: N and F-codoped TiO2 microspheres were prepared by ethanol solvothermal method, using tetrabutyl titanate as precursor, urea as a nitrogen source and ammonium fluoride as a fluorine source. The prepared catalysts were characterized by X-ray diffraction (XRD), N2 physical adsorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible adsorption spectroscopy and photoluminescence spectra (PL). The photocatalytic performance of N–F–TiO2 microspheres was evaluated by analyzing the degradation of acid orange 7 (AO7) under visible light irradiation. It was found that N–F–TiO2 microsphere with mesoporous structure is composed by anatase phase, and the interstitial doping of nitrogen into TiO2 lattice might be responsible for the visible light response. Meanwhile, F-doping could not only retard the transformation from anatase to rutile, but also increase the concentration of OH in solution, which is beneficial for improving the photodegradation rate of organic compounds. The synergetic effect of nitrogen and fluorine doping leads to the high activity of N–F–TiO2 for the photodegradation of AO7 under visible light irradiation. [ABSTRACT FROM AUTHOR]