Surprising dependence of the current density of bromate electroreduction on the microelectrode radius as manifestation of the autocatalytic redox-cycle (EC″) reaction mechanism

Конев, Д. В.; Antipov, A. E.; Petrov, Mikhail M.; Shamraeva, Maria; Воротынцев, М. А.

doi:10.1016/j.elecom.2017.11.006

Cited by 12 publications

(5 citation statements)

References 28 publications

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“…These theoretical predictions on the ability of the redox cycle based on reactions (1a) and (2a) to provide very high discharge current densities were confirmed experimentally for the RDE [13] and microelectrode [14] configurations as well as for the hydrogen-bromate discharge cell [15] The next requirement for applications of bromates in flow batteries is to ensure the backward transformation of the discharge product, bromide solution, into the starting oxidant, bromate, preferably via electrolysis. Experimental examples of the Brelectrooxidation leading to formation of BrO3have been described in literature [16][17][18][19].…”

Section: Introductionmentioning

confidence: 66%

Electrochemically driven evolution of Br-containing aqueous solution composition

Petrov

Конев

Kuznetsov

et al. 2019

Journal of Electroanalytical Chemistry

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Section: Introductionmentioning

confidence: 66%

Electrochemically driven evolution of Br-containing aqueous solution composition

Petrov

Конев

Kuznetsov

et al. 2019

Journal of Electroanalytical Chemistry

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“…These theoretical predictions were fully confirmed later by experimental studies of bromate reduction for various electrochemical configurations [50,51], including the most intriguing conclusion of a drastic increase in the current for a less intensive convection.…”

Section: Introductionmentioning

confidence: 57%

A Hydrogen-Bromate Flow Battery as a Rechargeable Chemical Power Source

et al. 2022

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The hydrogen-bromate flow battery represents one of the promising variants for hybrid power sources. Its membrane-electrode assembly (MEA) combines a hydrogen gas diffusion anode and a porous flow-through cathode where bromate reduction takes place from its acidized aqueous solution: BrO3− + 6 H+ + 6 e− = Br− + 3 H2O (*). The process of electric current generation occurs on the basis of the overall reaction: 3 H2 + BrO3− = Br− + 3 H2O (**), which has been studied in previous publications. Until this work, it has been unknown whether this device is able to function as a rechargeable power source. This means that the bromide anion, Br−, should be electrooxidized into the bromate anion, BrO3−, in the course of the charging stage inside the same cell under strongly acidic conditions, while until now this process has only been carried out in neutral or alkaline solutions with specially designed anode materials. In this study, we have demonstrated that processes (*) and (**) can be performed in a cyclic manner, i.e., as a series of charge and discharge stages with the use of MEA: H2, Freidenberg H23C8 Pt-C/GP-IEM 103/Sigracet 39AA, HBr + H2SO4; square cross-section of 4 cm2 surface area, under an alternating galvanostatic mode at a current density of 75 mA/cm2. The coulombic, voltaic and energy efficiencies of the flow battery under a cyclic regime, as well as the absorption spectra of the catholyte, were measured during its operation. The total amount of Br-containing compounds penetrating through the membrane into the anode space was also determined.

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“…These theoretical predictions were later confirmed by experimental studies of this process at the rotating disk electrode [ 4 ] and microelectrodes [ 35 ]. The possibility of strong currents in solutions containing very low bulk-solution concentrations of the catalytic species (Br 2 ) was also supported by a study of hydrogen-bromate MEA electricity sources, which revealed very high current and power densities, as well as almost complete transformation of bromate into bromide, within a single passage of solution through the discharge device [ 7 , 8 ].…”

Section: Theoretical Estimation Of Specific Energy Of a Hydrogen-chlo...mentioning

confidence: 69%

Hydrogen-Chlorate Electric Power Source: Feasibility of the Device, Discharge Characteristics and Modes of Operation

et al. 2022

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A power source based on the current-generating reaction of aqueous chlorate-to-chloride reduction by molecular hydrogen would provide as much as 1150 Wh per 1 L of reagent storage (for a combination of 700 atm compressed hydrogen and saturated aqueous solution of lithium chlorate) at room temperature, but direct electroreduction of chlorate only proceeds with unacceptably high overvoltages, even for the most catalytically active electrodes. In the present study, we experimentally demonstrated that this process can be performed via redox-mediator catalysis by intermediate products of chlorate reduction, owing to their participation in homogeneous com- and disproportionation reactions. A series of current–voltage and discharge characteristics were measured for hydrogen-chlorate membrane–electrode assembly (MEA) cells at various concentrations of chlorate and sulfuric acid under operando spectrophotometric monitoring of the electrolyte composition during the discharge. We established that chlorine dioxide (ClO2) is the key intermediate product; its fraction in the electrolyte solution increases progressively, up to its maximum, equal to 0.4–0.6 of the initial amount of chlorate anions, whereas the ClO2 amount decreases gradually to a zero value in the later stage. In most discharge experiments, the Faradaic yield exceeded 90% (maximal value: 99%), providing approximately 48% chemical energy storage-to-electricity conversion efficiency at maximal power of the discharge (max value: 402 mW/cm2). These results support prospect of a hydrogen-chlorate flow current generator as a highly specific energy-capacity source for airless media.

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Surprising dependence of the current density of bromate electroreduction on the microelectrode radius as manifestation of the autocatalytic redox-cycle (EC″) reaction mechanism

Cited by 12 publications

References 28 publications

Electrochemically driven evolution of Br-containing aqueous solution composition

Electrochemically driven evolution of Br-containing aqueous solution composition

A Hydrogen-Bromate Flow Battery as a Rechargeable Chemical Power Source

Hydrogen-Chlorate Electric Power Source: Feasibility of the Device, Discharge Characteristics and Modes of Operation

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