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Solar-to-chemical energy conversion via heterogeneous photocatalysis is one of the sustainable approaches to tackle the growing environmental and energy challenges. Among various promising photocatalytic materials, plasmonic-driven photocatalysts feature prominent solar-driven surface plasmon resonance (SPR). Non-noble plasmonic metals (NNPMs)-based photocatalysts have been identified as a unique alternative to noble metal-based ones due to their advantages like earth-abundance, cost-effectiveness, and large-scale application capability. This review comprehensively summarizes the most recent advances in the synthesis, characterization, and properties of NNPMs-based photocatalysts. After introducing the fundamental principles of SPR, the attributes and functionalities of NNPMs in governing surface/interfacial photocatalytic processes are presented. Next, the utilization of NNPMs-based photocatalytic materials for the removal of pollutants, water splitting, CO2 reduction, and organic transformations is discussed. The review concludes with current challenges and perspectives in advancing the NNPMs-based photocatalysts, which are timely and important to plasmon-based photocatalysis, a truly interdisciplinary field across materials science, chemistry, and physics. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSC) are intensively studied due to their low-cost processing and high light-to-electricity conversion efficiency. However, the difficulty of the large scale fabrication hinders their practical applications, and the structure tuning of the nanomaterials to optimize PSC is still challenging. In this study, we fabricate nanosheet-based PSCs using mesoscopic TiO 2 nanosheets (NS) and p-type NiO nanosheets (NS) as electron transport material (ETM) and inorganic hole transport material (HTM), respectively. Furthermore, as the counter electrode (CE), carbon black/graphite can be applied by screen printing process to fabricate PSCs with the TiO 2 /ZrO 2 /NiO/carbon (CH 3 NH 3 PbI 3 ) structure. The nanosheet-based PSC with printable carbon counter electrode shows a promising conversion efficency of 7.50%, significantly higher than the value of 6.40% of the device using the HTM of NiO nanoparticles (NP). The electrochemical impedance analysis exhibits that NS structured PSC can decrease the electron recombination effectively and enhance the collection of the charge carriers. This research presents a novel nanostructured PSC with printable carbon counter electrode, which is promising for PSC engineering technique and large scale manufacture with low cost. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen production from water splitting is of promising potential to resolve the energy shortage and environmental concerns. During the past decade, carbon materials have shown great ability to enhance the photocatalytic hydrogen-production performance of semiconductor photocatalysts. This review provides a comprehensive overview of carbon materials such as CNTs, graphene, C 60 , carbon quantum dots, carbon fibers, activated carbon, carbon black, etc. in enhancing the performance of semiconductor photocatalysts for H 2 production from photocatalytic water splitting. The roles of carbon materials including supporting material, increasing adsorption and active sites, electron acceptor and transport channel, cocatalyst, photosensitization, photocatalyst, band gap narrowing effect are explicated in detail. Also, strategies for improving the photocatalytic hydrogen-production efficiency of carbon-based photocatalytic materials are discussed in terms of surface chemical functionalization of the carbon materials, doping effect of the carbon materials and interface engineering between semiconductors and carbon materials. Finally, the concluding remarks and the current challenges are highlighted with some perspectives for the future development of carbon-based photocatalytic materials. [ABSTRACT FROM AUTHOR]

As a green and sustainable technology, semiconductor-based heterogeneous photocatalysis has received much attention in the last few decades because it has potential to solve both energy and environmental problems. To achieve efficient photocatalysts, various hierarchical semiconductors have been designed and fabricated at the micro/nanometer scale in recent years. This review presents a critical appraisal of fabrication methods, growth mechanisms and applications of advanced hierarchical photocatalysts. Especially, the different synthesis strategies such as two-step templating, in situ template-sacrificial dissolution, self-templating method, in situ template-free assembly, chemically induced self-transformation and post-synthesis treatment are highlighted. Finally, some important applications including photocatalytic degradation of pollutants, photocatalytic H2 production and photocatalytic CO2 reduction are reviewed. A thorough assessment of the progress made in photocatalysis may open new opportunities in designing highly effective hierarchical photocatalysts for advanced applications ranging from thermal catalysis, separation and purification processes to solar cells. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen evolution under visible light is of great potential for renewable energy development. In this work, unalloyed Au/PtO nanoparticle (NP) co-modified graphitic carbon nitride (g-C 3 N 4 ) photocatalyst is fabricated through a simple photodeposition method. The obtained g-C 3 N 4 composites with co-existed Au and PtO cocatalysts exhibit a considerable enhancement in the photocatalytic hydrogen evolution activity and possess good stability during cycling experiments. The optimal Au–PtO/g-C 3 N 4 photocatalyst shows a H 2 production rate of 16.9 μmol h −1 , which exceeds that of PtO/g-C 3 N 4 and Au/g-C 3 N 4 by a factor of 1.5 and 10.6, respectively. Further characterizations demonstrate that the synergetic action of electron-sink and catalytic effects of PtO along with surface plasmon resonance (SPR) effect of Au NPs, greatly improves the photocatalytic performance of g-C 3 N 4 under visible light. Our study should bring in new insight into the design of effective g-C 3 N 4 -based photocatalysts for solar-to-fuel conversion. [ABSTRACT FROM AUTHOR]

Photocatalytic conversion of CO 2 into hydrocarbon fuels using semiconductor photocatalysts has attracted great attention, which is considered as a promising approach to resolve the energy shortage and greenhouse effect. In this work, amine-functionalized g-C 3 N 4 was prepared by heating urea at 500 °C, with a subsequent functionalization treatment by monoethanolamine solution. The amine-functionalized g-C 3 N 4 exhibits improved photocatalytic performance on CO 2 photoreduction, which can be attributed to the enhanced CO 2 adsorption capacity. The optimized photocatalyst shows much higher CO 2 conversion efficiency as compared to pure g-C 3 N 4 under the same conditions, with a CH 4 -production rate of 0.34 μmol h −1 g −1 and CH 3 OH-production rate of 0.28 μmol h −1 g −1 . This work demonstrates the surface amine functionalization is a successful strategy to improve the CO 2 adsorption capacity of g-C 3 N 4 for the enhancement of CO 2 photoreduction activity. [ABSTRACT FROM AUTHOR]

Single-crystalline anatase TiO2 nanocubes with exposed {100} and {001} facets, prepared by hydrothermal and calcination methods, display especially high photocatalytic activity toward CO2 reduction to methane and methanol, due to the synergistic effects of better crystallization, a more negative conduction band position and co-exposed {100} and {001} facets. [ABSTRACT FROM AUTHOR]

Mesoporous AlOOH with deposited Pt (Pt/AlOOH) catalyst was prepared by combining the microemulsion-assisted synthesis of AlOOH nanoflakes with NaBH 4 -reduction of Pt precursor, and exhibited a remarkable catalytic activity as well as stability for elimination of formaldehyde (HCHO) vapor at room temperature. As compared to Pt deposited on calcined AlOOH (Pt/AlOOH-c), Pt on a commercial Al 2 O 3 (Pt/c-Al 2 O 3 ) and Pt on P25 (Pt/TiO 2 ), the Pt/AlOOH nanoflakes showed the highest catalytic activity toward decomposition of HCHO at room temperature. The excellent performance of Pt/AlOOH nanoflakes could be attributed to the abundance of surface hydroxyls, high dispersion of Pt nanoparticles, excellent adsorption performance of AlOOH, and its high specific surface area and large pore volume. The mechanism of HCHO decomposition was investigated with respect to the behavior of adsorbed intermediates on Pt/AlOOH surface at room temperature using in situ DRIFTS. The result suggests that surface formate is the main reaction intermediate during the HCHO oxidation and it could be directly oxidized to CO 2 in the presence of O 2 . By taking advantage of high adsorption affinity of AlOOH nanoflakes and excellent catalytic activity of Pt nanoparticles toward HCHO it was possible to design a superior nanostructured catalyst for room temperature decomposition of HCHO. This strategy can be also used to fabricate novel nanostructured catalysts for advanced applications such as environmental remediation. [ABSTRACT FROM AUTHOR]

Highlights: [•] CdS with various morphologies prepared by solvothermal method. [•] Solvent influencing morphology and photocatalytic H2-production activity of CdS. [•] The highest H2-production activity observed for CdS nanowires. [Copyright &y& Elsevier]

To overcome the drawbacks of high air resistance and the need to be pressed into tablets or attached to other big-block supports for powder catalysts in the application of air purification, a mat-like hierarchically porous TiO2 nanofibers (TF) decorated with Pt nanoparticles (NPs) catalyst (Pt/TF) was synthesized by dipping the hierarchically porous TF mat fabricated by electrospinning into an H2PtCl6 solution followed by NaBH4 reduction. Such a mat-like catalyst has a smaller air resistance than a powder catalyst because of its hierarchical macro-/mesoporous structure and can be used directly in air-purification systems because of its larger size. In addition, the as-prepared Pt/TF catalyst showed enhanced catalytic activity compared to a Pt-NP-decorated commercial TiO2 (P25) catalyst in the decomposition of formaldehyde at room temperature because of its accessible Pt NPs and hierarchical porous structure that facilitates the diffusion of reactants and products. This work will provide some new insights into the design and fabrication of advanced catalysts for indoor air purification. [ABSTRACT FROM AUTHOR]

Highlight: [•] Visible-light-responsive plasmonic Ag@AgCl composite immobilized on titanate nanowire films was prepared. [•] The as-prepared films exhibit higher visible-light photocatalytic performance for the degradation of MO than P25. [•] The samples also show enhanced photocatalytic activity for the degradation of RhB and phenol. [•] Highly reactive species like Cl0 and O2 − is responsible for the photoreactivity. [Copyright &y& Elsevier]

Highlights: [•] The photocatalytic mechanism of visible-light response N S codoped anatase TiO2 was first investigated by the first-principles. [•] The O-poor growth condition is beneficial to the formation of N S codoped anatase TiO2. [•] The bent and flat impurity levels were the separation and combination centers of photogenerated electrons and holes, respectively. [•] The dominant oxidant species during photocatalytic reaction for N S codoped TiO2 was hole and OH radical instead of O2 − ion. [ABSTRACT FROM AUTHOR]

Ni(OH)2/SiO2 composites with hierarchical flake-like nanostructures were synthesized using water-in-oil microemulsion and characterized by X-ray diffraction, thermogravimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption, and X-ray photoelectron spectroscopy. The as-prepared hierarchical porous Ni(OH)2/SiO2 composites show an excellent performance for formaldehyde (HCHO) removal in air at an ambient temperature. It was found that the aging time had a significant impact on the pore structure, surface area and HCHO adsorption. The Ni(OH)2/SiO2 composite aged for 4 h in the presence of tetraethyl orthosilicate (TEOS) exhibited a relatively high HCHO adsorption capacity as well as good recyclability compared with Ni(OH)2, attributed to a relatively large BET surface area, an optimal pore size, a suitable proportion between Ni(OH)2 and SiO2, and a synergistic effect between Ni(OH)2 and SiO2. The results from this work not only demonstrate that hierarchical porous Ni(OH)2/SiO2 composites can act as an efficient adsorbent toward HCHO in air, but suggest a new route for the rational design of cost-effective, high-performance and environmentally benign adsorbents for indoor air cleanup. [ABSTRACT FROM AUTHOR]

Mesoporous ferrihydrite/SiO2 composites were synthesized according to a water-in-oil microemulsion method and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry, nitrogen-adsorption/desorption, and by X-ray photoelectron spectroscopy. The as-prepared porous ferrihydrite/SiO2 composites showed an excellent adsorption performance for formaldehyde (HCHO) removal from indoor air at ambient temperature. It was found that the aging time during the synthesis had a significant impact on the pore structure, surface area, and HCHO adsorption of these materials. The ferrihydrite/SiO2 composite that was aged for 3 h in the presence of tetraethyl orthosilicate (TEOS) exhibited a relatively high HCHO adsorption capacity, as well as good recyclability, which was attributed to a relatively large BET surface area, optimal pore size, a suitable Si/Fe atomic ratio, and a synergistic effect between ferrihydrite and SiO2. This work not only demonstrates that porous ferrihydrite/SiO2 composites can act as an efficient adsorbent toward HCHO, but suggests a new route for the rational design of cost-effective and environmentally benign adsorbents with high performance for indoor air purification. [ABSTRACT FROM AUTHOR]

Abstract: Carbon quantum dots (CDs) with an average size of less than 10nm were prepared by ionic liquid-assisted electrochemical exfoliation of graphite electrode, and developed as photoluminescence (PL) and electrochemiluminescence (ECL) probes for efficient detecting Ru(bpy)3 2+ in the solution based on the quenching of the PL emission of CDs and enhanced ECL of Ru(bpy)3 2+, respectively. The PL and ECL probes exhibited a detection limit of 0.72 and 0.43μM, respectively. The PL and ECL properties of CDs and Ru(bpy)3 2+ will provide a new route to study the novel materials and broaden the use of them in analyte detection. [Copyright &y& Elsevier]

The effects of a room temperature ionic liquid, 1-butyl-3-methylimidazolium terafluoroborate ([Bmim]BF), on the photocatalytic performance of Degussa P25 TiO were investigated. Also, the photocatalysis mechanism was systematically analyzed by conducting different reactive radical trapping experiments. The results showed that photogenerated electrons were the main reactive species involved in the photocatalytic degradation of methyl orange (MO), while •OH radicals and photogenerated holes played an important role in the photocatalytic decomposition of rhodamine B (RhB). The addition of ionic liquid (IL) could slightly enhance the photocatalytic degradation rate of MO because adsorption of [Bmim] ions on the TiO surface not only enhanced traping and transfer of photogenerated electrons, but also facilitated adsorption of negatively charged MO. On the contrary, IL suppressed the degradation rate of RhB because [Bmim] on the TiO surface not only hindered the access of positively charged RhB to TiO, but also restricted the diffusion of positively charged holes to the TiO/solution interface. [ABSTRACT FROM AUTHOR]

Exploiting advanced photocatalysts under visible light is of primary significance for the development of environmentally relevant photocatalytic decontamination processes. In this study, the ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate, was employed for the first time as both a structure-directing agent and a dopant for the synthesis of novel fluorinated B/C-codoped anatase TiO2 nanocrystals (TIL) through hydrothermal hydrolysis of tetrabutyl titanate. These TIL nanocrystals feature uniform crystallite and pore sizes and are stable with respect to phase transitions, crystal ripening, and pore collapse upon calcination treatment. More significantly, these nanocrystals possess abundant localized states and strong visible-light absorption in a wide range of wavelengths. Because of synergic interactions between titania and codopants, the calcined TIL samples exhibited high visible-light photocatalytic activity in the presence of oxidizing Rhodamine B (RhB). In particular, 300 °C-calcined TIL was most photocatalytically active; its activity was much higher than that of TiO1.98N0.02 and reference samples (TW) obtained under identical conditions in the absence of ionic liquid. Furthermore, the possible photocatalytic oxidation mechanism and the active species involved in the RhB degradation photocatalyzed by the TIL samples were primarily investigated experimentally by using different scavengers. It was found that both holes and electrons, as well as their derived active species, such as .OH, contributed to the RhB degradation occurring on the fluorinated B/C-codoped TiO2 photocatalyst, in terms of both the photocatalytic reaction dynamics and the reaction pathway. The synthesis of the aforementioned novel photocatalyst and the identification of specific active species involved in the photodegradation of dyes could shed new light on the design and synthesis of semiconductor materials with enhanced photocatalytic activity towards organic pollutants. [ABSTRACT FROM AUTHOR]

Design and preparation of efficient artificial photosynthetic systems for harvesting solar energy by production of hydrogen from water splitting is of great importance from both theoretical and practical viewpoints. ZnS-based solid solutions have been fully proved to be an efficient visible-light driven photocatalysts, however, the H2-production rate observed for these solid solutions is far from exciting and sometimes an expensive Pt cocatalyst is still needed in order to achieve higher quantum efficiency. Here, for the first time we report the high solar photocatalytic H2-production activity over the noble metal-free reduced graphene oxide (RGO)-ZnxCd1–xS nanocomposite prepared by a facile coprecipitation-hydrothermal reduction strategy. The optimized RGO-Zn0.8Cd0.2S photocatalyst has a high H2-production rate of 1824 μmol h–1 g–1 at the RGO content of 0.25 wt % and the apparent quantum efficiency of 23.4% at 420 nm (the energy conversion efficiency is ca. 0.36% at simulated one-sun (AM 1.5G) illumination). The results exhibit significantly improved photocatalytic hydrogen production by 450% compared with that of the pristine Zn0.8Cd0.2S, and are better than that of the optimized Pt-Zn0.8Cd0.2S under the same reaction conditions, showing that the RGO-Zn0.8Cd0.2S nanocomposite represents one of the most highly active metal sulfide photocatalyts in the absence of noble metal cocatalysts. This work creates a green and simple way for using RGO as a support to enhance the photocatalytic H2-production activity of ZnxCd1–xS, and also demonstrates that RGO is a promising substitute for noble metals in photocatalytic H2-production. [ABSTRACT FROM AUTHOR]

Abstract: Graphene, a single layer of graphite, possesses a unique two-dimensional structure, high conductivity, superior electron mobility and extremely high specific surface area, and can be obtained on a large scale at low cost. Thus, it has been regarded as an excellent catalyst support. Recently, graphene-based semiconductor photocatalysts have attracted more attention due to their enhanced photocatalytic activity. In this work, hierarchical macro/mesoporpous TiO2–graphene composites with low loadings (0–0.2wt.%) of graphene were first produced by a simple one-step hydrothermal method using tetrabutyl titanate as the titanium precursor. The prepared composite samples presented enhanced photocatalytic activity in photodegradation of acetone in air. Graphene content exhibited an obvious influence on photocatalytic activity and the optimal graphene addition content was determined. At the optimal graphene concentration (0.05wt.%), the prepared composites showed the highest photocatalytic activity, exceeding that of pure TiO2 and Degussa P-25 by a factor of 1.7 and 1.6, respectively. The enhanced photocatalytic activity is due to graphene as an excellent electron acceptor and transporter, thus reducing the recombination of charge carriers and enhancing the photocatalytic activity. The transient photocurrent response experiment further confirmed the transfer of photogenerated electrons from TiO2 to graphene and the suggested mechanism. [Copyright &y& Elsevier]

Abstract: Semiconductor photocatalysts are of great significance in solar energy conversion and environmental remediation. To overcome serious drawbacks of these materials with respect to narrow light-response range and low quantum efficiency, a variety of strategies have been developed in the past decades to enhance the light harvesting and excitation as well as the charge transfer against recombination. In particular, fluorination of semiconductor photocatalysts can be employed to modify their surface and bulk properties, and consequently, to enhance their photocatalytic performance. This review presents a comprehensive description of the F-mediated synthesis and unique properties of fluorinated semiconductor photocatalysts, in particular titanium dioxide (TiO2). The available strategies for the synthesis of fluorinated photocatalysts include post-synthesis fluorination and in-situ fluorination. Depending on the synthesis route and conditions, it is possible to control the chemical nature of incorporated fluorine (such as adsorbed fluoride and lattice-doped fluorine) and the fluoride-mediated crystal modification and organization, which often results in exceptional surface and bulk physicochemical properties, giving rise to unique photocatalytic properties. Significantly, the surface fluorination induces unusual adsorption behavior and interfacial charge transfer dynamics, directly affecting photocatalytic redox properties of the surface-fluorinated photocatalysts. The lattice fluorine-doping, sole or cooperative with other complementary co-dopants, introduces special localized electronic structures and surface defect states, accounting for the exceptional visible-light photoactivity of the fluorine-doped photocatalysts. Finally, recent advances in the synthesis and properties of fluorinated photocatalysts are summarized along with perspectives on further developments in this area of research. [Copyright &y& Elsevier]

Abstract: Novel electrocatalysts Au/TiO2 nanotube arrays (Au/TiO2NTs) were prepared by loading low-content(1.9at.%) of Au nanoparticles (AuNPs) onto highly ordered TiO2 nanotube arrays (TiO2NTs). Ethanol electrooxidation indicates that visible-light (λ>400nm) irradiation can significantly enhance the activity as well as resistpoisoning of Au/TiO2NTs electrocatalysts that are activated by plasmon resonance. Au/TiO2NTs catalysts calcinated at 300°C display the highest performance due to the strong synergistic interactions between TiO2 and Au NPs. The combination of visible-light irradiation with a controllable potential offers a new strategyfor enhancing the performance of anodes in direct ethanol fuel cell (DEFC). [Copyright &y& Elsevier]

Conventional titania photocatalysts possess good activity and stability, but require near-ultraviolet (UV) irradiation (about 4% of the solar spectrum) for effective photocatalysis, which severely limits their practical applications. Here we report the synthesis of new visible-light-driven Ni(OH)2-modified CdS nanorod-type composite photocatalysts by a simple precipitation method using CdS nanorods as a support and Ni(NO3)2 as a nickel hydroxide precursor. A special emphasis is placed on the effect of Ni(OH)2 content in this composite photocatalyst on the photocatalytic rate of H2 production in triethanolamine aqueous solutions under visible light irradiation. This study shows that the photocatalytic H2-production activity of CdS nanorods is significantly enhanced by modifying them with Ni(OH)2. The optimal Ni(OH)2 loading was found to be 23 mol%, which resulted in a visible-light H2-production rate of 5085 μmol h−1 g−1 corresponding to 28% quantum efficiency (QE) at 420 nm, exceeding that of pure CdS and 1wt% Pt loaded CdS nanorods by a factor of 145 and 1.3 times, respectively. This enhanced photocatalytic H2-production activity was achieved because the potential of Ni2+/Ni (Ni2+ + 2e− = Ni, E° = −0.23 V) is less negative than the conduction band (CB) (−0.7 V) of CdS, meanwhile this potential is more negative than the reduction potential of H+/H2 (2H+ + 2e− = H2, E° = 0.0 V), which favors the transfer of CB electrons from CdS to Ni(OH)2 and the reduction of Ni2+ to Ni0. The role of Ni0 is to help the charge separation and to act as a co-catalyst for water reduction, thus enhancing the photocatalytic H2-production activity. This work not only shows a possibility for the utilization of low cost Ni(OH)2 as a substitute for noble metal Pt in photocatalytic H2-production but also demonstrates its capability for the consumption of the pollutant triethanolamine, used as a sacrificial reagent in this process. [ABSTRACT FROM AUTHOR]

Abstract: Dye-sensitized solar cells (DSSCs) based on anatase TiO2 hollow spheres (TiO2HS)/multi-walled carbon nanotubes (CNT) nanocomposite films are prepared by a directly mechanical mixing and doctor blade method. The prepared samples are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV–vis absorption spectroscopy and N2 adsorption–desorption isotherms. The photoelectric conversion performances of the DSSCs based on TiO2HS/CNT composite film electrodes are also compared with commercial-grade Degussa P25 TiO2 nanoparticles (P25)/CNT composite solar cells at the same film thickness. The results indicate that the photoelectric conversion efficiencies (η) of the TiO2HS/CNT composite DSSCs are dependent on CNT loading in the electrodes. A small amount of CNT clearly enhances DSSC efficiency, while excessive CNT loading significantly lowers their performance. The former is because CNT enhance the transport of electrons from the films to FTO substrates. The latter is due to high CNT loading shielding the visible light from being adsorbed by dyes. [Copyright &y& Elsevier]

Abstract: Dye-sensitized solar cells (DSSCs) are fabricated based on double-layered composite films of TiO2 nanoparticles and hollow spheres. The photoelectric conversion performances of DSSCs based on nanoparticles/nanoparticles (PP), hollow spheres/hollow spheres (HH), hollow spheres/nanoparticles (HP), and nanoparticles/hollow spheres (PH) double-layered films are investigated, and their photo-electric conversion efficiencies are 4.33, 4.72, 4.93 and 5.28%, respectively. The enhanced performance of TiO2 nanoparticles/hollow spheres double-layered composite film solar cells can be attributed to the combined effect of following factors. The light scattering of overlayer hollow spheres enhances harvesting light of the DSSCs and the underlayer TiO2 nanoparticle layer ensures good electronic contact between film electrode and the F-doped tin oxide (FTO) glass substrate. Furthermore, the high surface areas and pore volume of TiO2 hollow spheres are respectively beneficial to adsorption of dye molecules and transfer of electrolyte solution. [Copyright &y& Elsevier]

In this work, fullerene modified TiO2nanocomposites (denoted as C60/TiO2) with low C60loadings (0–1.5 wt.%) have been prepared by a simple hydrothermal method using tetrabutylorthotitanate (TBOT, Ti(OC4H9)4) as the titanium precursor. The as-prepared C60/TiO2nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, UV-visible spectrophotometry, nitrogen adsorption, and X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy. The formation of hydroxyl radicals (OH) on the surface of UV-illuminated TiO2is probed by photoluminescence using terephthalic acid as a probe molecule. Our results have demonstrated that C60molecules can be dispersed as a monolayer onto bimodal mesoporous TiO2viacovalent bonding. The photocatalytic oxidation rate of gas-phase acetone over C60/TiO2nanocomposites is greater than that over pure TiO2, commercial Degussa P25 (P25) and C60–TiO2counterparts prepared by simple impregnating mixing. In particular, 0.5 wt.% C60/TiO2nanocomposites show the greatest photocatalytic activity with the rate constant kexceeding that of P25 by a factor of 3.3. Based on the results of the current study, we propose that C60molecules doped onto TiO2act as “electron acceptors” responsible for the efficient separation of photogenerated charge carriers and the enhancement of photocatalytic activity. The proposed mechanism for the observed photocatalytic performance of C60/TiO2nanocomposites is further corroborated by experiments on hydroxyl radical and transient photocurrent response. [ABSTRACT FROM AUTHOR]

Abstract: Hydroxyl radicals ( OH) have been deemed to be the major active species during the photocatalytic oxidation reaction. In this study, OH produced on various semiconductor photocatalysts in aqueous solution under Xenon lamp irradiation was quantitatively investigated by the photoluminescence (PL) technique using coumarin (COU) as a probe molecule. The results indicated that the formation rate of OH on the surface of irradiated commercial Degussa P25 (P25) was much higher than that of other semiconductor. The pH values of the solution and phase structure of TiO2 significantly influenced the production rate of OH. The acidic pH environment of the solutions and bi-phase structure (anatase and rutile) of TiO2 were beneficial to enhancing the formation rate of OH. In addition, the formation rate of OH on anatase TiO2 and P25 was much faster than that of OH on the other semiconductors (such as rutile TiO2, ZnO, WO3, CdS, Bi2WO4 and BiOCl, etc.). A new concept “OH-index” was first proposed to compare photocatalytic activity of photocatalysts, which would provide new insight into the investigation of semiconductor photocatalysts. [Copyright &y& Elsevier]

Abstract: Efficient hydrogen production and decomposition of glycerol were achieved on CuO-modified titania (CuO–TiO2) photocatalysts in glycerol aqueous solutions. CuO clusters were deposited on the titania surface by impregnation of Degussa P25 TiO2 powder (P25) with copper nitrate followed by calcination. The resulting CuO–TiO2 composite photocatalysts were characterized by X-ray diffraction (XRD), UV–visible spectrophotometry, X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The low-power ultraviolet light emitting diodes (UV-LED) were used as the light source for photocatalytic H2-production reaction. A detailed study of CuO effect on the photocatalytic H2-production rates showed that CuO clusters can act as an effective co-catalyst enhancing photocatalytic activity of TiO2. The optimal CuO content was found to be 1.3wt.%, giving H2-production rate of 2061μmolh−1 g−1 (corresponding to the apparent quantum efficiency (QE) of 13.4% at 365nm), which exceeded the rate of pure TiO2 by more than 129 times. The quantum size effect of CuO clusters is deemed to alter its energy levels of the conduction and valence band edges in the CuO–TiO2 semiconductor systems, which favors the electron transfer and enhances the photocatalytic activity. This work shows not only the possibility of using CuO clusters as a substitute for noble metals in the photocatalytic H2-production but also demonstrates a new way for enhancing hydrogen production activity by quantum size effect. [Copyright &y& Elsevier]

Abstract: Preparation of anatase TiO2 with high themal stability is of great importance for its environmental application. In this work, TiOF2 was first synthesized by a simple microwave-assisted hydrothermal route using tetrabutyl titanate and hydrofluoric acid as precursors at 200°C for 20min. Then the resulted precipitates were calcined at different temperatures (300–1000°C) for 2h. The as-prepared samples were characterized by X-ray diffraction, Raman spectrum, scanning electron microscopy, N2 adsorption–desorption isotherms and X-ray photoelectron spectroscopy. The photocatalytic activity was evaluated using Brilliant Red X3B, an anionic azo dye, as the target organic molecule under UV light irradiation. The results showed that the prepared TiOF2 exhibited weak or no photocatalytic activity. The phase transformation of TiOF2 to anatase TiO2 occurred at about 300°C. The prepared anatase TiO2 from TiOF2 showed very high thermal stability and the anatase-to-rutile phase transformation temperature was up to 1000°C. Fluoride ions played an important role in the improvement of thermal stability of anatase TiO2 by strongly adsorbing on the crystal planes of anatase to stabilize the anatase structure. The 700°C-calcined sample showed the highest photocatalytic activity due to its relative good crystallization and high specific surface areas. [Copyright &y& Elsevier]

Abstract: Trifluoroacetic acid (TFA) modified TiO2 (TFA-TiO2) hollow microspheres were prepared by one-pot hydrothermal treatment of Ti(SO4)2 in the presence of TFA at 180°C for 12h. The prepared samples were characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption–desorption isotherms and Fourier transform infrared. The production rates of surface of UV-illuminated TiO2 were detected by a photoluminescence (PL) method using terephthalic acid (TA) as probe molecule. The photocatalytic activity was evaluated by the photocatalytic decomposition of acetone in air under UV light illumination. The results show that TFA not only induces the formation of hollow microspheres, but also enhances their crystallization. The molar ratios of TFA to Ti(SO4)2 (R) have a great influence on photocatalytic activity. When R is in the range of 0.5–5, the photocatalytic activity of the samples is higher than that of commercial Degussa P25 TiO2 powders (P25) and pure TiO2 samples. At R =2, the photocatalytic activity of the sample reaches the highest and exceeds that of P25 by a factor of more than two times. This is ascribed to the fact that the former has hollow interior and bimodal mesoporous shells enhancing harvesting of light and the transfer and transport of reactant and product molecules, also, the surface-adsorbed TFA can reduce the recombination of photo-generated electrons and holes. [Copyright &y& Elsevier]

Abstract: Bimodal nanocrystalline mesoporous TiO2 powders with highly photocatalytic activity were prepared by a hydrothermal method using tetrabutylorthotitanate as precursor, and then dried in microwave oven. The prepared samples were characterized by XRD, SEM, TEM, HRTEM and N2 adsorption–desorption measurement. The photocatalytic activity was evaluated by the photocatalytic degradation of acetone in air under UV light irradiation at room temperature. The effects of microwave drying on the microstructures and photocatalytic activity of the TiO2 powders were investigated and discussed. The results show that microwave drying not only promotes the growth of the pores but also greatly reduces the state of agglomeration within the powders. All the microwave-dried TiO2 powders show higher photocatalytic activity than Degussa P-25 (P25) and the TiO2 powders dried by conventional method. [Copyright &y& Elsevier]

Abstract: Highly ordered TiO2 nanotube arrays (TNs) are prepared by electrochemical anodization of titanium foil in a mixed electrolyte solution of glycerol and NH4F and then calcined at various temperatures. The prepared samples are characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The photocatalytic activity is evaluated by photocatalytic degradation of methyl orange (MO) aqueous solution under UV light irradiation. The production of hydroxyl radicals (e surface of UV-irradiated samples is detected by a photoluminescence (PL) technique using terephthalic acid (TA) as a probe molecule. The transient photocurrent response is measured by several on–off cycles of intermittent irradiation. The results show that low temperatures (below 600°C) have no great influence on surface morphology and architecture of the TNs sample and the prepared TNs can be stable up to ca. 600°C. At 800°C, the nanotube arrays are completely destroyed and only dense rutile crystallites are observed. The photocatalytic activity, formation rate of hydroxyl radicals and photocurrent of the TNs increases with increasing temperatures (from 300 to 600°C) due to the enhancement of crystallization. Especially, at 600°C, the sample shows the highest photocatalytic activity due to its bi-phase composition, good crystallization and remaining tubular structures. With further increase in the calcination temperature from 600 to 800°C, the photocatalytic activity rapidly decreases due to the vanishing of anatase phase, collapse of nanotube structures and decrease of surface areas. [Copyright &y& Elsevier]

Abstract: To study the synergistic effects of hollow structure and surface fluorination on the photoactivity of TiO2, TiO2 hollow microspheres were synthesized by a hydrolysis–precipitate method using sulfonated polystyrene (PS) as templates and tetrabutylorthotitanate (TBOT) as precursor, and then calcined at 500°C for 2h. The calcined samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N2 sorption. Photocatalytic activity was evaluated using reactive brilliant red X3B, an anionic organic dye, as a model pollutant in water. The results show that the photocatalytic activity of TiO2 hollow microspheres is significantly higher than that of TiO2 nanoparticles prepared in the same experimental conditions. At pH 7 and 3, the apparent rate constants of the former exceed that of the latter by a factor of 3.38 and 3.15, respectively. After surface fluorination at pH 3, the photoactivity of hollow microspheres and nanoparticles further increases for another 1.61 and 2.19 times, respectively. The synergistic effect of surface fluorination and hollow structure can also be used to prepare other highly efficient photocatalyst. [Copyright &y& Elsevier]

Abstract: Dye-sensitized solar cells (DSSCs) are fabricated based on hollow anatase TiO2 (HA-TiO2) spheres synthesized by a chemically induced self-transformation (CIST) strategy using urea as a base catalyst, whose walls are composed of anatase nanocrystals and exhibit hierarchical porosity. TiO2 hollow structured materials not only have low density, high specific surface areas, and hierarchically porous structures, but also exhibit high light-collection efficiency and fast motion of charge carriers. Effects of calcination temperatures on the performance of HA-TiO2 solar cells are investigated and discussed. With increasing calcination temperatures, the light–electricity conversion efficiencies (η) increase. At 600°C, HA-TiO2 cells reach the highest efficiency. The performances of HA-TiO2 cells are also compared with Degussa P-25 (P25) TiO2 nanoparticle cells at the same film thickness, and their optimal efficiencies at 600°C are 4.82 and 4.35%, respectively. The enhanced performance of HA-TiO2 cells is due to their high surface area and hierarchically nanoporous structures when compared with the nonporous TiO2 nanoparticles (P25). [Copyright &y& Elsevier]

Abstract: Bimodal mesoporous TiO2 microspheres with high photocatalytic activity were prepared by a hydrothermal method using titanium sulfate as precursor in the presence of urea. The results indicate that all prepared samples show bimodal pore-size distributions in the mesoporous region: smaller intra-aggregated pores with peak pore diameter of ca. 2nm and larger inter-aggregated pores with peak pore diameter of ca. 12.5nm. The molar ratio of urea to Ti(SO4)2 (R u) has an obvious influence on the morphology, microstructure and photocatalytic activity of TiO2. With increasing R u, specific surface areas and porosity increase, contrarily, the crystallite size and relative anatase crystallinity decrease. The photocatalytic activity first increases with R u. At R u =2.0, the photocatalytic activity reaches the highest and is obviously higher than that of Degussa P25. With further increasing R u, the photocatalytic activity decreases. The formation rate of hydroxyl radicals during photocatalysis has a positive correlation with the photocatalytic activity. [Copyright &y& Elsevier]

Abstract: Dye-sensitized solar cells (DSSCs) are fabricated based on ordered titanate nanotube (TNT) films obtained by electrophoretic deposition (EPD) method. Calcination temperatures show a great influence on the performance of TNT solar cells. At 300°C, the cells exhibit very low photo-electric conversion efficiency. At 400°C, the efficiency obviously increases. At 600°C, the cells show the highest efficiency, which is higher than the efficiency of the cells made from commercial-grade Degussa P25 TiO2 nanoparticles (P25). [Copyright &y& Elsevier]

Abstract: Hierarchically flower-like tungsten trioxide assemblies were fabricated on a large scale by a simple hydrothermal treatment of sodium tungstate in aqueous solution of nitric acid. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption–desorption measurements. The photocatalytic activity was evaluated by photocatalytic decolorization of rhodamine B aqueous solution under visible-light irradiation. It was found that the three-dimensional tungsten trioxide assemblies were constructed from two-dimensional layers, which were further composed of a large number of interconnected lathy nanoplates with different sizes. Such flower-like assemblies exhibited hierarchically porous structure and higher visible-light photocatalytic activity than the samples without such hierarchical structures due to their specific hierarchical pores that served as the transport paths for light and reactants. After five recycles for the photodegradation of RhB, the catalyst did not exhibit any great loss in activity, confirming hierarchically flower-like tungsten trioxide was stability and not photocorroded. This study may provide new insight into environmentally benign preparation and design of novel photocatalytic materials and enhancement of photocatalytic activity. [Copyright &y& Elsevier]

Abstract: Fe-doped TiO2 (Fe-TiO2) nanorods were prepared by an impregnating-calcination method using the hydrothermally prepared titanate nanotubes as precursors and Fe(NO3)3 as dopant. The as-prepared samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption–desorption isotherms and UV–vis spectroscopy. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air under visible-light irradiation. The results show that Fe-doping greatly enhance the visible-light photocatalytic activity of mesoporous TiO2 nanorods, and when the atomic ratio of Fe/Ti (R Fe) is in the range of 0.1–1.0%, the photocatalytic activity of the samples is higher than that of Degussa P25 and pure TiO2 nanorods. At R Fe =0.5%, the photocatalytic activity of Fe-TiO2 nanorods exceeds that of Degussa P25 by a factor of more than two times. This is ascribed to the fact that the one-dimensional nanostructure can enhance the transfer and transport of charge carrier, the Fe-doping induces the shift of the absorption edge into the visible-light range with the narrowing of the band gap and reduces the recombination of photo-generated electrons and holes. Furthermore, the first-principle density functional theory (DFT) calculation further confirms the red shift of absorption edges and the narrowing of band gap of Fe-TiO2 nanorods. [Copyright &y& Elsevier]

Abstract: Mesoporous titania nanospheres with high specific surface area and good photocatalytic activity were fabricated on a large scale by a simple spray-hydrolytic method at 90°C. The as-prepared TiO2 spherical powders were characterized by X-ray diffraction, N2 adsorption–desorption measurements, field emission scanning electron microscope, transmission electron microscopy, UV–visible diffuse reflectance spectra and photocurrent measurements. The photocatalytic activity was evaluated by photocatalytic decomposition of toluene in air. The effects of calcination temperatures on the microstructures and photocatalytic activity of the TiO2 powders were investigated and discussed. The results revealed that a large amount of mesoporous titania nanospheres could spontaneously form by self-assembly of countless tiny TiO2 primary nanoparticle during the spray hydrolysis at 90°C. The calcination temperature exhibited a strong effect on the microstructures and photocatalytic activity of the prepared titania. The 400°C-calcined sample showed the highest photocatalytic activity and was about two times higher than that of Degussa P25. At 600°C, the photocatalytic activity decreased because of the destruction of bimodal mesoporous structure of the titania and the drastic decrease of specific surface areas. [Copyright &y& Elsevier]

Abstract: Au–TiO2 nanocomposite microspheres were prepared by hydrothermal treatment of precipitates of tetrabutyl titanate (Ti(OC4H9)4) in a mixed solution of water, ethanol and Au colloid particles at 180°C for 7h. The as-prepared products were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen sorption, UV–visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and photoluminescence spectroscopy. The photocatalytic activity was evaluated by photocatalytic oxidation decomposition of formaldehyde in air. The results showed that the presence of nanosized Au particles slightly depressed the grain growth of anatase, resulting in smaller crystallite size and greater specific surface areas. Moreover, the absorbance and photoluminescence of anatase TiO2 was modified by those added Au nanoparticles and an appropriate Au amount in Au–TiO2 nanocomposite microspheres led to increase of band gap, decrease of photoluminescence intensity and prolongation of life of photo-generated electrons and holes. The photocatalytic activity of Au–TiO2 nanocomposite microspheres was obviously higher than that of pure TiO2 microspheres and Degussa P25. When the atomic percentage ratio of Au to Ti was below 0.00425, the apparent reaction rate constants increased. When the atomic percentage ratio of Au to Ti reached 0.00425, the sample displayed the highest photocatalytic activity. [Copyright &y& Elsevier]

Abstract: Hierarchically organized γ-AlOOH hollow spheres with nanoflake-like porous surface textures were fabricated by chemically induced self-transformation of metastable solid particles of amorphous aluminium oxyhydroxide produced in situ within hydrothermal reaction mixtures containing aluminium sulfate and urea. Thermal treatment of the γ-AlOOH product at 600°C produced intact hollow spheres of γ-Al2O3. Formation of the hollow γ-AlOOH structures was strongly dependent on the reaction temperature and time, as well as the concentration and molar ratio of the reactants. Hollow γ-AlOOH spheres were not obtained using mixtures of urea and aluminium nitrate or aluminium chloride, as metastable precursor particles were not produced under these conditions. In general, the described method is efficient and environmentally benign, and has significant advantages over traditional template approaches to the large-scale production of hollow inorganic materials. The prepared hierarchically organized γ-AlOOH and γ-Al2O3 hollow spheres should have important applications in areas of catalysis, separation science, biomedical engineering and nanotechnology. [Copyright &y& Elsevier]

Abstract: Peanut-shaped CaCO3 aggregates, featured of two dandelion-like heads built up from rod-like subunits, have been synthesized via a facile precipitation reaction between Na2CO3 and CaCl2 at ambient temperature in the presence of magnesium ions and ethanol solvent. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The results show that a high magnesium concentration and ethanol solvent are necessary for the formation of the unusual peanut-like aggregates. In addition, a multistep phase transformation process from amorphous calcium carbonate (ACC) to a mixture of ACC and calcite and ultimately to calcite and aragonite was observed in the formation process of the unusual structures. A possible mechanism for the formation of the unusual peanut-shape aggregates has been proposed and discussed. [Copyright &y& Elsevier]

Abstract: Tungsten trioxide hollow microspheres were prepared by immersing SrWO4 microspheres in a concentrated HNO3 solution, and then calcined at different temperatures. The prepared tungsten oxide samples were characterized by X–ray diffraction, X–ray photoelectron spectroscopy, Fourier transform infrared spectra, differential thermal analysis–thermogravimetry, UV–visible spectrophotometry, scanning electron microscopy, N2 adsorption/desorption measurements. The photocatalytic activity of the samples was evaluated by photocatalytic decolorization of rhodamine B aqueous solution under visible-light irradiation. It was found that with increasing calcination temperatures, the average crystallite size and average pore size increased, on the contrary, Brunauer–Emmett–Teller-specific surface areas decreased. However, pore volume and porosity increased firstly, and then decreased. Increasing calcination temperatures resulted in the changes of surface morphology of hollow microspheres. The un-calcined and 300°C-calcined samples showed higher photocatalytic activity than other samples. At 400°C, the photocatalytic activity decreased greatly due to the decrease of specific surface areas. At 500°C, the photocatalytic activity of the samples increased again due to the junction effect of two phases. [Copyright &y& Elsevier]

Abstract: ZnO micrometer-sized rods with tunable aspect ratios and 3D hollow spherical superstructures are selectively fabricated by a simple poly(sodium 4-styrene-sulfonate) (PSS)-mediated hydrothermal crystallization and assembly strategy. When PSS concentration is relatively low (0–0.5 g L), the aspect ratios of as-obtained microrods steadily decrease with increasing PSS concentration due to the selective adsorption of PSS on the polar ZnO (001) crystal plane. When PSS concentration is relatively high (1 g L), 3D nanosheets-built hollow microspheres form probably due to the organic–inorganic interfacial cooperative assembly. Raman, photoluminescence and UV–vis diffuse reflectance spectra show that the optical properties of as-obtained ZnO microstructures are highly related to their specific morphologies. [Copyright &y& Elsevier]

Abstract: The morphogenesis and phase changes of calcium carbonate in an ethanol/water mixed solvent in the presence of polyelectrolyte poly-(sodium 4-styrene-sulfate) (PSSS) were carefully investigated. The results showed that the ethanol volume content in the mixed solvent, temperature, the molar ratio of [CO3 2−]/[Ca2+] (R), and the concentrations of PSSS and CaCO3 turned out to be important parameters for the control of morphologies and polymorphs of CaCO3. Various morphologies of CaCO3 particles, such as rhombohedras, cubes, flowers, spheres, pancakes, etc. could be obtained dependent on the experimental conditions. Especially, monodispersed spheroid vaterite particles were obtained at the concentration of CaCO3 of 4mM. In addition, pancake-like vaterite particles were synthesized at 100°C. This research may provide a promising route for the selective synthesis of other inorganic materials with different morphologies and polymorphs. [Copyright &y& Elsevier]

Abstract: Novel dendrite-like SnS particles were synthesized for the first time by a facile solvothermal method based on the reaction between tin dichloride dihydrate (SnCl2·2H2O) and thiourea (Tu) in a mixed solvent of ethylenediamine (En) and dodecanethiol (De) at 200°C for 24h. The as-prepared products were characterized by X-ray diffraction and scanning electron microscopy (SEM). The experimental results showed that the concentration of SnCl2·2H2O and the relative volume ratios of En to De played important roles in the formation of unusual dendrite-like SnS architectures. On the basis of the experimental results, it was concluded that the formation of dendrite-like SnS particles was due to the oscillation of the concentration of Sn2+ ions at the vicinity of the growing surfaces, and the consequent periodic growth of the crystals. [Copyright &y& Elsevier]

Abstract: SnO2/TiO2 composite films were fabricated on transparent electro-conductive glass substrates (F-doped SnO2-coated glass:FTO glass) via an electrophoretic deposition (EPD) method using Degussa P25 as raw materials, and were further characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), UV–vis diffuse reflectance spectra and Photoluminescence spectra (PL). XRD and XPS results confirmed that the films were composed of TiO2 and SnO2. FESEM images indicated that the as-prepared TiO2 films had roughness surfaces, which consisted of nano-sized particles. The effects of calcination temperatures on the surface morphology, microstructures and photocatalytic activity of SnO2/TiO2 composite films were further investigated. All the prepared SnO2/TiO2 composite films exhibited high photocatalytic activities for photocatalytic decolorization of Rhodamine-B aqueous solution. At 400°C, the SnO2/TiO2 composite films showed the highest photocatalytic activity due to synergetic effects of low sodium content, good crystallization, appropriate phase composition and slower recombination rate of photogenerated charge carriers. [Copyright &y& Elsevier]

Abstract: Novel flower-like α-manganese sulfide (MnS) particles are solvothermally synthesized via a precipitation reaction of manganese dichloride (MnCl2) and thiourea (Tu) in ethylene glycol (Eg) solvent at 180°C for 24h. The as-prepared products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The influences of experimental parameters, including reaction temperatures and time, molar ratio R of MnCl2 to Tu, and solvents on the morphologies of the products were investigated. It was found that appropriate experimental conditions were crucial for the formation of unusual flower-shaped α-MnS particles. Various crystal morphologies, such as flowers, spheres, and polyhedrons could be fabricated by changing the experimental conditions. A possible formation mechanism was proposed to explain the formation of novel flower-like α-MnS particles. [Copyright &y& Elsevier]

Abstract: Crystalline bi-phase TiO2 hollow microspheres with mesoporous shells are one-pot fabricated by hydrothermal treatment of acidic (NH4)2TiF6 aqueous solution in the presence of glucose at 180°C for 24h, and then calcined at different temperatures for 4h. The as-prepared samples are characterized by XRD, SEM, TEM and nitrogen adsorption–desorption isotherms. The photocatalytic activity of the as-prepared samples is evaluated by photocatalytic decolorization of methyl orange aqueous solution at ambient temperature. The results indicate that the prepared TiO2 samples possess a bimodal pore size distribution in the mesoporous region. At 500°C, TiO2 hollow microspheres exhibit the highest photocatalytic activity probably due to an optimal mass ratio of rutile to anatase. [Copyright &y& Elsevier]

Abstract: Bi2WO6 hierarchical multilayered flower-like assemblies are fabricated on a large scale by a simple hydrothermal method in the presence of polymeric poly(sodium 4-styrenesulfonate). Such 3D Bi2WO6 assemblies are constructed from orderly arranged 2D layers, which are further composed of a large number of interconnected nanoplates with a mean side length of ca. 50nm. The bimodal mesopores associated with such hierarchical assembly exhibit peak mesopore size of ca. 4nm for the voids within a layer, and peak mesopore size of ca. 40nm corresponding to the interspaces between stacked layers, respectively. The formation process is discussed on the basis of the results of time-dependent experiments, which support a novel ‘coupled cooperative assembly and localized ripening’ formation mechanism. More interestingly, we have noticed that the collective effect related to such hierarchical assembly induces a significantly enhanced optical absorbance in the UV–visible region. This work may shed some light on the design of complex architectures and exploitation of their potential applications. [Copyright &y& Elsevier]