Visible-light driven ordered mesoporous metal ion doped anatase TiO 2 photocatalysts were synthesized via a hard-template chemical route. The effects of metal ion doping on the band energy level, surface area, pore volume, pore diameter, and photocatalytic properties of the ordered mesoporous anatase TiO 2 were systematically investigated. X-Ray photoelectron spectra and UV-vis absorption spectra indicate that the W and Mn ions enter into the lattice of anatase TiO 2 in the presence of W 6+ and Mn 3+ /Mn 4+ , resulting in a band gap transition with a red shift from the ultraviolet to the visible range, preventing the recombination rate of electron-hole pairs, therefore the photocatalytic activity can be greatly enhanced in the visible region. There exists an optimal doping level of 5 mol% W and 0.5 mol% Mn, respectively, with 95% MB and 82% MB being photocatalytically decomposed within 70 min under the visible light for 5% W and 0.5% Mn doped mesoporous anatase TiO 2 , respectively. Importantly, W ion doped TiO 2 displays much higher photocatalytic efficiency than Mn ion doped TiO 2 , which can be attributed to the presence of much higher Lewis surface acidity of W 6+ doped TiO 2 surface with a higher affinity for chemical species having unpaired electrons than Mn doped TiO 2 . In addition, the W doping induced grain refinement, highly crystalline state, large surface area and large pore size additionally contribute to the improved photocatalytic activity of the mesoporous W-doped TiO 2 samples. The enhanced ability to absorb visible light makes the ordered mesoporous metallic ion doped TiO 2 an effective photocatalyst for solar-driven applications. IntroductionBecause of its superior photocatalytic activity, chemical stability, low cost, and nontoxicity, TiO 2 has attracted much attention due to its potential applications as a photocatalyst, 1 electrode 2 and gas sensor 3 for its unique electronic and optical properties. A variety of TiO 2 nanostructured materials have been especially attracting increased attention in the realm of photocatalysis. [4][5][6][7][8] Ordered mesoporous materials, since their first discovery in 1992, 9 have found various applications such as adsorption, catalysis, energy storage and biosensors due to their high specific surface area, pore volume, and controlled pore structure. Due to their high surface areas and greatly organized pore structures, mesoporous materials can further enhance the photocatalytic activity and find potential applications in many fields. The fabrication techniques to mesoporous TiO 2 include soft template and hard template methods. The synthesis route using surfactants (P123, 10 F127, 11 etc.) as soft templates usually causes amorphous oxides because the soft template cannot tolerate the high crystallization temperature. On the other hand, mesoporous crystalline TiO 2 can be synthesized using hard templates (CMK-3, 12 SBA-15, 13 KIT-6, 14 etc.), which can resist high temperature, and the hard templates be easily removed. Therefore, the hard template method is m...
We designed a facile infiltration route to synthesize mesoporous hollow structured Mo doped SnO2 using silica spheres as templates. It is observed that Mo is uniformly incorporated into SnO2 lattice in the form of Mo(6+). The as-prepared mesoporous Mo-doped SnO2 LIBs anodes exhibit a significantly improved electrochemical performance with good cycling stability, high specific capacity and high rate capability. The mesoporous hollow Mo-doped SnO2 sample with 14 at% Mo doping content displays a specific capacity of 801 mA h g(-1) after 60 cycles at a current density of 100 mA g(-1), about 1.66 times higher than that of the pure SnO2 hollow sample. In addition, even if the current density is as high as 1600 mA g(-1) after 60 cycles, it could still retain a stable specific capacity of 530 mA h g(-1), exhibiting an extraordinary rate capability. The greatly improved electrochemical performance of the Mo-doped mesoporous hollow SnO2 sample could be attributed to the following factors. The large surface area and hollow structure can significantly enhance structural integrity by acting as mechanical buffer, effectively alleviating the volume changes generated during the lithiation/delithiation process. The incorporation of Mo into the lattice of SnO2 improves charge transfer kinetics and results in a faster Li(+) diffusion rate during the charge-discharge process.
We present a novel type of SrTiO 3 /TiO 2 nanosheet heterostructures via a facile hydrothermal process, with a tunable microstructure, phase component and surface area by adjusting the molar ratio of Sr and Ti precursors. The synthesized SrTiO 3 /TiO 2 heterostructure nanostructures can provide a high surface area and porous structure for improving dye loading capacity and hence the amount of photogenerated charges contributing to the photocurrent. The formation of heterostructures between SrTiO 3 and TiO 2 with a uniquely matched bad gap energy structure can efficiently separate photogenerated charge carriers. Photoluminescence emission and electrochemical impedance spectroscopy (EIS), incident photon-to-electron conversion efficiency (IPCE) measurements reveal a lower recombination rate of photogenerated electrons and holes, and a longer electron lifetime for the DSSCs based on the SrTiO 3 /TiO 2 heterostructures. The photoelectric conversion efficiency and short-circuit current density of DSSCs based on SrTiO 3 /TiO 2 heterostructures are greatly enhanced over that of pure TiO 2 nanosheets. DSSCs based on the SrTiO 3 /TiO 2 heterostructures shows a highest short-circuit current density of 12.55 mAcm -2 and a maximal photoelectric conversion efficiency of 7.42% under one sun illumination.13 heterostructure nanosheets, the strong uptake ability of dye molecule due to the larger surface area and porous structure characteristics, and the electron transported facilitated by the heterojunctions.
We report on solar cells based on CdS QD sensitized anatase TiO 2 hierarchical nanostructures prepared via a facile and controlled hydrothermal process. To adjust the size of CdS QDs, the TiO 2 surfaces were first treated with thiolactic acid which provides a binding site for Cd 2+ ions. CdS QDs with controllable size are grown onto the TiO 2 hierarchical nanostructures. The CdS QDs/TiO 2 hierarchical heterojunction nanocomposites display a red shift from the ultraviolet to the visible light region with a longer wavelength for the absorption edge. The matching of band edges between CdS and TiO 2 to form a semiconductor heterojunction plays an important role in effective separation of light induced electrons and holes, providing a promising photoanode for its wide absorption spectrum, high electron injection efficiency, and fast electron transference. Under UV-vis irradiation, both CdS and TiO 2 are excited. Under visible light irradiation, photons are captured by CdS QDs, with the photogenerated electron-hole pairs rapidly separated into electrons and holes at the interface between TiO 2 and CdS QDs. In addition to this, more photoelectrons are generated from TiO 2 by harvesting UV photons. TiO 2 collects the photoelectrons from CdS and passes them through to the back contact. The holes (from both CdS and TiO 2 ) generated in the process are transferred to the solid-liquid interface. Under one sun illumination, the solar cells based on CdS QDs/TiO 2 hierarchical heterojunction nanocomposites with a smaller average size of 7.6 nm for CdS QDs show a maximum short circuit current density of 6.09 mA cm −2 and a conversion efficiency of 3.06%. The performance improvement of the solar cells based on CdS QDs/TiO 2 hierarchical nanostructures can be attributed to the unique microstructure characteristics and the bandgap energy matching between the CdS QDs and TiO 2 .
We developed a facile strategy for the fabrication of uniform Au inlaid Zn2SnO4/SnO2 hollow rounded cubes with an adjustable Au loading content using ZnSn(OH)6 as the precursor, chloroauric acid as the Au source and ascorbic acid as the reducing agent.
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