共查询到20条相似文献,搜索用时 15 毫秒
1.
《Electrochemistry communications》2001,3(8):395-399
The preparation and electrochemistry of dispersed Pt metal on nanoporous titanium dioxide coatings is described. It is shown that photocatalytic deposition of Pt centres on a nanoporous titanium dioxide layer fabricated from TiO2 nanoparticles leads to high surface area electrocatalysts. The reactions investigated are the evolution of hydrogen and the oxidation of carbon monoxide and methanol. 相似文献
2.
Milena Jankulovska Teresa Lana-Villarreal Roberto Gómez 《Electrochemistry communications》2010,12(10):1356-1359
Titanium dioxide nanotube electrodes were fabricated by anodization of titanium and decorated with quantum-sized rutile nanowires (2 nm in diameter) by chemical bath deposition. The length of the nanotubes (120 nm in external diameter) was varied between 4 and 10 μm by changing the anodization time. The hierarchically organized electrodes present good mechanical properties and an enhanced capacity for reversible charge accumulation. The photoelectrocatalytic properties of such electrodes have been tested by photo-oxidizing both water and oxalic acid, turning out to be superior to those of bare nanotubes, which are ascribed to an enhanced interfacial area while keeping the favorable transport properties (for both electrons and chemicals) typical of nanotube electrodes. 相似文献
3.
Lithium insertion into titanium dioxide (anatase) electrodes: microstructure and electrolyte effects
Dina Fattakhova Ladislav Kavan Petr Krtil 《Journal of Solid State Electrochemistry》2001,5(3):196-204
Insertion characteristics of anatase electrodes were studied on single-crystal and polycrystalline electrodes of different
microstructures. The lithium incorporation from propylene carbonate solution containing LiClO4 and Li(CF3SO2)2N was studied by means of cyclic voltammetry (CV), the quartz crystal microbalance (QCM) and the galvanostatic intermittent
titration technique (GITT). The electrode microstructure affects both the accessible coefficient x and the reversibility of the process. The highest insertion activity was observed for electrodes composed of crystals with
characteristic dimensions of ∼10–8 m. The insertion properties deteriorate for higher as well as for smaller crystal sizes. Enhanced insertion was observed in
Li(CF3SO2)2N-containing solutions. Lithium insertion is satisfactorily reversible for mesoscopic electrodes; the reversibility in the
case of compact polycrystalline and single-crystal electrodes is poor. The reversibility of the insertion improves with increasing
electrolyte concentration. The lithium diffusion coefficient decreases with increasing x and ranges between 10–15 and 10–18 cm2 s–1.
Electronic Publication 相似文献
4.
Monllor-Satoca D Lana-Villarreal T Gómez R 《Langmuir : the ACS journal of surfaces and colloids》2011,27(24):15312-15321
Titanium dioxide is a widely used photocatalyst whose properties can be modified by fluoride adsorption. This work is focused on the effect of surface fluorination on the electrochemical and photoelectrocatalytic properties of TiO(2) nanoporous thin films. Surface fluorination was achieved by simple addition of HF to the working solution (pH 3.5). Open circuit potential as well as ex situ XPS measurements verify that surface modification takes place. Fluorination triggers a significant capacitance increase in the accumulation potential region, as revealed by dark voltammetric measurements for all the TiO(2) samples studied. The photoelectrocatalytic properties (measured as photocurrents under white light illumination) depend on the substrate being oxidized and, in some cases, on the nature of the TiO(2) sample. In particular, the results obtained for electrodes prepared with a mixed phase (rutile + anatase) commercial nanopowder (PI-KEM) indicate that the processes mediated by surface trapped holes, such as the photooxidation of water or methanol, are accelerated while those occurring by direct hole capture from the adsorbed state (formic acid) are retarded. The photooxidation of catechol and phenol is also enhanced upon fluorination. In such a case, the effect can be rationalized on the basis of a diminished recombination and a surface displacement of both the oxidizable organic substrates and the poisoning species formed as a result of the organics oxidation. Photoelectrochemical and in situ infrared spectroscopic measurements support these ideas. In a more general vein, the results pave the way toward a better understanding of the photocatalysis phenomena, unravelling the importance of the reactant adsorption processes. 相似文献
5.
C.R. Leidner P. Denisevich K.W. Willman Royce W. Murray 《Journal of Electroanalytical Chemistry》1984,164(1):63-78
The cyclic voltammetric peaks for charging trapping and untrapping reactions between the inner and outer redox polymer films of five bilayer electrodes are compared to a theory for control of the rate of charge trapping by electron diffusion rates in the inner polymer film. The five bilayer electrodes use various different redox polymer films (electropolymerized poly-pyridine complexes of Fe, Ru, and Os, and polyvinylferrocene) arranged in different orders. The currents on the rising edge of the bilayer trapping and untrapping peaks follow the electron diffusion theory up to ca. 80% of the peak current; currents thereafter are controlled by another process(es). The analysis yields values for the electron diffusion constants in the inner bilayer polymer films, which agree with one another for different bilayers having the same inner film polymer films and which also agree with independent determinations by other methods. Two of the bilayers are made from the same two polymers, arranged in different inner-outer order. These bilayers also illustrate the occurrence of a “leak reaction”, in which charge trapped in the outer film is discharged via a thermodynamically unfavorable electron transfer reaction with the inner polymer film. 相似文献
6.
An investigation into the redox behaviour of 4‐ferrocenylcatechol bound to nanocrystalline TiO2 electrodes identified a limitation to the use of catechol as an electron‐transfer facilitating anchoring group. 4‐Ferrocenylcatechol was adsorbed to transparent nanocrystalline TiO2 electrodes. UV–visible spectra of the modified electrode were recorded in an acetonitrile‐electrolyte solution. At an applied potential of + 0.45 mV (vs Ag/AgCl/Cl?) the ferrocenyl group oxidized to the ferrocenium cation and the catecholate group oxidized to the benzoquinone form. Subsequent application of a potential of 0 V reduced the ferrocenium to ferrocene but, owing to the irreversibility of the catechol oxidation in aprotic solvents, benzoquinone is not reduced to catecholate and subsequently desorbs and is lost due into solution. Electrochromic switching of the ferrocenyl electrochromophore on TiO2 with aprotic electrolyte is, therefore, irreversible. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
7.
Silicon-doped metal oxide nanotubes are formed in Si-doped titanium dioxide prepared by a sol-gel technique. 相似文献
8.
Marta Zwolińska Kamil Załęgowski Agata Roguska Halina Garbacz Krzysztof J. Kurzydłowski 《Journal of Solid State Electrochemistry》2014,18(11):3091-3097
TiO2 nanotubes are extensively investigated because of their unique properties and wide range of applications, e.g., in biomedicine. They are used as coatings on titanium implant materials accelerating osteoblast (bone cell) adhesion and improving osteointegration. Owing to its high mechanical properties, nanocrystalline titanium is likely to replace the widely used titanium alloys, which contains harmful ions such as V and Al. The performance properties of nanocrystalline titanium can be modified by subjecting it to various surface treatments tailored to the demands of a given application. The aim of this study is to determine whether the grain refinement of the titanium substrate has an influence on the formation of TiO2 nanotubes. The TiO2 nanotubes were fabricated by anodic polarization of micro- and nanotitanium at a constant voltage of 10, 15, and 20 V for 2 h in an electrolyte containing fluoride ions. The nanocrystalline bulk titanium (grade 2) with grain size of about 90 nm and high density of dislocations was obtained using hydrostatic extrusion. Commercially available coarse-grained titanium with grain size of 20 μm was used as a reference sample. The microstructure of the fabricated nanotubular layers was revealed using scanning electron microscopy and focus ion beam microscopy. Auger electron spectroscopy and X-ray photoelectron spectroscopy were used to determine the chemical composition of the fabricated layers. The results indicate that grain refinement influences the morphology of TiO2 nanotubes while their chemistry remains unchanged. 相似文献
9.
The application of ion-selective electrodes (ISE) with ionophore-based membranes under galvanostatic polarization conditions
is briefly reviewed. The possibilities offered by polarization for expanding the working range of ISE and for varying their
selectivity and the type of electrode response (cationic or anionic) are discussed. 相似文献
10.
O. V. Popova E. A. Mar’eva D. I. Chernobrovkina 《Russian Journal of Applied Chemistry》2013,86(11):1719-1722
Possibility of forming titanium nitride by anodic polarization of the surface of titanium in water-containing organic electrolytes in the presence of NH4F at potentials of 2–14 V was demonstrated and substantiated. The method of cyclic voltammetry was used to study electrochemical processes in electrolytes based on ethylene glycol and glycerol. Results obtained in an analysis of the structural, chemical, and physicomechanical properties of the titanium nitride layers obtained in the study are presented. 相似文献
11.
Niobium diffusion in niobium-doped titanium dioxide 总被引:1,自引:0,他引:1
L. R. Sheppard A. J. Atanacio T. Bak J. Nowotny M. K. Nowotny K. E. Prince 《Journal of Solid State Electrochemistry》2009,13(7):1115-1121
The present work studied the self-diffusion coefficient of 93Nb in Nb-doped TiO2 single crystal (4.3 at.% Nb) at high oxygen activity [p(O2) = 21 kPa] over the temperature range 1,073 to 1,573 K. The diffusion-induced 93Nb concentration profile was determined by using secondary ion mass spectrometry (SIMS). The subsequently determined self-diffusion
coefficient of 93Nb exhibits the following temperature dependence:. This study builds upon a similar study performed previously for 93Nb tracer diffusion in undoped TiO2, and identifies the effect of compositional change on self-diffusion behaviour. The obtained activation energy has been considered
in terms of migration and formation enthalpies of titanium vacancies.
The present work is dedicated to Professor John Bockris on the occasion of his 85th birthday. His contribution to the progress
of modern electrochemistry is well-known to several generations of students and researchers who have been using his textbooks.
His specific contribution to the theory of photoelectrochemical water splitting is known to all working in this fascinating
area. 相似文献
12.
Xiang Chen 《International journal of quantum chemistry》2013,113(20):2295-2305
We construct a hydrogen‐bond based metal–molecule–metal junction, which contains two identical “reader” molecules, one single DNA base as a bridged molecule, and two titanium nitride electrodes. Hydrogen bonds are formed between “reader” molecules and DNA base, whereas titanium–sulfur bonds are formed between “reader” molecules and titanium nitride electrodes. We perform electronic structure calculations for both the bare bridged molecule and the full metal–molecule–metal system. The projected density of states shows that when the molecule is connected to the titanium nitride electrode, the energy levels of the bridged molecule are shifted, with an indirect effect on the hydrogen bonds. This is similar to the case for a gold electrode but with a more pronounced effect. We also calculate the current–voltage characteristics for the molecular junctions containing each DNA base. Results show that titanium nitride as an electrode can generate distinct conductance for each DNA base, providing an alternative electrode for DNA sequencing. © 2013 Wiley Periodicals, Inc. 相似文献
13.
Zhuang X Le A Steimle TC Nagarajan R Gupta V Maier JP 《Physical chemistry chemical physics : PCCP》2010,12(45):15018-15028
The electronic spectrum in the region 17?500 cm(-1) to 18?850 cm(-1) of a cold molecular beam of TiO(2) has been investigated using laser induced fluorescence (LIF) and mass-resolved resonance enhanced multi-photoionization (REMPI) spectroscopy. Bands at 18?412 cm(-1), 18?470 cm(-1) and 18?655 cm(-1) were recorded at a resolution of 35 MHz, rotationally analyzed, and assigned as the ?(1)B(2) (0,1,2) ←X[combining tilde](1)A(1) (0,0,0), ?(1)B(2) (1,0,0) ←X[combining tilde](1)A(1) (0,0,0) and ?(1)B(2) (1,1,0) ←X[combining tilde](1)A(1) (0,0,0) transitions. The dispersed fluorescence from the ?(1)B(2) (0,1,2) and ?(1)B(2) (1,0,0) levels were combined with previous results to produce an improved set of vibrational parameters for the X[combining tilde](1)A(1) state. The optical Stark effect in the ?(1)B(2) (0,1,2) ←X[combining tilde](1)A(1) (0,0,0) and ?(1)B(2) (1,0,0) ←X[combining tilde](1)A(1) (0,0,0) bands were recorded and combined with earlier results for ?(1)B(2) (1,1,0) ←X[combining tilde](1)A(1) (0,0,0) to determine the permanent electric dipole moment for these states. The origin and harmonic vibrational constants for the ?(1)B(2) state are determined to be: T(000) = 17?593(5) cm(-1), ω(1) = 876(3) cm(-1), ω(2) = 184(1) cm(-1), and ω(3) = 316(2) cm(-1). A normal coordinate analysis was performed and Franck-Condon factors calculated. 相似文献
14.
《Progress in Solid State Chemistry》2004,32(1-2):33-177
15.
First-order Raman spectra have been recorded at room temperature for the anatase and rutile phases of polycrystalline titanium dioxide using an argon ion laser as exciter. The high-temperature rutile phase was found to be stabilized at temperatures below 450°C. Anatase transforms to rutile phase at ~750°C. All the Raman active fundamentals predicted by group theory are observed. 相似文献
16.
The present work derived defect disorder diagram representing the effect of oxygen activity on the concentration of both ionic and electronic defects for undoped TiO2. This diagram was determined using the equilibrium constants derived in the present work, including (i) the intrinsic electronic equilibrium constant, (ii) the equilibrium constant for the formation of oxygen vacancies, and (iii) equilibrium constant for the formation of titanium vacancies. These equilibrium constants are consistent with three properties determined independently, including: electrical conductivity, thermoelectric power and change of mass determined by thermogravimetry. The derived defect disorder diagram may be used for tailoring semiconducting properties of TiO2 that are desired for specific applications through the selection of optimized processing conditions. 相似文献
17.
Umberto Casellato Nicola Comisso Giovanni Davolio Giuliano Mengoli 《Journal of Solid State Electrochemistry》2002,6(5):331-340
Charge storage in 40/60 TiFe alloy has been investigated using electrode fabrication powder material, either of true alloy
or of alloy precursor grades. The true alloy activated very reluctantly in that its maximum charge (i.e., hydrogen) capacity
remained below 100 mA h g–
1. In contrast, the alloy precursor could be activated to an intrinsic capacity of ~300 mA h g–1. Charge storage of the 40/60 TiFe alloy precursor was certainly affected by the redox reactions of surface Fe, but a large
amount was stored as hydrogen absorbed by the material, as indicated by a dialometric test and the poison effect. X-ray and
EDAX analyses of the two materials can account for their differing abilities to store charge.
Electronic Publication 相似文献
18.
19.
Nakaruk A. Lin C. Y. W. Channei D. Koshy P. Sorrell C. C. 《Journal of Sol-Gel Science and Technology》2012,61(1):175-178
Thin films of TiO2 doped with Fe and Mn were deposited on F-doped SnO2-coated glass by spin coating. Dopant concentrations of 3–7 wt% (metal basis) were used. The structural, chemical, and optical
characteristics of the films were investigated. Laser Raman microspectroscopy and glancing angle X-ray diffraction data showed
that the films consisted of the anatase polymorph of TiO2. X-ray photoelectron spectroscopy data indicated the presence of Fe3+, Mn4+, and Mn3+ in the doped films, as predicted by calculated thermodynamic stability diagrams, and the occurrence of atomic disorder and
associated structural distortion. Ultraviolet–visible spectrophotometry data showed that the optical indirect band gap of
the films decreased significantly with increasing dopant levels, from 3.36 eV (undoped) to 2.95 eV (7 wt% Fe) and 2.90 eV
(7 wt% Mn). These improvements are attributed to single (Fe) or multiple (Mn) shallow electron/hole trapping sites associated
with the dopant ions. 相似文献