Anion-Incorporation Model Proposed for Interpreting the Interfacial Physical Origin of the Faradaic Pseudocapacitance Observed on Anodized Valve Metals—with Anodized Titanium in Fluoride-Containing Perchloric Acid as an Example

Kong, Desheng

doi:10.1021/la9036869

Cited by 36 publications

(46 citation statements)

References 97 publications

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“…Only the impedance data in the active and passive regions are modeled since the transpassive region is expected to have 3D oxide and have been analyzed extensively. 10,19,20 The best fit kinetic parameters are given in Table III. The dc current vs. potential predicted from this model are shown as dashed lines in Fig. 1 and it is clear that they match reasonably well in the active and passive regions.…”

Section: H608mentioning

confidence: 99%

A Kinetic Model for the Anodic Dissolution of Ti in HF in the Active and Passive Regions

Fasmin

Praveen

Ramanathan

2015

J. Electrochem. Soc.

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We investigated the anodic dissolution of polycrystalline titanium rotating disc electrode in 0.1 M hydrofluoric acid in active and passive regions using potentiodynamic polarization and electrochemical impedance spectroscopy. In the active region, complex plane plots of the impedance spectra exhibited three capacitive loops indicting the presence of at least two adsorbed intermediates. In the passive region, they exhibited a negative resistance and a low frequency inductive loop. The high frequency loops exhibit constant phase element behavior indicating that a heterogeneous 2D film with partial surface coverage is present in the active and passive regions. The impedance data was fit to a reaction model and a four step mechanism with two adsorbed intermediate species is proposed to explain the observed trends in the active and passive regions. The change in the surface coverage of the adsorbed intermediate species, with the overpotential is estimated. This model describes the dissolution of Ti via two parallel paths, viz. a chemical step and an electrochemical step. The onset of passivation ensues when the rate of TiO 2 film formation is more than that of its dissolution. Transpassive dissolution becomes dominant when the electrochemical dissolution from the bare surface becomes negligible. Titanium metal and its alloys are widely used in engineering applications and medical implants, due to their low density, high corrosion resistance and high strength.1 These materials possess excellent corrosion resistance in acidic media, through the formation of protective oxide film on the metal surface. In order to facilitate the attack of the passive oxide layer, solutions containing fluoride ions are used for the anodic dissolution of titanium. [2][3][4] The corrosion studies of titanium show that at low overpotentials, the dissolution is in active region, and at moderate overpotentials, surface passivation occurs. At high overpotentials, transpassive dissolution is observed.The dissolution mechanism of titanium in solutions, with and without fluoride ions have been characterized using various techniques. The dissolution of Ti in 10 M H 2 SO 4 was investigated using polarization and impedance techniques 5 and it was reported that the dissolved species is Ti 3+ . To the best of our knowledge, the earliest report on electrochemical studies of Ti dissolving in acidic fluoride ions was published by Kelly.6 Polarization studies show clear active, passive and transpassive regions. 6 The impedance spectrum was acquired in the transpassive region and was analyzed to show that the film thickness increased with the potential. 6 The impedance of Ti in solutions containing strong acids (H 2 SO 4 and HNO 3 ) along with 0.1 mM -10 mM hydrofluoric acid was analyzed 4 and a four step reaction mechanism involving Ti + , Ti 2+ and Ti 3+ adsorbed intermediate species and Ti 3+ dissolved species was proposed to explain the results. In each case, the spectra were acquired at only one potential. The confidence in the model identification wo...

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Section: H608mentioning

confidence: 99%

A Kinetic Model for the Anodic Dissolution of Ti in HF in the Active and Passive Regions

Fasmin

Praveen

Ramanathan

2015

J. Electrochem. Soc.

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“…The dependence of d ox on E F is linear (Fig. 4a) as predicted by the oxide film growth model [4][5][6][7][8][9]; however, it is worth mentioning that, although this dependence remained with higher HF concentration in the solution, the slope of this straight line became increasingly greater, showing an increment in film growth ratio with a higher HF concentration in the solution (Fig. 4a).…”

Section: Electric Equivalent Circuitmentioning

confidence: 62%

“…Subsequently, inductance is observed; this is commonly related to the adsorption of negatively charged species, in this case, F − ions, at the oxide surface [9]. Eventually, at lower frequencies, a capacitive behavior appears; the physical meaning of this component keeps being a little controversial, the reason for which will be discussed further on [8][9][10]12].…”

Section: Potentiostatic Anodizationmentioning

confidence: 98%

“…2d, e, and f). Impedance plots show the presence of three time constants [5][6][7][8][9][10][11][12]: in the high-frequency region, a behavior observed is typical of the resistor-capacitor (RC) circuit, due to the resistance and capacitance of the oxide film formed at the metal surface. Subsequently, inductance is observed; this is commonly related to the adsorption of negatively charged species, in this case, F − ions, at the oxide surface [9].…”

Section: Potentiostatic Anodizationmentioning

confidence: 99%

“…Impedance plots show the presence of three time constants [5][6][7][8][9][10][11][12]: in the high-frequency region, a behavior observed is typical of the resistor-capacitor (RC) circuit, due to the resistance and capacitance of the oxide film formed at the metal surface. Subsequently, inductance is observed; this is commonly related to the adsorption of negatively charged species, in this case, F − ions, at the oxide surface [9]. Eventually, at lower frequencies, a capacitive behavior appears; the physical meaning of this component keeps being a little controversial, the reason for which will be discussed further on [8][9][10]12].…”

Section: Potentiostatic Anodizationmentioning

confidence: 99%

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Modification of growth parameters of Ti anodic films by fluoride ion insertion

Acevedo–Peña

González

2012

J Solid State Electrochem

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The potentiostatic growth of Ti anodic films formed in 0.1 M HClO 4 /xM HF (0.05 M≤x≤0.50 M) media was studied by electrochemical impedance spectroscopy, EIS. The obtained EIS spectra were analyzed by using the surface charge approach model, which showed oxide growth parameters being modified as the HF concentration increased. While the electric field through the film decreased, oxide growth rate and atomic half jump distance increased, evidencing that fluoride ions are inserted into the oxide through oxygen vacancies, thereby modifying the lattice structure and electric properties of the oxide. Additionally, the experimental data obtained for the pseudocapacitance C 0 , appearing at low-frequency domain, allowed the interpretation commonly given for this element (modulation of film thickness) to be discarded; instead, the F − ion diffusion coefficient was estimated, casting with variation of electric properties with HF concentration and E F .

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Interfacial and bulk processes during oxide growth on titanium in ethylene glycol-based electrolytes

Stancheva

Bojinov

2013

J Solid State Electrochem

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Anion-Incorporation Model Proposed for Interpreting the Interfacial Physical Origin of the Faradaic Pseudocapacitance Observed on Anodized Valve Metals—with Anodized Titanium in Fluoride-Containing Perchloric Acid as an Example

Cited by 36 publications

References 97 publications

A Kinetic Model for the Anodic Dissolution of Ti in HF in the Active and Passive Regions

A Kinetic Model for the Anodic Dissolution of Ti in HF in the Active and Passive Regions

Modification of growth parameters of Ti anodic films by fluoride ion insertion

Interfacial and bulk processes during oxide growth on titanium in ethylene glycol-based electrolytes

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