The adsorption, orientation and electrochemical oxidation of hydroquinone at smooth platinum electrodes

Chia, Victor K. F.; Soriaga, Manuel P.; Hubbard, Arthur T.

doi:10.1016/0368-1874(84)87059-8

Cited by 20 publications

(10 citation statements)

References 30 publications

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“…CN -*• diffusion and pump out (6) In addition CN(u =1) can be quenched to CN(c = 0) by H2, M, or C2N2. However, we have elected to discount any effects that CN(y = 1) might introduce on the rate constant measurements for the following reasons.…”

Section: Resultsmentioning

confidence: 99%

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Kinetics of gas-phase cyanogen by diode laser absorption

Balla¹,

Pasternack²

1987

J. Phys. Chem.

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Absolute rate constants for the reaction of CN with H2, D2, and CH4 are reported by using a diode laser to probe CN disappearance and HCN growth. The reactions were studied at room temperature over the pressure range 1-200 Torr. The following rate constants were obtained by monitoring the decay of CN ( 2 +) on the P(7) ( ' = 1 <-v" = 0) transition at 2015.22 cm'1: fc(CN+H2) = (2.6 ± 0.3) X 10'14, k(CN+D2) = (7.2 ± 0.9) X 10'15, and k(CN+CH4) = (7.8 ± 0.9) X 10'13 cm3 s'1, where the uncertainties represent ±2 . The growth of HCN was monitored on the (0,0,1) <-(0,0,0) P(10) transition at 3280.987 cm'1 at total pressures of 5-100 Torr. We obtained the rate constant fc(CN+H2) = (2.2 ± 0.9) X 10"14 cm3 s'1, where the uncertainty represents ±2 . Transition-state-theory calculations based on an ab initio potential energy surface were used to determine the kinetic isotope effect for the reaction of CN with H2 and D2. The predicted value of k(H2)/k(D2) = 3.55 is in excellent agreement with our experimental ratio of 3.6. The integrated line strength for the P(7) ( ' = 1 •-v" = 0) transition of CN ( 2 +) was measured under low-pressure conditions where only natural and Doppler broadenings contribute to the half-width. The measured value, assuming = 2 in the 193-nm photolysis of C2N2, is (2.0 ± 0.8) X 10'19 cm2 molecule'1 cm'1, where the uncertainty represents ±1 .

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Section: Resultsmentioning

confidence: 99%

“…Figure6. Plot of the logarithm of the decay minus the signal for the growth of HCN vs. time at 298 K. The conditions of Figure5were used to obtain this plot.…”

mentioning

confidence: 99%

Kinetics of gas-phase cyanogen by diode laser absorption

Balla¹,

Pasternack²

1987

J. Phys. Chem.

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“…Thus, our complex signal at 1650-1675 cm À1 is probable due to the vibration of the carbonyl group of a benzoquinone and has to be taken into account as a second reaction pathway in the course of TYH + electrooxidation on platinum. Reports about the adsorption and electrooxidation of phenols and hydroquinones on platinum sc surfaces using ultra-high vacuum methodologies and conventional electrochemical techniques [42][43][44][45] have been published in the late 1980s. Either if there was a random orientation of the molecule at the surface or a defined adsorption (aromatic ring parallel or perpendicular orientation), the phenol or hydroquinone molecule produces quinone derivates in acid solution at a smooth or a rough platinum surface [46][47][48].…”

Section: Products Assignmentmentioning

confidence: 99%

FTIR studies of tyrosine oxidation at polycrystalline Pt and Pt(111) electrodes

Zinola

Rodrı́guez

Arévalo

et al. 2005

Journal of Electroanalytical Chemistry

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“…Central to the molecular orientation studies was the measurement of the surface coverage or packing density (G, mol/cm 2 ) of the intact chemisorbed molecules [6,7]. Dihydroxy substituted benzene compounds were popular subject molecules because of the well-characterized electrochemistry [8][9][10][11][12][13][14][15][16][17]. The chemisorption isotherm of H 2 Q on Pt(pc) surfaces has demonstrated that H 2 Q chemisorption is a nonrandom, irreversible process in which chemisorbed species adopts specific orientations depending of the bulk organic solution.…”

Section: Introductionmentioning

confidence: 99%

A DEMS study of the electrocatalytic hydrogenation and oxidation of p-dihydroxybenzene at polycrystalline and monocrystalline platinum electrodes

et al. 2006

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The electrochemical hydrogenation and oxidation of p-dihydroxybenzene (hydroquinone) chemisorbed at polycrystalline Pt, well-ordered Pt(111) and disordered Pt(111) electrodes were studied by differential electrochemical mass spectrometry (DEMS). For comparative purposes, benzene was investigated at polycrystalline Pt. Anodic oxidation yielded only CO 2 as the volatile (DEMS-detectable) product. However, at least three oxidation cycles were necessary for exhaustive oxidation; this indicates that: (i) non-volatile products were generated in the first cycle, (ii) these products either stayed adsorbed or, in part, were re-adsorbed during a cathodic scan into the doublelayer potential region, and (iii) these species were further oxidized on subsequent anodic scans. Electrocatalytic hydrogenation of hydroquinone at polycrystalline Pt followed two parallel (not sequential) paths to generate benzene and cyclohexane: the ''branching ratio'' was heavily in favor of the latter product. The adsorbate can be displaced by CO at potentials in the double layer region. Since no volatile species was observed during this process, the adsorbate is not already reduced; e.g., to benzene. On well-ordered Pt(111), no cyclohexane was produced and only a minuscule fraction of benzene was observed; however, quantitative desorption of (unidentified) non-volatile organic material took place at the negative potential. The disordered Pt(111) surface behaved more like the polycrystalline rather than the monocrystalline surface. The H 2 Q-hydrogenation reaction proceeds more readily on Pt with surface steps and kinks.

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The adsorption, orientation and electrochemical oxidation of hydroquinone at smooth platinum electrodes

Cited by 20 publications

References 30 publications

Kinetics of gas-phase cyanogen by diode laser absorption

Kinetics of gas-phase cyanogen by diode laser absorption

FTIR studies of tyrosine oxidation at polycrystalline Pt and Pt(111) electrodes

A DEMS study of the electrocatalytic hydrogenation and oxidation of p-dihydroxybenzene at polycrystalline and monocrystalline platinum electrodes

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