Herein we describe the mechanism of crystallization of Al3+ with amorphous TiO2 on a TiO2 film, and found that the resultant Al2TiO5 was able to improve the average efficiency of planar perovskite solar cells (PSCs) from 15.4 to 17.2%. The electron lifetime in these Al-PSCs was about 3 times longer than that in unmodified PSCs. The O 1s X-ray photoelectron spectrum of the TiO2/CH3NH3PbI3 interface indicated that the oxygen vacancy or defect peak decreased by more than 31% on modifying the interface with Al2TiO5. The stability of the PSCs was improved substantially: Al-PSCs had still 88% of their initial value after 1440 hours, while the efficiency of the reference PSCs decreased to 68% of their initial value.

Two types of secondary emitter materials, the rare earth oxides (RE2O3) doped Mo cermet cathodes and the Y2O3-W matrix pressed cathode, are introduced in this paper. According to the calculation results, Y2O3 exhibits the best secondary emission property among Y2O3, La2O3, CeO2 and Lu2O3. The rare earth oxides co-doped Mo cathodes in which Y2O3 is the main active substance exhibit better secondary emission property than single RE2O3 doped Mo cathode. The results obtained by the Monte-Carlo calculation method show that the secondary electron emission property is strongly related to the grain size of the cathode. The decreasing of the grain size reduces the positive charge effect of the rare earth oxide due to the electrons supplement from the metal to the rare earth oxide, whereby the secondary electrons are easier to escape into the vacuum. Y2O3 is introduced into Ba-W cathode to fabricate a pressed Y2O3-W matrix dispenser cathode. The result indicates that the secondary emission yield of the Ba-W cathode increases from 2.13 to 3.51 by adding Y2O3, and the thermionic emission current density (J0) could reach 4.18 A/cm2 at 1050 °Cb.

•MgO films with controlled thicknesses on Ag-3Mg alloys were prepared by activation in low vacuum with oxygen.•Superior secondary electron yield was obtained for the Ag-3Mg alloy with proper thickness of MgO film.•Oxygen pressure during the activation process is crucial for obtaining good secondary electron yield for Ag-3Mg alloys.•The mechanism of secondary electron emission in MgO films is discussed.MgO thin films of different thicknesses were prepared on polished Ag-3wt%Mg alloy by an activation process at 500–650 °C under oxygen pressures of 0.5–10.0 Pa. The influence of the thickness of MgO film on the secondary electron yield of the Ag-3wt%Mg alloy is investigated. The alloy with an MgO film of moderate thickness of 65 ± 1 nm shows the highest secondary electron yield of 10. Oxygen pressure below 10.0 Pa is crucial for the formation of intact MgO film on the top surface. Computational simulation analysis reveals that the maximum yield occurs when the penetration depth of primary electrons is 13–18 nm less than the thickness of MgO film. Electron supply of this extra MgO film is allowed by an electron tunneling mechanism under certain bias voltage. The replenishment of new electrons to the electron deficient surface is crucial for obtaining optimized secondary electron yields for Ag-Mg alloy cathodes.Download high-res image (240KB)Download full-size image

•The OATMS/GP composite was well synthesized by hydrothermal-driven assembly method.•Mesoporous TiO2, mixed-phase and graphene were integrated into a composite system.•The OATMS/GP composite showed excellent photocatalytic degradation of gaseous NO.•The active species O2− and OH were detected and OH played the important role.We design and synthesize a novel graphene embedded orient-assembled TiO2 mesoporous spheres composite (OATMS/GP) evidenced by SEM, TEM and optical spectra. Mesoporous structure, characteristics of single-crystal-like TiO2, mixed phases of anatase and rutile and embedding of graphene have been integrated into a composite system to investigate the structure-property relationship for enhancing photocatalytic activity. Three-dimensional (3D) open mesoporous TiO2 microspheres were well-constructed by the radially oriented self-assembly of single-crystal-like TiO2 nanowires. The aggregation of nanowires leads to the formation of 3D hierarchical microsphere including mesopores that is convenient for light harvesting and adsorption of reaction molecules. Especially, the phase ratio of anatase and rutile in the composite is readily tunable by the change of reaction agents. The incorporation of graphene accelerates the electron transfer and further prolongs the lifetime of the photoinduced electron–hole pairs. This unique structure makes the composite ideal be an efficient photocatalyst for the removal of pollutants. The OATMS/GP composite for degradation of Nitric Oxide (NO) shows an excellently photocatalytic activity and stability during photocatalytic reaction. The results presented here are expected to make a contribution to preparing delicately photocatalytic nanocomposites toward the promising applications for air purification and solar energy utilization.

This paper reports first on the novel synthesis of hierarchical tin dioxide (SnO2) porous microspheres in the absence of a template using a simple spray reaction technique and annealing at 500–800 °C. The SnO2 microspheres obtained are tetragonal phase and approximately 2.2–2.7 μm in diameter, and they consist of 6.7–23.1 nm crystallites and possess hierarchical pores and Brunauer–Emmett–Teller (BET) surface areas of up to 55 m2 g−1. Using ultraviolet-visible absorption spectra analysis, it is found that SnO2 crystallites demonstrate a quantum size effect, resulting in a widening of the band gap of the SnO2 spheres. This band gap can be tuned from 3.99 eV (800 °C) to 4.26 eV (600 °C) by varying the annealing temperature. Using separated SnO2 porous spheres as the scattering layer of the photoanode for dye sensitized solar cells (DSSCs), the solar light-electricity conversion efficiency (maximum: 6.0%) is increased by up to 31.9% and 28.2% compared to cells using a commercial SnO2 powder and P25 nanopowder as the scattering layers, respectively, under the same conditions.

Highly efficient photo-generated carrier transfer is one of the key factors in determining the performance of organic–inorganic hybrid perovskite solar cells (PSCs). Here, we demonstrate a strategy for improved hole transfer and collection by employing a composite hole transporting material (HTM) consisting of free standing Ni nanobelts dispersed in the widely used 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). It is found that power conversion efficiency (PCE) and ambient stability of mesoscopic PSCs have been improved. To be more specific, in order to prevent significant charge recombination induced by direct contact of the metal Ni with a perovskite absorber, a spiro-OMeTAD intermediate layer was spin-coated on the CH3NH3PbI3 layer prior to the sequentially deposited layers of Ni nanobelts and spiro-OMeTAD. With this architecture, the optimized PSC achieved a champion PCE of 16.18% with a short-circuit current density (Jsc) of 21.64 mA cm−2, an open-circuit voltage (Voc) of 1.02 V, and a fill factor (FF) of 73.3% under reverse scanning. Despite the small J–V hysteresis, a higher stabilized efficiency up to 14.47% near the maximum power point could be reached for the device fabricated with 1.8 mg mL−1 Ni nanobelts compared with the pristine one (12.05%). However in the presence of highly hygroscopic lithium-bis(trifluoromethane) sulfonimide (Li-TFSI), PSCs in conjunction with Ni nanobelts present an impressively favorable ambient stability with an observed PCE retention rate of over 85% after 4-week storage with exposure to ambient air without any encapsulation.

•A facile route is developed to convert flue gas desulfurization gypsum waste.•Morphologies and crystal phases of the gypsum products can be controlled.•The addition amount of sodium dodecyl sulfate influences the crystallization.In this work, we studied the phase- and morphology-controlled crystallization of gypsum by using flue-gas-desulfurization (FGD) gypsum source materials in HCl–H2O solution system at atmospheric pressure. The influence of the crystallization regulator sodium dodecyl sulfate (SDS) on the conversion process was examined. The results indicate that oxide impurities in FGD gypsum are removed by the treatment in this designed solution-phase system. Without the addition of SDS surfactant, calcium sulfate hemihydrate with fiber morphology is obtained and as the addition amount of SDS increases from 0.6 wt% to 5.4 wt%, the prepared sample transforms from column-like calcium sulfate hemihydrate to layer-structured calcium sulfate anhydrite. It is proposed that SDS selectively adsorbs on top (204) facet at a low SDS concentration (0.6 wt%), resulting in the decrease of aspect ratio compared with fiber-like calcium sulfate hemihydrate (without SDS addition). Layered SDS micelles are formed when 5.4 wt% SDS is added, and the soft template function, as well as the hydrophobic interaction of alkyl group in the surfactant, generates the layer-structured calcium sulfate anhydrite. The study provides a facile method for treating solid waste FGD gypsum.A facile acid solution method was developed to convert solid waste flue-gas-desulfurization gypsum into pure gypsum products with controlled crystal phase and morphology.

A new hydrothermal system has been designed to recycle waste WC–Co hardmetal with low cobalt (Co) content (3 %). In the solution system, nitric acid was designed to dissolve Co, H2O2 served as oxidant to accelerate the oxidation of the WC–Co hardmetals, and fluorine (F−) was designed to dissolve and recrystallize generated tungsten oxides, which were found to possess a layered structure using scanning electron microscopy and transmission electron microscopy. The obtained tungsten oxides were identified as WO3·0.33H2O by X-ray diffraction and their specific surface area was measured as 89.2 m2 g−1 via N2 adsorption–desorption techniques. The present layered structure tungsten oxides exhibited a promising capability for removing lead ion (Pb2+) and organic species, such as methyl blue. The adsorption model was found to be in agreement with Langmuir isotherm model. Given the facile synthesis procedure and promising properties of final products, this new approach should have great potential for refining some other waste hardmetals or tungsten products.

TiO2–Y2O3 core–shell nanoparticles for dye-sensitized solar cells (DSSCs) have been fabricated by a solvothermal technique. The heterostructure of TiO2 nanoparticles coated with porous Y2O3 is confirmed with transmission electron microscopy. The bonding of the Y2O3 coating on the TiO2 surface is quantitatively analyzed in terms of the Lifshitz–van der Waals and electrostatic contributions to the surface free energy of the particles. TiO2 and Y2O3 constitute a core–shell heterojunction because the Fermi levels merge; this increases the open-circuit voltage. Higher recombination resistances are obtained in DSSCs with porous Y2O3-coated TiO2 compared with those in the reference cells, indicating “backscattering” inhibition of the porous Y2O3 barrier on TiO2 nanoparticles. Moreover, smaller transport resistances and longer electron lifetimes are achieved in DSSCs with TiO2–Y2O3 core–shell nanoparticles. Compared with a reference cell, the VOC of a DSSC with a partial Y2O3 coating on the surface of the TiO2 nanoparticles improves from 683 to 738 mV and the Jsc from 14.15 to 15.35 mA·cm–2, whereas the conversion efficiency increases by 15.2%.Keywords: Backscattering barrier; Heterojunction; Photovoltage; Photovoltaic performance; Porous coating; Yttria;

TiO2 mesoporous nanoparticles (NPs) doped with yttrium (Y) ions are fabricated via an environmentally friendly and facile solvothermal method to serve as a photoanode for dye sensitized solar cells (DSSCs). X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and N2 adsorption–desorption tests are used to characterize the influence of yttrium dopant on the properties of TiO2 NPs. The prepared Y-doped TiO2 NPs show the anatase phase and exhibit Ti–O–Y bonds. The photovoltaic performance is primarily associated with the morphological parameters of the NPs. At the optimum Y concentration of 3 at%, the short circuit current density increased from 13.20 to 15.74 mA cm−2, full sun solar power conversion efficiencies increased from 6.09% up to 7.61% as compared to the blank DSSC.

•A new cathode, LaCx doped W cathode, is prepared by a powder metallurgy method.•The cathode with 10 wt% LaCx exhibits a current density of 3.12 A/cm2 at 1400 °Cb.•The j0 of this cathode meets the requirement for magnetron application.•High temperature carburization and activation processes are eliminated.A new type of thermionic cathode, lanthanum carbide doped tungsten cathode, has been fabricated through a spark plasma sintering method by using the mixed powders of lanthanum carbide and tungsten. Lanthanum carbide powder was prepared by a levitation melting method in vacuum. The thermionic emission properties have been investigated. It is found that the concentration of lanthanum carbide has a significant influence on the emission properties of the cathodes. The emission current density of the tungsten cathode at 1400 °Cb was increased dramatically from 1.09 to 3.12 A/cm2 with the increase of concentration of lanthanum carbide from 3.5 to 10 wt%. The emission mechanism of the cathode has been discussed.

Hierarchical WO3 hydrates have been synthesized via an ion exchange method using Na2WO4·2H2O as a precursor. The morphologies and phase structures of WO3 hydrates can be controlled by tuning the concentration of Na2WO4·2H2O solution. The as-synthesized urchin-like WO3·0.33H2O and flower-like WO3·H2O possess high specific surface area and numerous adsorption functional groups, such as WO and O–H bonds, on the surface. These characteristics result in excellent adsorption performance for both organic dyes and heavy metal ions from wastewater. The maximum uptake capacities of the urchin-like WO3·0.33H2O for methylene blue and Pb2+ are 247.3 and 248.9 mg g−1, respectively and those of the flower-like WO3·H2O are 117.8 and 315.0 mg g−1, respectively. The formation mechanism of such hierarchical mesoporous urchin-like WO3·0.33H2O and adsorption mechanism are studied in this paper.

Ordered mesostructured TiO2 thin films were constructed through a method that combined sol–gel with evaporation-induced self-assembly (EISA). It was found that the calcination temperature, as well as the type of block copolymer, could vary the TiO2 mesoporous structure. Based on tension stress calculated by the surface energy of crystallites and the compression calculated by interface energy between the crystallites, the thermodynamic study for the sample had been carried out and the critical crystallite size expression of the mesoporous film was presented for the prediction of the thermal stability of the mesoporous structure at high temperature. It was also found that varying the mass ratio of templating agent to inorganic precursor could adjust the pore size of mesoporous TiO2. The pore size regulating mechanism had been discussed. The sample calcined at 450–500 °C, which had a higher specific surface area and larger pore size, exhibited higher photocatalyzed destruction capability of Methylene Blue.Keywords: film; mesoporous structure; photocatalyzed destruction; TiO2;

A new solid niobic acid phase, H2(H2O)Nb2O6, with fluorine (F) doping was crystallized using hydrothermal chemistry. F-doped H2(H2O)Nb2O6 octahedra could function as an efficient heterogeneous catalyst for the photodegradation of organic pollutants in water under UV light irradiation. The high photocatalytic activity of the F-doped H2(H2O)Nb2O6 materials is attributed to a synergistic effect of the specific surface area, the surface characteristics and the crystal structure. Our results suggest novel ways of controlling the crystallization of niobium oxides, further the fundamental understanding of their structure–property relationships, and may lead to their application in fields such as environmental protection and energy production.

To improve the contact between platinum catalyst and titanium substrate, a layer of TiO2 nanotube arrays has been synthesized before depositing Pt nanoflowers by pulse electrodeposition. Dramatic improvements in electrocatalytic activity (3×) and stability (60×) for methanol oxidation were found, suggesting promising applications in direct methanol fuel cells. The 3× and 60× improvements persist for Pt/Pd catalysts used to overcome the CO poisoning problem.

We report the design and synthesis of two hematite (α-Fe2O3)-based nanomaterials based on effective hydrothermal conversion of chemically metastable K1.33Mn8O16 nanowires (KWs) in Fe(NO3)3 aqueous solution. Insights are gained into the functions of sodium dodecyl benzene sulfonate (SDBS) and the mechanisms for generating large quantities of α-Fe2O3 hollow structures (FHSs) and K1.33Mn8O16@α-Fe2O3 heterostructured nanowires (KFHWs) in solution phase. The controllable growth dynamics allows convenient control over the morphology and production of the hematite-based nanostructures. Adsorption experiments indicate that the resulting hematite-based materials are powerful nanosorbents for swift removal of Congo red from wastewater at room temperature. The adsorption kinetics and adsorption isotherm are also investigated and the findings indicate that the as-prepared KFHW and FHS hold great potential as environmentally friendly filter materials for water purification and organic waste removal.

Enhancing surface area is one of the efficient ways to improve photochromic sensitivity of WO3·0.33H2O. Hierarchical WO3·0.33H2O mesoporous nanorod assemblies were synthesized via proton exchange by adjusting the concentration of Na2WO4·2H2O. When the concentration of Na2WO4·2H2O is 2.0 g L−1, mesoporous nanorods with 10∼20 nm in diameter and an average pores size of about 4 nm were obtained. The novel WO3·0.33H2O porous structure possesses highly photochromic sensitivity and fatigue resistance properties. It exhibits visible-light-driven photochromic response due to large specific surface area originated from the mesoporous structure. The formation of mesopores is due to the volume decreasing in the transformation process from WO3·H2O to WO3·0.33H2O.Graphical abstractHierarchical WO3·0.33H2O mesoporous nanorod assemblies are synthesized through proton exchange route and exhibit highly photochromic sensitivity.Highlights► WO3·0.33H2O mesoporous nanorod assemblies was synthesized via proton exchange. ► It possesses highly photochromic sensitivity and fatigue resistance properties. ► The formation of mesopores is due to the volume decreasing.

•A transparent ordered 12.5 μm-thick TiO2 nanotube film has been obtained.•The structure zone model of Ti film has been presented.•TiO2 nanotube film has a high transmittance in the visible light range•The impedance of fluorine-doped tin oxide is responsive to light.Highly ordered TiO2 nanotube array films were fabricated on conducting fluorine-doped tin oxide (FTO) glass substrate in NH4HF2/glycol electrolyte via anodization of Ti film, which was deposited by direct current magnetron sputtering. Ti films obtained by direct current magnetron sputtering method have three growth regions and that deposited at 410 °C has smooth surface which is favorable for the anodization. The anodization voltage affects the diameter of TiO2 nanotube and the reason has been discussed. A 12.5 μm-thick TiO2 nanotube array film has been obtained and exhibits a high transmittance of 32% in the visible light range. The bandgap of the thin film is calculated to be 3.08 eV based on the UV–vis transmission spectra, and its tail extends to 2.94 eV. The electrochemical impedance spectroscopy indicates that the impedance TiO2 nanotube film decreases after light illumination.

With its excellent anticorrosion and biocompatibility, tantalum, as a promising endosseous implant or implant coating, is attracting more and more attention. For improving physicochemical property and biocompatibility, the research of tantalum surface modification has increased. Tantalum oxide (Ta2O5) nanotube films can be produced on tantalum by controlling the conditions of anodization and annealing. The objective of our present study was to investigate the influence of Ta2O5 nanotube films on pure tantalum properties related with anticorrosion, protein adsorption, and biological function of rabbit bone mesenchymal stem cells (rBMSCs). The polarization curve was measured, the adsorption of bovine serum albumin and fibronectin to Ta2O5 nanotubes was detected, and the morphology and actin cytoskeletons of the rBMSCs were observed via fluorescence microscopy, and the adhesion and proliferation of the rBMSCs, as well as the osteogenic differentiation potential on tantalum specimens, were examined quantificationally by MTT and real-time PCR technology. The results showed that Ta2O5 nanotube films have high anticorrosion capability and can increase the protein adsorption to tantalum and promote the adhesion, proliferation, and differentiation of rBMSCs, as well as the mRNA expression of osteogenic gene such as Osterix, ALP, Collagen-I, and Osteocalcin on tantalum. This study suggests that Ta2O5 nanotube films can improve the anticorrosion, biocompatibility, and osteoinduction of pure tantalum, which provides the theoretical elaboration for development of tantalum endosseous implant or implant coating to a certain extent.Keywords: anticorrosion; biocompatibility; bone mesenchymal stem cell; osteogenesis-related genes; protein adsorption; Ta2O5 nanotube array;

Complex silver (Ag) crystals were crystallized by a technically flexible top-down chemical etching method in a solution phase. Microscale shaped Ag particles were first grown via a galvanic displacement of Ag on commercial Nb metal foil. The metastable Ag precursor was chemically active in solution containing NO3− and HF, readily crystallizing complex Ag microstructured crystals by a HNO3-assisted etching. Insights are gained into the functions of HF and the mechanisms of generating large quantities of anisotropically shaped particles in the solution-phase. The crucial influences of HF concentration and reaction time on the morphology of Ag microstructures have also been established. This current top-down chemical route provides an extremely simple, mild, and effective recipe to crystallize Ag, which is also possible to expand to grow more metal crystals with controlled structures and particle morphologies.

Using the triblock copolymer Pluronic F127 (EO106PO70EO106) as the templating agent and Ti(OBun)4 as the titanium source, mesostructured TiO2 thin films were constructed through the sol–gel and evaporation-induced self-assembly method. The effect of the calcination temperature on the mesostructure and on the hydrophilicity of the obtained mesoporous TiO2 thin films was investigated. Small-angle and wide-angle X-ray diffractions, transmission electron microscopy, N2 adsorption–desorption, and contact angle measurements were used to characterize the as-synthesized TiO2 thin films. It was shown that the synthesized mesoporous TiO2 materials exhibited an excellent thermal stability and possessed pores with a diameter larger than 7 nm and a narrow pore-size distribution, and thick inorganic walls composed of nanocrystalline anatase. The calcination temperature affected the stability of the mesoporous structures. In the range of 450–600 °C, the mesoporous framework was stable and the pore size was from 7.3 to 7.8 nm. Above 600 °C, however, the structure collapsed partially. On the basis of the film structure, a four-coordinate channel mode was proposed and the collapse criterion for the mesoporous structure was established through thermodynamic calculation. The synthesized mesoporous TiO2 thin films showed excellent hydrophilicity without light illumination; for example, the film obtained after being treated at 600 °C had a contact angle of about 22.5°, whereas the sample treated at 500 °C (the particle and pore sizes were 10.2 and 7.5 nm, respectively) showed the optimal photoinduced hydrophilicity, with the contact angle of about 9.5°.

The multi-layer TiO2 nanotube array thin films have been formed by anodic oxidation method via adjusting the outer voltage during oxidation process in glycerol electrolyte containing 0.3% NH4HF2. The diameter of the nanotube array increases with the outer voltage, and the length of nanotube in every layer increases with the anodic oxidation time. These multi-layers bring new possibilities to tailor the properties of the TiO2 nanotube array thin films formed via anodic oxidation method. Further, such multi-layer structure provide a new approach to evaluate the growth rate of TiO2 nanotube, which will help us to understand more deeply the formation mechanism of the TiO2 nanotubes. The growth rate of TiO2 nanotube array is respectively 1.2 and 3.6 μm/h under the anodic voltage of 30 V and 60 V. These multi-layer TiO2 nanotube array thin films may exhibit lots of potential applications in photoelectrochemical fields.

Fibrous TiO2 and plate-like TiO2 were obtained through the hydrothermal synthesis method by using two kinds of protonic tetratitanate (H2Ti4O9), prepared by ion exchange of K2Ti4O9 and HCl, or milled K2Ti4O9 and HCl, respectively. The product made by hydrothermal treatment of H2Ti4O9 without milling in water consisted of anatase TiO2 and retained the fibrous morphology of the precursor but with fine crystals attached on the surface, formed by the in situ topotactic transformation reaction and dissolution and recrystallization. On the other hand, TiO2 prepared with H2Ti4O9 obtained through ion exchange of milled K2Ti4O9 and HCl had plate-like shape, namely retaining the morphology of nanosheets of H2Ti4O9 through an in situ transformation process. Under ultraviolet irradiation, 70% methyl orange degradation by TiO2 nanosheets was about 3.3 times higher than that by fibrous TiO2. The higher surface area, higher pore volume, and smaller particle size led to the higher photocatalytic activity of the TiO2 nanosheets.

Mesoporous TiO2−xAy (A = N, S) thin films were fabricated using thiourea as a doping resource by a combination of sol-gel and evaporation-induced self-assembly (EISA) processes. The results showed that thiourea could serve two functions of co-doping nitrogen and sulfur and changing the mesoporous structure of TiO2 thin films. The resultant mesoporous TiO2−xAy (A = N, S) exhibited anatase framework with a high porosity and a narrow pore distribution. The formation of the O–Ti–N and O–Ti–S bonds in the mesoporous TiO2−xAy (A = N, S) were substantiated by the XPS spectra. A new bandgap in visible light region (520 nm) corresponding to 2.38 eV could be formed by the co-doping. After being illuminated for 3 h, methyl orange could be degraded nearly completely by the co-doped sample under both ultraviolet irradiation and visible light illumination. While pure mesoporous TiO2 could only degrade 60% methyl orange under UV illumination and showed negligible photodegradation capability in the visible light range. Furthermore, the photo-induced hydrophilic activity of TiO2 film was improved by the co-doping. The mesoporous microstructure and high visible light absorption could be attributed to their good photocatalytic acitivity and hydrophilicity.

Based on anodic aluminum oxide (AAO) templates prepared in different acidic solutions, highly ordered aligned titania nanotubes array films have been successfully prepared by the liquid phase deposition method. The effect of AAO template type on the microstructure of titania film have been studied. Using the template with a certain volume fraction of Al2O3 (less than 0.71), ordered aligned titania nanotubes were obtained, characterized with an outer diameter of 200 nm and an inner diameter of 100 nm, respectively. However, titania existed as ordered aligned nanorods with the diameter of 100 nm when the template with large volume fraction of Al2O3 (larger than 0.71) was used. TiO2 thin films calcined at 400°C for 4 h have an anatase phase and exhibit good photocatalytic activity, i.e., 75% methylene blue could be degraded under ultraviolet irradiation for 2 h.

Nitrogen and sulfur co-doped mesoporous TiO2 thin films were fabricated using thiourea as a doping resource by the combination of the sol–gel and evaporation-induced self-assembly (EISA) processes. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, and UV–vis spectra were performed to characterize the as-synthesized mesoporous TiO2 materials. The XPS result shows that O–Ti–N and O–Ti–S bonds in the (S, N)-codoped mesoporous TiO2 were formed. The resultant mesoporous (S, N)-codoped TiO2 exhibited anatase framework with a high porosity and a narrow pore distribution. After being illuminated for 3 h, methyl orange (MO) could be degraded completely by the co-doped sample under the ultraviolet irradiation, whereas mesoporous TiO2 film without doping could only degrade 60% MO. After being illuminated by visible light, the water contact angles of the mesoporous co-doped TiO2 samples decreased slightly, but the pure TiO2 mesoporous film exhibited no change in the hydrophilicity.

Mesoporous TiO2 thin films were prepared by using tetrabutyl titanate as the inorganic precursor and triblock copolymer (Pluronic F127) as the structure directing agent. The obtained mesostructured TiO2 thin film exhibits a high thermal stability, which can sustain 600 °C thermal treatment. The small angle XRD and wide angle XRD patterns indicate that the samples have mesoporous channel and are composed of anatase. The corresponding TEM images show that the homogeneous mesostructure and very thick pore walls (about 9–13 nm) are formed in the obtained thin films, which could be responsible for the high thermal stability of the framework. In addition, the samples have narrow pore diameter distribution and a mean pore size of 7.4 nm.

Nanocomposite titania/tetratitanate particles were prepared by utilizing the electrostatic interaction of the colloidal tetratitanate nanosheets and TiO2 powders through dispersing TiO2 into tetratitanate solution at pH4. The samples were characterized by X-ray powder diffraction, transmission electron microscopy, chemical analysis, and photocatalytic activity measurement. The crystallites of Ti4O92− in the form of tetratitanate nanosheets have lateral size around 100 nm. The visible light responsive photocatalytic activity of rutile nanoparticles could be improved by forming nanocomposite with layered tetratitanate. The high specific surface area of this kind of composite and a certain amount of mesopores in nanocomposite powder could be responsible for better performance in the NO elimination.

La2O3–Mo, Y2O3–Mo, Gd2O3–Mo and Ce2O3–Mo were prepared by liquid–liquid doping combined with spark plasma sintering. The microstructure and surface behaviour of rare earth oxide of the cathode have been studied by microscope, Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS) methods. Among these four kinds of cathode, Y2O3–Mo cathode exhibits the best secondary emission property, i.e., the maximum secondary emission yield could reach 5.24. The penetration depth of primary electrons and escape depth of secondary electrons have been calculated and the energy distribution of primary electrons in the cathode has been simulated by Monte Carlo method. Y2O3–Mo cathode has the largest penetration depth and escape depth, which could be attributed to the highest secondary electron emission yield of the cathode. The content of La2O3 on the cathode surface is higher than that in the inner part down to the surface about 13 nm. The secondary emission process mainly occurs in La2O3.

Nitrogen and sulfur co-doped SrTiO3 was prepared by high energy grinding of the mixture of SrTiO3 and thiourea. A new band gap in visible light region (522 nm) corresponding to 2.37 eV could be formed by the co-doping. The photocatalytic activity for nitrogen monoxide oxidation of SrTiO3 in visible light region especially in the long wavelength range (λ > 510 nm) could be improved greatly. Under the irradiation of light with wavelength larger than 510 nm, the photocatalytic activity of nitrogen and sulfur co-doped SrTiO3 was 10.9 times greater than that of pure SrTiO3. The high visible light photocatalytic activity of this substance may be due to the formation of a new band gap that enables to absorb visible light effectively. The nitrogen and sulfur co-doped SrTiO3 exhibited higher NO elimination capability than pure SrTiO3 both in visible light range and near ultraviolet range. When the light was turned off, NO concentration returned to its initial level of 1 ppm within 10 min, indicating that the light energy is necessary for the oxidation of NO, i.e., NO was photocatalytically eliminated.

Sc2O3–W matrix cathodes have been prepared by using a liquid–liquid doping method combined with high-temperature sintering. The microstructure and physical behavior of active substances of scandia-doped tungsten matrix and impregnated cathode has been studied by SEM and AES methods. The results show that the matrix has a homogeneous structure composed of W grains with spherical shape and superfine Sc2O3 particles dispersed uniformly over and among W grains. After impregnation, this Sc-type impregnated cathode has high emission capability. Space-charge-limited current density could reach 52 A/cm2 at 850 °Cb. The high emission results from a Ba–Sc–O active layer with a thickness of about 80 nm, which is formed at the cathode surface during the activation period. Both the decrease of the thickness of active surface layer and the decrease of the content of Sc at the surface could lead to the degradation of current density during operation.

The paper describes the preparation and emission property of scandia and Re doped tungsten matrix impregnated cathode. By an easy and reproducible way, solid–liquid doping combined with two-step reduction, powders of tungsten particles covered with scandium oxide were obtained. Compared with scandia mixed tungsten powders prepared by mechanically mixing, scandia and rhenium doped tungsten powders had smaller particle size, for example, scandia (3 wt%) and Re (5 wt%) doped tungsten powders had the average size of about 50 nm in diameter. Based on this kind of powder, scandia and Re doped tungsten matrix with the sub-micrometer sized tungsten grains and a more uniform distribution of Sc2O3 were obtained in this paper. Scandia and Re doped tungsten matrix impregnated cathode had shown excellent emission property and good emission uniformity. The space charge limited current densities of more than 58A/cm2 at 900 °Cb could be obtained and the work function of this cathode was as low as 1.18 eV.

Fibrous SrTiO3 particles were prepared by a hydrothermal reaction method using strontium hydroxide octahydrate and protonic layered tetratitanate as raw materials. The samples were characterized by X-ray diffraction, X-ray photoelectron spectrometer, scanning electron microscopy, nitrogen adsorption–desorption isotherm measurements and diffusion reflectance spectra. SrTiO3 existed as two different morphologies of particles, i.e., fibrous particles and nanosized particles which attached to the surface of former ones. SrTiO3 seemed to be formed by two different ways. One way is a direct reaction between H2Ti4O9 and Sr(OH)2 and the other is a two-step reaction involving transformation of H2Ti4O9 to monoclinic TiO2 followed by a reaction with Sr(OH)2. Fibrous nitrogen doped SrTiO3, which exhibited excellent visible light responsive photocatalytic activity, was prepared by the heat treatment of fibrous SrTiO3 under the flow of ammonia gas at 600 °C for 3 h. Under the irradiation of light with wavelengths larger than 400 and 290 nm, the photocatalytic activities of fibrous SrTiO3 were 2.4 and 1.3 times greater than those of spherical SrTiO3 prepared by the solid-state reaction.

Fibrous SrTiO3 particles with nanosized crystals on the surface were prepared by hydrothermal reaction method using strontium hydroxide octahydrate and protonic layered tetratitanate as raw materials. SrTiO3 could be formed by two different ways simultaneously, one way is direct reaction between H2Ti4O9 and Sr(OH)2 and the other is two steps reaction involving transformation of H2Ti4O9 to monoclinic TiO2 and reaction between TiO2 and Sr(OH)2. The photocatalytic activity of fibrous SrTiO3 near ultraviolet light range (λ > 290 nm) was 1.5 times greater than that of SrTiO3 powder.

H2Ti4O9 nanocrystals with high specific surface areas were prepared by delamination and reassembly process through a way of ball milling combined with ion exchange reaction. The samples were characterized by X-ray powder diffraction, transmission electron microscopy, chemical analysis, thermal analysis, N2 adsorption-desorption isotherm, and absorption spectrum. The crystallites of Ti4O92− in the form of titania nanosheets has lateral size less than 50 nm. The specific surface area of H2Ti4O9 nanocrystals depends on pH value of reassembling solution and ball milling time. H2Ti4O9 nanocrystals prepared by ball-milling of K2Ti4O9 for 2 h and suspending in 1 M HCl followed by precipitation at pH 8 had the specific surface area of 328.4 m2 g−1 which was about 16 times larger than the fibrous H2Ti4O9 prepared by treating original K2Ti4O9 without ball-milling in 1 M HCl.H2Ti4O9 nanocrystals precipitated by milling K2Ti4O9 for 2 h and exfoliating in 1 M HCl followed by adjusting solution pH at 4 has nanosheets of lateral dimensions about 50 nm.

•MnNb2O6 nanosheets are crystallized by a surface capping route of sulfonate groups.•Oxalic acid on MnNb2O6 nanosheets forms an excited surface complex hybrid layer.•Surface activation enhances visible-light induced reduction of Cr(VI) into Cr(III).MnNb2O6 nanosheets (P-MNOs) is selectively crystallized by using surface capping ligand with functional sulfonate group (sodium dodecyl benzene sulphonate), which binds to the (131) surface of MnNb2O6 inducing the morphology-controlled crystallization of MnNb2O6 materials. Surface modification of photoactive P-MNOs with electron-rich oxalic acid ligands establishes an excited surface complex layer on phase-pure P-MNO as evidenced by spectroscopic analyses (FT-IR, UV–vis, Raman, PL, etc.), and thus more efficiently photocatalyzes the reduction of Cr(VI) into Cr(III) than solely P-MNOs or oxalic acid under visible light (λ > 420 nm) via a ligand-to-metal interfacial electron transfer pathway. However, the interaction between oxalic acid and MnNb2O6 is highly dependent upon the morphology of solid MnNb2O6 substrate due to the higher surface-area-to-volume ratio and higher surface activity of (131) planes in the sheet-like morphology. This study could assist the construction of stable niobate material systems to allow a versatile solid surface activation for establishing more energy efficient and robust catalysis process under visible light.Visible light driven photoreduction of Cr(VI) over MnNb2O6 nanosheets is enhanced via oxalic acid surface complex to generate activation layer.

Highly efficient photo-generated carrier transfer is one of the key factors in determining the performance of organic–inorganic hybrid perovskite solar cells (PSCs). Here, we demonstrate a strategy for improved hole transfer and collection by employing a composite hole transporting material (HTM) consisting of free standing Ni nanobelts dispersed in the widely used 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). It is found that power conversion efficiency (PCE) and ambient stability of mesoscopic PSCs have been improved. To be more specific, in order to prevent significant charge recombination induced by direct contact of the metal Ni with a perovskite absorber, a spiro-OMeTAD intermediate layer was spin-coated on the CH3NH3PbI3 layer prior to the sequentially deposited layers of Ni nanobelts and spiro-OMeTAD. With this architecture, the optimized PSC achieved a champion PCE of 16.18% with a short-circuit current density (Jsc) of 21.64 mA cm−2, an open-circuit voltage (Voc) of 1.02 V, and a fill factor (FF) of 73.3% under reverse scanning. Despite the small J–V hysteresis, a higher stabilized efficiency up to 14.47% near the maximum power point could be reached for the device fabricated with 1.8 mg mL−1 Ni nanobelts compared with the pristine one (12.05%). However in the presence of highly hygroscopic lithium-bis(trifluoromethane) sulfonimide (Li-TFSI), PSCs in conjunction with Ni nanobelts present an impressively favorable ambient stability with an observed PCE retention rate of over 85% after 4-week storage with exposure to ambient air without any encapsulation.

Herein we describe the mechanism of crystallization of Al3+ with amorphous TiO2 on a TiO2 film, and found that the resultant Al2TiO5 was able to improve the average efficiency of planar perovskite solar cells (PSCs) from 15.4 to 17.2%. The electron lifetime in these Al-PSCs was about 3 times longer than that in unmodified PSCs. The O 1s X-ray photoelectron spectrum of the TiO2/CH3NH3PbI3 interface indicated that the oxygen vacancy or defect peak decreased by more than 31% on modifying the interface with Al2TiO5. The stability of the PSCs was improved substantially: Al-PSCs had still 88% of their initial value after 1440 hours, while the efficiency of the reference PSCs decreased to 68% of their initial value.

TiO2 mesoporous nanoparticles (NPs) doped with yttrium (Y) ions are fabricated via an environmentally friendly and facile solvothermal method to serve as a photoanode for dye sensitized solar cells (DSSCs). X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and N2 adsorption–desorption tests are used to characterize the influence of yttrium dopant on the properties of TiO2 NPs. The prepared Y-doped TiO2 NPs show the anatase phase and exhibit Ti–O–Y bonds. The photovoltaic performance is primarily associated with the morphological parameters of the NPs. At the optimum Y concentration of 3 at%, the short circuit current density increased from 13.20 to 15.74 mA cm−2, full sun solar power conversion efficiencies increased from 6.09% up to 7.61% as compared to the blank DSSC.

Hierarchical WO3 hydrates have been synthesized via an ion exchange method using Na2WO4·2H2O as a precursor. The morphologies and phase structures of WO3 hydrates can be controlled by tuning the concentration of Na2WO4·2H2O solution. The as-synthesized urchin-like WO3·0.33H2O and flower-like WO3·H2O possess high specific surface area and numerous adsorption functional groups, such as WO and O–H bonds, on the surface. These characteristics result in excellent adsorption performance for both organic dyes and heavy metal ions from wastewater. The maximum uptake capacities of the urchin-like WO3·0.33H2O for methylene blue and Pb2+ are 247.3 and 248.9 mg g−1, respectively and those of the flower-like WO3·H2O are 117.8 and 315.0 mg g−1, respectively. The formation mechanism of such hierarchical mesoporous urchin-like WO3·0.33H2O and adsorption mechanism are studied in this paper.

We report the design and synthesis of two hematite (α-Fe2O3)-based nanomaterials based on effective hydrothermal conversion of chemically metastable K1.33Mn8O16 nanowires (KWs) in Fe(NO3)3 aqueous solution. Insights are gained into the functions of sodium dodecyl benzene sulfonate (SDBS) and the mechanisms for generating large quantities of α-Fe2O3 hollow structures (FHSs) and K1.33Mn8O16@α-Fe2O3 heterostructured nanowires (KFHWs) in solution phase. The controllable growth dynamics allows convenient control over the morphology and production of the hematite-based nanostructures. Adsorption experiments indicate that the resulting hematite-based materials are powerful nanosorbents for swift removal of Congo red from wastewater at room temperature. The adsorption kinetics and adsorption isotherm are also investigated and the findings indicate that the as-prepared KFHW and FHS hold great potential as environmentally friendly filter materials for water purification and organic waste removal.