Bromate electroreduction via autocatalytic redox mediation: EC” mechanism. Theory for stationary 1D regime. Current limitation by proton transport
Process of the bromate anion reduction in the presence of a very low bromine concentration from an acidic solution for the one-dimensional transport under steady-state conditions has been analyzed theoretically. Bromate being non-electroactive in the potential range under consideration, its transfor...
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Veröffentlicht in: | Electrochimica acta 2016-08, Vol.210, p.950-962 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Process of the bromate anion reduction in the presence of a very low bromine concentration from an acidic solution for the one-dimensional transport under steady-state conditions has been analyzed theoretically. Bromate being non-electroactive in the potential range under consideration, its transformation takes place via the redox cycle composed by the reversible couple, Br2/Br−, and the irreversible comproportionation reaction inside the solution phase between BrO3−, Br− and protons which regenerates Br2. Specific feature of this process compared to the conventional EC' mechanism is the progressive increase in the overall amount of the components of the redox couple owing to consumed bromate. As a result, this novel EC” mechanism possesses autocatalytic properties so that even a trace amount of bromine in the bulk solution may result in very high current densities, up to the those limited by the diffusion of the principal solution components, bromate and protons. Unlike our previous study of this system carried out for excess of protons compared to bromate [Electrochim. Acta, 173 (2015) 779-795] we consider the opposite situation where bromate is in great excess compared to protons so that the transport of the latter component from the bulk solution limits the maximal current. Approximate analytical formulas have been derived for all characteristics of the system based on the condition of either a relatively weak current or a thin kinetic layer compared to the diffusion one. Behavior of the system depends crucially on the relation between the diffusion layer thickness, zd, and the kinetic layer thickness, zk (determined by the rate of the homogeneous reaction). For a very thin diffusion layers: zd |
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ISSN: | 0013-4686 1873-3859 |
DOI: | 10.1016/j.electacta.2016.06.010 |