Introduction to Specific Adsorption

Дамаскин, Б. Б.; Петрий, О. А.

doi:10.1002/9783527610426.bard010301

Cited by 19 publications

(34 citation statements)

References 68 publications

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“…The two assumptions used in the modeling were as follows: 1) the ORR at the FC cathode occurs under a mixed diffusionkinetic control, i.e. kinetic current I k can be extracted from the total current I after a correction for the diffusion limiting current I d 11 :…”

Section: Numerical Modeling Of the Effect Of Chloride On The Fc Perfo...mentioning

confidence: 99%

“…Chloride ions are a negatively charged species, the adsorption of which on Pt electrodes is potentialdependent. [11][12][13][14] Bagotzky et al 12 demonstrated that the adsorption of chloride ions on the surface of a smooth polycrystalline Pt electrode in liquid electrolyte decreases as the electrode surface becomes more negatively charged. Thermodynamic 13,15 and surface X-Ray scattering (SXS) 16 studies of chloride adsorption on Pt (111) have shown the same trend, with chloride coverage decreasing with potential from 0.7 to 0.2 V vs SHE, even when accounting for the competitive adsorption of hydrogen adatoms.…”

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confidence: 99%

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The Influence of Cell Voltage on the Performance of a PEM Fuel Cell in the Presence of HCl in Air

Батурина

Epshteyn

Northrup

et al. 2014

J. Electrochem. Soc.

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The performance degradation is probed for a proton exchange membrane fuel cell (PEMFC) exposed to 4 ppm HCl in air at cell voltages of 0.4, 0.5 and 0.6 V. While the steady-state cell current decreases by 90% for the cells held at 0.6 V, it only decreases by 17% when the cells are at 0.4 V. We hypothesize that Cl − poisoning is more pronounced at 0.6 V vs. 0.4 V due to increase in Cl − coverage of the Pt nanoparticle electrocatalysts as the cell voltage (and electrode potential) becomes more positive, implying chemisorption coupled to an electrostatic effect. Chloride coverage increases by ca. 30% as cell voltage increases from 0.4 to 0.6 V. Further losses are caused by a 12% decrease in Pt electrochemical surface area (ECSA) due to Pt dissolution to chloroplatinate ions, followed by growth and agglomeration of Pt nanoparticles.The performance of proton exchange membrane fuel cells (PEMFCs) in the marine environment can be compromised by sodium chloride, a major component of sea water and air mists. 1 Chloride ions can also be introduced into the fuel cell as a by-product in the hydrogen produced from chlor-alkali plants. 2 Chloride ions inhibit the oxygen reduction reaction (ORR) at the FC cathode, affecting the ORR both in the kinetic and the diffusion regions. 3-6 Inhibition of the ORR in the kinetic region at the FC cathode is accompanied by the generation of hydrogen peroxide, which is detrimental for fuel cell performance. Increase in hydrogen peroxide generation in the presence of chloride ions at the FC cathode was recently confirmed by an increase in fluoride release rate in the FC effluent water, attributed to break down of the perfluorosulfonic acid (PFSA) membrane by peroxide radicals. 7 In addition to inhibiting the ORR and affecting its mechanism, chloride ions promote dissolution of carbon-supported Pt nanoparticles (Pt/VC), causing irreversible loss of Pt ECSA. 1,4,5,7 Previously, we explored the mechanisms of the influence of chloride ions on the FC cathode degradation, and methods for performance recovery. 3 Chloride ions were introduced into the air stream in the form of gaseous HCl premixed with air. The cell was held at a voltage of 0.6 V, and the FC cathode was exposed to 4 ppm HCl in air for 24 h. Through a combination of methods including electrochemistry, ex-situ X-Ray absorption near-edge structure (XANES) spectroscopy, and high-resolution transmission electron microscopy (HRTEM), we found that HCl poisoning results in the generation of chloride and chloroplatinate ions on the surface of Pt/VC catalysts. While chloride ions are responsible for inhibiting the ORR via adsorption and changing wetting properties of the diffusion media/catalyst layer, 6 the chloroplatinate ions promote the growth of Pt nanoparticles likely due to a Pt dissolution-redeposition mechanism. We found that chloroplatinate ions can be generated both by electrochemical and chemical mechanisms. Electrochemical Pt dissolution to PtCl 6 2− ions occurs according to Eq. 1,where E 0 and SHE stand for the standard equilibri...

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Section: Numerical Modeling Of the Effect Of Chloride On The Fc Perfo...mentioning

confidence: 99%

mentioning

confidence: 99%

The Influence of Cell Voltage on the Performance of a PEM Fuel Cell in the Presence of HCl in Air

Батурина

Epshteyn

Northrup

et al. 2014

J. Electrochem. Soc.

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“…25,28 It is known that the adsorption ability of halogen ions increases in the order Cl 2 ,Br 2 ,I 2 , which is usually explained by the decrease in hydration energy with increasing ion radius. 24,30,31 This suggests that the bromide ions will attain the critical surface concentration for pitting, X { ½ s cr , at a lower bulk electrolyte concentration by reason of its better adsorption ability relative to the chloride ion. This allows the initiation and stable growth of pits in more dilute bromide solutions, despite their lower reaction ability as compared with that of chloride ions.…”

Section: Critical Halide Ions Concentrationsmentioning

confidence: 99%

Effect of halide anions and temperature on initiation of pitting in Cr–Mn–N and Cr–Ni steels

Tzaneva¹,

Fachikov²,

Raicheff³

2006

Corrosion Engineering, Science and Technology

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9 steels in halide solutions (F 2 , Cl 2 , Br 2 and I 2 ) has been investigated. The study involved cyclic potentiodynamic polarisation tests with subsequent examination of the specimens by both optical and scanning electron microscopy. Values of the critical concentrations of halide ions, [X 2 ] cr , beyond which pitting occurs, as well as breakdown potentials for pitting in chloride solution, have been established. In addition, the effect of the temperature over the range of 5-80uC on the critical chloride ion concentration [Cl 2 ] cr has been investigated and it has been found that temperature has a negligible effect beyond 40uC.

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“…1b͒, which usually results from specific adsorption of anions. 14 We assume that for this bath in the absence of high adsorption ability organic anions specific adsorption of WO 4 2− ions takes place. Because concentration of such ions in solution is high, this adsorption causes charge exchange of the electrode surface.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Study of the Mechanism of Ag(W) Electroless Deposition

Inberg

Bogush

Croitoru

et al. 2007

J. Electrochem. Soc.

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We present an electrochemical study of the mechanism of silver-tungsten, Ag͑W͒, thin film electroless deposition from the solutions that are used for micro-systems-metallization applications. Ag͑W͒ electroless films were deposited on palladiumactivated surface of thin silicon dioxide layers on silicon substrates from ammonia-acetic or benzoate silver complex based solutions at room temperature using hydrazine hydrate as a reducing agent. These solution compositions have been investigated. The adsorption mechanism of tungsten incorporation into Ag coating on the positively charged silver surface was proposed and its co-deposition with silver due to interfacial catalytic interaction between tungsten and silver ions in form of Ag 2 W 2 O 7 was shown. The kinetics of the Ag͑W͒ electroless deposition process was analyzed by mixed potential theory. It was shown that the anodic charge-transfer reaction for ammonia-acetic solution and the diffusion of reduced silver ions to substrate for benzoate complex have controlled this process.

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Introduction to Specific Adsorption

Abstract: The sections in this article are

Cited by 19 publications

References 68 publications

The Influence of Cell Voltage on the Performance of a PEM Fuel Cell in the Presence of HCl in Air

The Influence of Cell Voltage on the Performance of a PEM Fuel Cell in the Presence of HCl in Air

Effect of halide anions and temperature on initiation of pitting in Cr–Mn–N and Cr–Ni steels

Electrochemical Study of the Mechanism of Ag(W) Electroless Deposition

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