EFFECT OF CHLORIDE ON THE KINETICS OF ELECTROÖXIDATION OF CHROMIUM(II) IN ACIDIC PERCHLORATE MEDIUM<sup>1</sup>

Aikens, D. A.; Ross, John W.

doi:10.1021/j100825a028

Cited by 40 publications

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“…When this complex is observed, the reaction has a lower apparent activation barrier, a higher exchange current density, and a change in the total number of electrons involved, implying a change in mechanism, which we attribute to the involvement of the chloride species in the reaction. Previous kinetic studies of other redox couples like Cr 2+ /Cr 3+ , 51,52 Fe 2+ /Fe 3+ , 53 and Cu 2+ / Cu + in the presence of chloride 54 showed enhanced kinetics in comparison with noninteracting HClO 4 , which were attributed to *Cl acting as a bridge instead of *OH. The faster electron transfer kinetics of the *Cl compared to the *OH were predicted to be due to better electronic coupling based on ab initio molecular orbital theory calculations.…”

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V²⁺/V³⁺ Redox Kinetics on Glassy Carbon in Acidic Electrolytes for Vanadium Redox Flow Batteries

et al. 2019

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Vanadium redox flow batteries are a promising technology for energy storage, yet the mechanism of the kinetically limiting V 2+ /V 3+ redox reaction remains poorly understood. Here, we elucidate the impact of anion complexation on V 2+ /V 3+ kinetics on a glassy carbon electrode in three common electrolytes: hydrochloric acid, sulfuric acid, and mixed HCl/H 2 SO 4 . The V 2+ /V 3+ kinetics are ∼2.5 times faster in HCl and have lower apparent activation energies than those in H 2 SO 4 or HCl/H 2 SO 4 . We also identify the presence of [V(H 2 O) 4 Cl 2 ] + species in HCl by UV−vis spectroscopy. We confirm that the V 2+ /V 3+ reaction proceeds via an adsorbed intermediate and propose a bridging mechanism through adsorbed *Cl (in HCl) and *OH (in H 2 SO 4 or HCl/H 2 SO 4 ). A bridging mechanism through *Cl is supported by even faster redox kinetics in HBr than in HCl, possibly due to the higher polarizability of *Br. By measuring the exchange current densities using steady-state current measurements and impedance spectroscopy, we show that the overall reaction is a two-electron process in HCl as opposed to a one-electron process in H 2 SO 4 and HCl/H 2 SO 4 .

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V²⁺/V³⁺ Redox Kinetics on Glassy Carbon in Acidic Electrolytes for Vanadium Redox Flow Batteries

et al. 2019

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“…Taking the isotropic rotating sphere as a valid approximation for the motion of 5'-AMP in water, rc is described by rc = 4iraa3/3kT (2) Inserting 0.105 f 0.005 nm for r C H one obtains at all concentrations a value of a, commonly taken as the diameter of the diffusing particle, of 0.45 f 0.05 nm, which certainly is less than the actual dimensions of the single nucleotide. Taking the isotropic rotating sphere as a valid approximation for the motion of 5'-AMP in water, rc is described by rc = 4iraa3/3kT (2) Inserting 0.105 f 0.005 nm for r C H one obtains at all concentrations a value of a, commonly taken as the diameter of the diffusing particle, of 0.45 f 0.05 nm, which certainly is less than the actual dimensions of the single nucleotide.…”

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Simple criteria for distinguishing between inner- and outer-sphere electrode reaction mechanisms

Weaver¹,

Anson²

1975

J. Am. Chem. Soc.

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4403 0 . 5 -0 0.5 1.0 conc.5'-AmP (M 1-Figure 1. Viscosity of aqueous 5'-AMP solutions as a function of concentration (J": 7.0 & 0.4). 0.1 u 0.2 0.5 1.0 2.0 Yp(CP-1)-Figure 2. Double log plot of the average longitudinal I3C relaxation rates of S'-AMP'J vs. the reciprocal viscosity of the solutions: points, average of C-I' to C-4'; crosses, average of C-2, C-8. nucleotide one calculates the rotational correlation time rc in the extreme narrowing case from3 1/Tl = Nh2yC2yH2rCH-6rc(1) with N the number of protons bound to the carbon and yc and YH the magnetogyric ratios of the two nuclear spins involved. Taking the isotropic rotating sphere as a valid approximation for the motion of 5'-AMP in water, rc is described byInserting 0.105 f 0.005 nm for r C H one obtains at all concentrations a value of a, commonly taken as the diameter of the diffusing particle, of 0.45 f 0.05 nm, which certainly is less than the actual dimensions of the single nucleotide. The relaxation times of the base carbons at the different concentrations are therefore determined by the macroscopic viscosity, and it is unnecessary to invoke any specific microscopic model to explain the experimental results. On the other hand, the relaxation rates of the sugar carbon, which possess several possibilities of internal motion, depend on two correlation times: the correlation time for overall molecular reorientation which increases with increasing viscosity and a correlation time for the internal motions which to a first approximation should not depend on the vis~osity.~J It is then clear that the effect of the internal motions can only be observed in the more concentrated solutions, that is when the overall reorientation is slowed down.Rhodes and SchimrneF measured the energy of activa-tion for the rotation around the glycosidic bond (syn e anti equilibrium) in some purine (@)ribosides to be 6.2 kcal mol-'. Therefore the segmental motion may not come from rotation around the glycosidic bond. Roder et aL7 have determined the activation energy for the conformational mobility of the furanoside ring of the ribose moiety, as for example described by the N * S model of Altona and Sundaralingams by variable temperature I3C relaxation measurements and comparison with the 2',3'-isopropylidene nucleosides to be 4.7 f 0.5 kcal mol-I. Assuming that these results are applicable to 5'-AMP one must conclude that the deviations observed in the more concentrated solutions for the relaxation rates of the sugar carbons from those of the base should not be explained by a greater diffusive mobility of the ribosephosphate moiety around the glycosidic bond but rather by transitions between the different possible conformations of the ribose ring. References and Notes(1) W. D. Hamlll, Jr., R. J. Pugmlre, and D. M. Grant, J. Am. Chem. SOC., 96, (2) A. Allerhand. D. Doddreil, and R. Komoroskl, J. Chem. Phys., 55, 189 (3) A. Abraaam, "The Principles of Nuclear Magnetism", Oxford University 2885 (1974). (1 97 1). Press, London, 1961, p 300. 5456 (1974). (4) D. Doddrell and A. Aller...

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“…reactions which occur in potential ranges which have substantial specific adsorption, Eq. (V-14) caniot be used to correct the 02 values for the presence of the chromium ion even as an approximation. These reactions include the oxidation of £Cr(H 2 0)6 1 2+ or[C1+ in mixed soluxtions of chloride-perchlorate, the oxidation of [Cr(H2) 6 2+or 2or [Cr(H 2 0) 6 ]Br + in mixed bromide-perchlorate solutions, and the reduction of [Cr(H 2 0) Br]2+ in mixed bromide-perchlorate solutions.…”

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The Electrode Kinetics of the Chromous-Chromic Couple

Donovan¹,

Yeager²

1969

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EFFECT OF CHLORIDE ON THE KINETICS OF ELECTROÖXIDATION OF CHROMIUM(II) IN ACIDIC PERCHLORATE MEDIUM¹

Cited by 40 publications

References 0 publications

V²⁺/V³⁺ Redox Kinetics on Glassy Carbon in Acidic Electrolytes for Vanadium Redox Flow Batteries

V²⁺/V³⁺ Redox Kinetics on Glassy Carbon in Acidic Electrolytes for Vanadium Redox Flow Batteries

Simple criteria for distinguishing between inner- and outer-sphere electrode reaction mechanisms

The Electrode Kinetics of the Chromous-Chromic Couple

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EFFECT OF CHLORIDE ON THE KINETICS OF ELECTROÖXIDATION OF CHROMIUM(II) IN ACIDIC PERCHLORATE MEDIUM1

Cited by 40 publications

References 0 publications

V2+/V3+ Redox Kinetics on Glassy Carbon in Acidic Electrolytes for Vanadium Redox Flow Batteries

V2+/V3+ Redox Kinetics on Glassy Carbon in Acidic Electrolytes for Vanadium Redox Flow Batteries

Simple criteria for distinguishing between inner- and outer-sphere electrode reaction mechanisms

The Electrode Kinetics of the Chromous-Chromic Couple

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EFFECT OF CHLORIDE ON THE KINETICS OF ELECTROÖXIDATION OF CHROMIUM(II) IN ACIDIC PERCHLORATE MEDIUM¹

V²⁺/V³⁺ Redox Kinetics on Glassy Carbon in Acidic Electrolytes for Vanadium Redox Flow Batteries

V²⁺/V³⁺ Redox Kinetics on Glassy Carbon in Acidic Electrolytes for Vanadium Redox Flow Batteries