Polarographic behavior of iodine in non-aqueous solvents

Nakata, Ryuji; Okazaki, Satoshi; Fujinaga, Taitiro

doi:10.1016/s0022-0728(81)80358-0

Cited by 7 publications

(4 citation statements)

References 16 publications

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“…Figures and highlight key information from SECCM on spatially resolved ET kinetics that is lost in macroscale measurements involving polycrystalline platinum electrodes. Figure b shows that the apparent Tafel slopes display little variation across the surface (see also Figure S2 in the SI), with all grains between 100 and 120 mV per decade, suggesting that the rate determining step ,, in the mechanism in all grains is the first electron transfer (nominally 120 mV per decade).…”

Section: Results and Discussionmentioning

confidence: 99%

“…Although alternatives to platinum as the CE material and the triiodide (I 3 – )/iodide (I – ) redox couple as the mediator have been suggested, these remain the most common components . However, compared to other processes occurring in DSSCs, there are relatively few mechanistic studies of the reduction of I 3 – to I – on platinum in various media. − In this paper, we show that the rate of this reaction in room temperature ionic liquids (RTILs) is strongly influenced by the local structure of the Pt electrodes and identify the optimal surface for electrocatalysis.…”

Section: Introductionmentioning

confidence: 99%

“…Figure 5b shows that the apparent Tafel slopes display little variation across the surface (see also Figure S2 in the SI), with all grains between 100 and 120 mV per decade, where the meniscus contact area was estimated as <3 μm in diameter (i.e., of the order of the probe size) where the DC was perturbed the most (at grain boundaries, shown in Figure 3e). suggesting that the rate determining step 6,8,29 in the mechanism in all grains is the first electron transfer (nominally 120 mV per decade).…”

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confidence: 99%

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Spatially Resolved Electrochemistry in Ionic Liquids: Surface Structure Effects on Triiodide Reduction at Platinum Electrodes

2014

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ABSRACT:Understanding the relationship between electrochemical activity and electrode structure is vital for improving the efficiency of dye-sensitized solar cells. Here, the reduction of triiodide to iodide in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF 4 ]) room temperature ionic liquid (RTIL) is investigated on polycrystalline platinum using scanning electrochemical cell microscopy (SECCM) and correlated to the crystallographic orientation from electron backscatter diffraction (EBSD). Although the rate determining step in all grains was the first electron transfer, significant grain-dependent variations in activity were revealed, with grains with a dominant (110) crystallographic character exhibiting higher catalytic activity compared to those with a major (100) orientation. The SECCM technique is demonstrated to resolve heterogeneity in activity, highlighting that methods incorporating 2 polycrystalline electrodes miss vital details for understanding and optimizing electrocatalysts.An additional advantage of the SECCM over single crystal techniques is its ability to probe high index facets.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Spatially Resolved Electrochemistry in Ionic Liquids: Surface Structure Effects on Triiodide Reduction at Platinum Electrodes

2014

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“…[18,19] The iodide/triiodide couple has been studied by rotating disk electrode and cyclic voltammetry (CV) in CH3CN with studies performed on Pt [22,23] and Hg. [24] Besides CH3CN, other media have also been studied, e.g., Compton studied the couple in ionic liquids (ref [25] and references therein). While the existence of an intermediate has been postulated from electrochemical kinetic measurements, [22,23,25,26] we are not aware of direct evidence of the existence of a radical intermediate under electrochemical conditions; the evidence described above is for the formation of I2 •ˉ under photoelectrochemical conditions on TiO2.…”

Section: Introductionmentioning

confidence: 99%

Evidence of Radical Intermediate Generated in the Electrochemical Oxidation of Iodide

Fernando¹,

Parajuli²,

Barakoti³

et al. 2019

J. Mex. Chem. Soc.

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We present evidence of the generation of radical ion formation during the oxidation of iodide on a fluorine doped tin oxide (FTO) electrode in acetonitrile. The cyclic voltammograms for the oxidation of iodide and triiodide on FTO are significantly different as in the case of the oxidation of Pt electrode. These differences are assigned to kinetic differences on the FTO surface that require significant over potentials to drive the oxidation of iodide and triiodide. We propose that at the highly positive potentials the iodine radical intermediate, I·, becomes thermodynamically stable at FTO. The radical nature of the intermediate was verified by the formation of radicals of the usual traps of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and 2,2,5,5 tetramethyl-1-pyrroline N-oxide (TMPO) when these were added to an electrolyzed solution. Irradiation of an iodine solution causes the homolytic cleavage of I2 and yields the same radical intermediate with TMPO as in the electrolysis experiment. Similar results were obtained from the electrolysis of bromide solutions upon addition of TMPO. Short term electrolysis (< 1 h) gives triiodide as a final product while long-term electrolysis (> 17 h) yields additional byproducts. Byproducts were determined to be organoiodines by gas chromatography-mass spectrometry (GC-MS). Overall, our results are consistent with iodine atoms reacting with the electrolyte during electrolysis at the FTO electrode and with a sequential two-electron transfer process.

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