Exfoliating KTiNbO5 particles into nanosheets

doi:10.1016/S0009-2614(03)01202-8

Chemical Physics Letters

Volume 377, Issues 3–4, 15 August 2003, Pages 445-448

https://doi.org/10.1016/S0009-2614(03)01202-8 Get rights and content

Abstract

KTiNbO₅ nanosheets have been prepared by a simple intercalation and exfoliation method. The structures of these nanosheets were analyzed, the formation mechanism was discussed and bandgap was measured to be about 3.2 eV.

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Acknowledgments

This work was supported by the Ministry of Science and Technology (Grant No. 001CB610502), National Science Foundation of China (Grant No. 90206021), Chinese Academy of Sciences and Peking University.

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Base-free selective oxidation of benzyl alcohol in water over palladium catalyst supported on titanium niobate nano sheets
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Recently several novel metal NPs have been successfully immobilized on the surface of niobates/titanates nanosheets and organized into novel materials with fascinating functional properties [3,35–37]. Potassium titanoniobate (KTiNbO5) is a typical layered Ti-Nb oxide in which the alkali ions lie between layers built up from zigzag chains of edge-sharing MO6 octahedra [38]. To the best of our knowledge, there have been no previous reports about the utilization of titanoniobate nano sheets as the support for Pd NPs.
Exploring catalysts with high-efficiency, stability and mild reaction conditions for oxidation of alcohols is an urgent task. In this work, a simple and efficient nanostructured catalyst system is developed, comprising homogenously dispersed Pd nanoparticles (NPs) with the average sized of 2.84 nm supported on titanoniobate nano sheets.
The metal precursors are deposited onto the exfoliated TiNbO₅ nano sheets through the electrostatic interaction and then reduced to nanoparticles by the UV irradiation. Selective oxidation of benzyl alcohol in ultrapure water was achieved with the as-prepared Pd-TNO under conditions of the base-free and atmospheric pressure with using air as an oxidant.
The results demonstrate that the catalyst exhibits excellent catalytic activity and selectivity in the aerobic oxidation of benzyl alcohol to benzaldehyde. Furthermore, the catalyst can be reused to five times without significant loss of performance. The nanostructure obtained with the exfoliation/restacking process favors the mass transfer and provides a unique nano reactor during the reaction.
2D titanoniobate-titaniumcarbide nanohybrid anodes for ultrafast lithium-ion batteries
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Previous studies on low-dimensional nanostructures, such as ultrathin 2D nanosheets with large specific surface area, have demonstrated this to be an effective strategy to improve lithium storage performance dominated by pseudocapacitive effects due to the enhanced exposure of near-surface redox sites and shortening the pathway of Li ions diffusion [26]. In particular, ultrathin HTiNbO5 nanosheets could be facilely synthesized through the exfoliation of bulk HTiNbO5 and subsequent acid-induced flocculation of the [TiNbO5]- monolayers [27]. The electrochemical performance of such HTiNbO5 nanosheets has not been explored yet as high-rate anode material for lithium-ion batteries.
Mixed titanium-niobium oxides are considered to be promising anode candidates due to the high theoretical capacity based on the presence of multiple redox couples (Nb⁵⁺/Nb⁴⁺, Nb⁴⁺/Nb³⁺ and Ti⁴⁺/Ti³⁺). Among them, layered titanoniobates with a two-dimensional (2D) nanosheet structure are expected to expose most surface and near-surface active sites and a minimal Li⁺ diffusion pathway, and thus could exhibit ultrafast pseudocapacitive dominated lithium storage performance. This work presents the synthesis of 2D HTiNbO₅/H-Ti₃C₂T_x nanohybrid anodes via a combined exfoliation and co-flocculation strategy taking advantage of the ultrathin 2D structure of HTiNbO₅ nanosheets and the high electronic conductivity of H-Ti₃C₂T_x nanosheets. This leads to the random restacking of these two nanosheets and the formation of plane-to-plane contact, insuring excellent transfer kinetics of electrons as well as Li⁺ ions. Benefitting from such unique 2D lamellar structure, the HTiNbO₅/H-Ti₃C₂T_x nanohybrid anode with an optimized (3:1) mass ratio is able to exhibit fast lithium storage process by delivering a high capacity of 111.5 mAh•g⁻¹ at a current density of 5 A g⁻¹ (∼20.6C). Our results demonstrate the feasibility of such co-flocculation strategy for designing new high-rate anode material, which outperforms the original bulk HTiNbO₅ compound, making it a promising candidate for application in ultrafast lithium-ion batteries.
Ti<inf>2</inf>Nb<inf>2</inf>O<inf>9</inf>/graphene hybrid anode with superior rate capability for high-energy-density sodium-ion capacitors
2021, Journal of Alloys and Compounds
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HTiNbO5 nanosheets were prepared via an ion-exchange and followed by exfoliating process using layered bulk KTiNbO5 as precursor. Typically, KTiNbO5 powder was firstly prepared by calcining a stoichiometric mixture of K2CO3, TiO2 and Nb2O5 at 1100 °C for 12 h in air [27]. Then, 1 g of KTiNbO5 powder was added into 6 M HCl aqueous solution (200 mL) and stirred for three days at room temperature, the K+ ions in the interlayer were exchanged with H+ ions, the H+-intercalated HTiNbO5 was obtained.
Ti₂Nb₂O₉/reduced graphene oxide (Ti₂Nb₂O₉/RGO) hybrid anode is fabricated by flocculation of HTiNbO₅ nanosheets and graphene oxide (GO) nanosheets, followed by annealing HTiNbO₅/GO composite at 500 °C in Ar for 1 h, in which HTiNbO₅ nanosheets are prepared by ion-exchange and followed by exfoliating process using KTiNbO₅ as precursor. HTiNbO₅ nanosheets are topotactically transformed into Ti₂Nb₂O₉ nanosheets and GO is reduced into RGO by calcining the HTiNbO₅/GO composite, causing enhanced Na⁺-intercalation pseudocapacitive behavior and significantly improved conductivity for Ti₂Nb₂O₉/RGO hybrid anode. Ti₂Nb₂O₉/RGO hybrid anode delivers superior rate capability (206 mAh g⁻¹ at 4 A g⁻¹) and excellent cycling performance with 95% capacity retention at 1 A g⁻¹ over 1000 cycles. A hybrid device is assembled using Ti₂Nb₂O₉/RGO as the anode and activated carbon (AC) as the cathode, it shows a maximum high energy density of 96 Wh kg⁻¹ at a power density of 75 W kg⁻¹, and the energy density still maintains 39 Wh kg⁻¹ when the power density achieves as high as 10029 W kg⁻¹. Moreover, the assembled device displays good cycling stability with a capacity retention of 79% after 10,000 cycles. This work can provide new insights on fabrication of Ti-Nb oxides-graphene based composite anode for sodium ion capacitors.
Dielectric properties of single crystal Sr<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf> dielectric nanosheet thin films by electrophoretic deposition (EPD) and post deposition treatments
2017, Journal of Alloys and Compounds
Citation Excerpt :
Moreover, use of BT is restricted in micro-devices due to several problems, such as the rapid reduction in dielectric constant by dielectric thickness shrinkage [7], and difficulty in synthesizing nanoparticles having a grain size of 100 nm or less. A variety of materials having nanosheet structure such as Ca2Nb3O10, TiNbO5, and TiO2 [8–10] has been investigated in order to reduce the thickness of the dielectrics. It is noticeable that nanosheets have the thickness <2 nm typically and has higher dielectric constant regardless of its thin thickness [11].
Sr₂Nb₃O₁₀ (SNO) nanosheets were obtained by exfoliating from a perovskite layered structure of HSr₂Nb₃O₁₀ (HSNO). The nanosheets were deposited on substrates simultaneously with unintended tetrabutylammonium cations (TBA⁺) by electrophoretic deposition (EPD) process. To eliminate TBA⁺ from the SNO dielectric nanosheet thin films, the films were exposed to ultraviolet (UV). Since UV exposure can't decompose TBA⁺ completely, thermal annealing was additionally conducted by employing different furnaces at various atmospheres. XRD shows the reduction in lattice constant after UV and thermal treatments, indicating that TBA cations were decomposed in the interlayer of nanosheets. FT-IR spectra analysis depicted that the organic materials were eliminated through the post deposition treatments. In addition, XPS data indicated that films treated by a combination of UV and thermal had a lower relative atomic ratio of carbon and nitrogen than as-deposited and only-UV treated films. The optimum process conditions for improving dielectric properties were UV exposure for 15 h and subsequent thermal annealing in a box furnace in the air at 600 °C for 1 h. When compared to the as-deposited film, the dielectric constants of films further annealed by the box furnace in the air were increased from 8 to 27 at 1 MHz whereas dielectric loss (tan δ) decreased from 5% to 2%. Additional thermal treatment strongly affects nanosheets to decompose TBA⁺.
The hindering function of phosphate on the grain growth behavior of nanosized zirconia powders calcined at high temperatures
2011, Ceramics International
Citation Excerpt :
Therefore, the dispersion and thermal stability of nanosized ZrO2 particles play a key role in controlling the shape forming behavior and optimizing the performance of the ceramic materials. In order to achieve full densification, excessive grain growth has to be inhibited either by the incorporation of the second phase particle or solid solution alloy during sintering and high-temperature deformation [6–9]. The high temperature strongly affects the crystal structure, particle size and surface area [10].
Nanosized zirconia was prepared by a hydrothermal method using ZrOCl₂·8H₂O and NaOH as raw materials. The obtained ZrO₂ powders were soaked in the phosphate solution with different concentrations. The as-prepared ZrO₂ powders and the powders treated with phosphate solution were calcined at different temperatures from 600 to 1000 °C. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray photoelectronic spectroscopy (XPS). The experimental results show that the untreated nanosized ZrO₂ grow and agglomerate to bulk when the ZrO₂ powders were calcined at high temperatures, while the ZrO₂ powders treated with phosphate solution grow slowly and remain nanosized crystal at the same calcination temperature. This phenomenon implied that phosphate treatment played an important role in inhibiting the crystal grain growth of ZrO₂. The possible inhibition mechanism could be explained to that P species on the surface of ZrO₂ can reduce the grain boundary mobility and prevent direct contact of ZrO₂ particles.
Photocatalytic water splitting for hydrogen production on Au/KTiNbO <inf>5</inf>
2010, International Journal of Hydrogen Energy
Citation Excerpt :
In this study, we present a series of novel Au/KTiNbO5 catalysts prepared by the processes of deposition-precipitation (DP), conventional impregnation (IMP) and photodeposition from HAuCl4 for photocatalytic water splitting. The lamellar titanate niobate, KTiNbO5, has been employed for the study of photocatalytic properties due to its ion-exchangeable layered structure and photocatalytic properties [22,23]. The influence of the of HAuCl4 aqueous solution synthesis pH value on the morphology of gold cocatalysts, as well as the photocatalytic activity for the water splitting reaction, was investigated.
Gold nanoparticles were deposited on potassium titanoniobate, KTiNbO₅ using deposition-precipitation (DP), conventional impregnation (IMP) and photodeposition method in order to improve photocatalytic hydrogen production from water splitting. The effect of synthesis pH value of a HAuCl₄ aqueous solution used in the DP process on the morphology of gold nanoparticles, optical property and photocatalytic activity of water splitting under UV light irradiation was investigated. These catalysts were characterized by powder X-ray diffraction patterns (XRD), inductively coupled plasma mass spectrometry (ICP-MS), UV–visible spectroscopy (UV–vis), and Transmission Electron Microscopy (TEM). The Au/KTiNbO₅ catalysts prepared by the DP method consisted of a good metal–semiconductor interface which allowed for a much higher efficient electron-hole separation. The 0.63 wt% Au/KTiNbO₅ catalyst prepared by the DP method at pH = 10 showed a uniform dispersion of gold nanoparticles with an average gold particle size of 4.2 nm and exhibited an ultra-high photocatalytic water splitting activity (3522 μmol g⁻¹ h⁻¹), about 47 times higher than that exhibited by the KTiNbO₅ photocatalyst.

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Exfoliating KTiNbO5 particles into nanosheets

Abstract

Section snippets

Acknowledgments

J. Solid State Chem.

Science

Science

Appl. Phys. Lett.

J. Chem. Soc. Chem. Commun.

J. Phys. Chem.

J. Am. Chem. Soc.

Exfoliating KTiNbO₅ particles into nanosheets