Bromate Anion Reduction at Rotating Disk Electrode in Steady State under Excess of Protons: Numerical Solution of the Convective Diffusion Equations at Equal Diffusion Coefficients of Components

A. E. Antipov A. E. Antipov , M. A. Vorotyntsev M. A. Vorotyntsev
Российский электрохимический журнал
Abstract / Full Text

Process of bromate anion reduction at rotating disk electrode in steady state occurring owing to catalytic cycle is analyzed theoretically. The cycle consists of bromine/bromide reversible redox-couple and comproportionation irreversible reaction. Because of the cycle autocatalytic character (EC''-mechanism: Electrochim. Acta, 2015, 173, 779), the passing current can be enormously large at bromate high bulk concentration (up to the bromate limited diffusion current to electrode surface) even when the bromine concentration in the bulk solution is negligibly small. Unlike the previous theoretical studies of the problem (Electrochim. Acta, 2015, 173, 779; Doklady Chemistry, 2016, 468, 141; Russ. J. Electrochem., 2016, 52, No. 10, 925), in this work the component concentration distributions during the process at a prescribed value of the passing current are calculated on the basis of the convective diffusion equations for bromine and the bromate and bromide anions for the first time. Under the assumption that the component diffusion coefficients are equal, exact interrelations between these concentration profiles are derived, which allows reducing the problem to the solving of nonlinear equation of second order for the bromide concentration with boundary conditions at the electrode surface and in the solution bulk. Thus, obtained concentration profiles of all components for a corresponding set of current densities are used to calculate of steady-state polarization curves, as well, as the maximal current dependence on the rotating disk electrode velocity.

Author information
  • Mendeleev University of Chemical Technology, Miusskaya pl. 9, Moscow, 125047, Russia

    A. E. Antipov & M. A. Vorotyntsev

  • Lomonosov State University, Leninskie Gory 1, Moscow, 119992, Russia

    A. E. Antipov & M. A. Vorotyntsev

  • Institute of Problems of Chemical Physics, Russian Academy of Sciences, pr. akad. Semenova 1, Chernogolovka, Moscow oblast, 142432, Russia

    M. A. Vorotyntsev

  • Institut de la Chimie Moleculaire, Université de Bourgogne, Dijon, France

    M. A. Vorotyntsev

  1. Tolmachev, Y.V., Piatkivskyi, A., Ryzhov, V.V., Konev, D.V., and Vorotyntsev, M.A., Energy cycle based on a high specific energy aqueous flow battery and its potential use for fully electric vehicles and for direct solar-to-chemical energy conversion, J. Solid State Electrochem., 2015, vol. 19, p. 2711.
  2. Vorotyntsev, M.A., Konev, D.V., and Tolmachev, Y.V., Electroreduction of halogen oxoanions via autocatalytic redox mediation by halide anions: novel EC"mechanism theory for stationary 1D regime, Electrochim. Acta, 2015, vol. 173, p.779.
  3. Antipov, A.E. and Vorotyntsev, M.A., Bromate anion electroreduction on inactive RDE under steady-state conditions. Numerical study of ion transport processes and comproportionation reaction, Russ. J. Electrochem., 2016, vol. 52, №10, 925.
  4. Antipov, A. E., Vorotyntsev, M. A., Tolmachev, Y. V., Antipov, E.M., and Aldoshin, S.M., Electroreduction of bromate anion in acidic solutions at the inactive rotating disc electrode under steady-state conditions: Numerical modeling of the process with bromate anions being in excess compared to protons, Doklady Chemistry, 2016, vol. 468, p.141.
  5. Nernst, W., Theorie der reaktionsgeschwindigkeit in heterogenen systemen, Z. Phys. Chem., 1904, vol. 47, p.52.
  6. Nernst, W. and Merriam, E.S., Zur theorie des reststroms. (nach versuchen von Herrn Merriam), Z. Phys. Chem., 1905, vol. 53, p.235.
  7. Bard, A.J. and Faulkner, L.R., Electrochemical methods, 2nd ed., New York: Wiley, 2001.
  8. Levich, V.G., Physicochemical hydrodynamics, New York: Prentice Hall, Englewood Cliffs, 1962.
  9. Damaskin, B.B., Petrii, O.A., and Tsirlina, G.A., Elektrokhimiya (Electrochemistry), Moscow: Khimiya, Koloss, 2006.
  10. Cortes, C.E.S. and Faria, R.B., Revisiting the kinetics and mechanism of bromate-bromide reaction, J. Braz. Chem. Soc., 2001, vol. 12, p.775.
  11. Cortes, C.E.S. and Faria, R.B., Kinetics and mechanism of bromate-bromide reaction catalyzed by acetate, Inorg. Chem., 2004, vol. 43, p. 1395.
  12. Schmitz, G., Kinetics of the bromate-bromide reaction at high bromide concentrations, Int. J. Chem. Kinet., 2007, vol. 39, p.17.
  13. Pugh, W., The stability of bromic acid and its use for the determination of bromide in bromates and in chlorides, Trans. Roy. Soc. South Afr., 1932, vol. 20, p.327.
  14. Antipov, A.E. and Vorotyntsev, M.A., Generalized Nernst layer model for convective-diffusional transport. Numerical solution for bromate anion electroreduction on inactive RDE under steady state conditions, Russ. J. Electrochem., 2017, vol. 53 (in press).