Surface Potential at the Gas–Nonaqueous Solution Interface

Parfenyuk, V. I.

doi:10.1023/b:coll.0000037454.39079.99

Cited by 18 publications

(41 citation statements)

References 33 publications

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“…2 To the extent that this quantity has been indirectly measured at the air-water interface, early reported values strongly varied in magnitude and sign. 13 Several post-1970 experimental values are in better agreement with each other, 12,14 yielding +0.025 to 0.16 volt values (see Ref. 16, Table 1).…”

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confidence: 69%

Surface Potential at the Air−Water Interface Computed Using Density Functional Theory

Leung

2009

J. Phys. Chem. Lett.

121

145

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An accurate prediction of the surface potential (φ) at the air-water interface is critical to calculating ion hydration free energies and electrochemical half-cell potentials. Using Density Functional Theory (DFT), model interfacial configurations, and a theoretical definition of φ, we report a value of +3.63 volt at 0.92 g/cc water density. A maximally localized Wannier function analysis confirms that φ is dominated by molecular quadrupole (or "spherical second moment") contributions. We find that the predicted surface potential depends on computational details, and conclude that standard DFT codes and the existing definition of φ may not yield surface potentials directly comparable to existing experiments."Surface potentials" (or "potentials of the phase") are invoked when a charged particle moves from one phase to another through their mutual interface. One of the simplest and most important examples pertains to the surface between air and water.1-16 ("Air," "vacuum," and "vapor" will be used interchangeably in this work.) The electrostatic potential difference (φ) between an ion in vacuum at infinity and that ion in pure liquid water contributes a term qφ to the absolute hydration free energy (∆G hyd ), where q is the ionic charge. φ thus contributes to all aqueous media electrochemical half-cell potentials, 17,18 which consist of ∆G hyd plus the pertinent ionization potentials. Recent Density Functional Theory (DFT) calculations have yielded φ estimates for the air-water interface 19-23 substantially larger in magnitude than classical force field predictions 5-9 and experimental values, [12][13][14][15][16] suggesting that the methodology and physical basis of such calculations should be re-examined.We first focus on molecular simulation perspectives, [5][6][7][8][9] deferring the question of what is measured in experiments to the concluding discussions. For this purpose, we consider a charge-neutral slab of salt-free liquid water. Using this kind of simulation cell, force field-based simulations (i.e., those not based on electronic structure calculations) have reported that φ depends on the water model used, [8][9][10] but that the widely applied SPC/E model 24 yields φ=-0.55 volt, 8 similar to related threepoint point-charge water models, including polarizable ones. 9DFT takes into account electronic structure and molecular polarizabilites, and might be considered an improvement over non-polarizable water models. As will be shown, however, care must be exercised when interpreting the results based on the existing theoretical definition of the surface potential (see below).5-9 A DFT work that extrapolates the highest occupied molecular orbital in gas phase ion/water-clusters to infinite cluster size has estimated that φ ∼ 4 volt 19 (in our notation). Using the VASP code, 25 the Perdew-Burke-Ernzerhof (PBE) functional, 26 a bulk liquid simulation cell, and approximations for surface dipoles, we have deduced that φ = +4.05 volt.21 By considering pK a and proton hydration free energies in DFT simulations, Che...

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confidence: 69%

Surface Potential at the Air−Water Interface Computed Using Density Functional Theory

Leung

2009

J. Phys. Chem. Lett.

121

145

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“…A positive value of droplet surface potential (+0.1 V) indicates that the water dipoles are preferentially oriented with the negative pole toward the gas phase, while the positive pole is oriented towards the liquid phase (Parfenyuk, 2002). Botti et al (2004) suggested that OH − ions are hydrated with 4 H 2 O molecules with a presence of a weakly bound fifth water molecule, close to the hydrogen atoms.…”

Section: Air Ions In the Environmentmentioning

confidence: 99%

Characterization of ions at Alpine waterfalls

et al. 2012

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Abstract. During a three-year field campaign of measuring waterfall generated ions, we monitored five different waterfalls in the Austrian Alps. Most measurements were performed at the Krimml waterfall (Salzburg, Austria), which is the biggest waterfall in Europe, and the Gartl waterfall (Mölltal, Austria). We characterized spatial, time and size distributions of waterfall-generated ions under the influence of surrounding topography. The smallest ions with boundary diameters of 0.9, 1.5 and 2 nm, were measured with a cylindrical air ion detector (CDI-06), while ion sizes from 5.5 to 350 nm were measured using a modified Grimm SMPS aerosol spectrometer. High negative ion concentration gradients are detected in the vicinity of the waterfalls, whereas the increase of positive ions was only moderate. Ions in the nano range were the most abundant at 2 nm, and at 120 nm in the sub-micrometer range.

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“…The contact potential difference method [11] enabled us to show that, within the aforementioned concentration range, the sign of the surface potential at the solution-gas interface changes, which reflects the structure peculiarities of the solution, including that part of it close to the electrode.…”

Section: Resultsmentioning

confidence: 99%

The effect of hydrodynamic conditions on the rate of copper cathodic reduction from aqueous ethanol environments

Носков

Chulovskaya

Balmasov

et al. 2012

Prot Met Phys Chem Surf

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The effect of hydrodynamic conditions on copper electroplating from aqueous ethanol CuSO 4 solutions is studied. Adding ethanol is found to result in a decrease in the ionic mass transfer rate in the solu tion. Experimental data are analyzed on the basis of the convective diffusion equation for a rotating disc elec trode. Diffusivities of copper cations and kinetic current densities are estimated.

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Surface Potential at the Gas–Nonaqueous Solution Interface

Cited by 18 publications

References 33 publications

Surface Potential at the Air−Water Interface Computed Using Density Functional Theory

Surface Potential at the Air−Water Interface Computed Using Density Functional Theory

Characterization of ions at Alpine waterfalls

The effect of hydrodynamic conditions on the rate of copper cathodic reduction from aqueous ethanol environments

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