Studies Relating to Electrolytic Preparation of Potassium Bromate

Vasudevan, Subramanyan

doi:10.1021/ie071554e

Cited by 5 publications

(6 citation statements)

References 11 publications

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“…Without the Na2Cr2O7 additive (but otherwise the same conditions), the Faradaic efficiency dropped to 10±1%, indicating the important role of Na2Cr2O7 to prevent rxns 8 -11 by forming a polyoxide cathodic barrier, as reported elsewhere. 29,31,32,33,34,35,36 In the second operational mode (Figure 2d), without Na2Cr2O7, the Faradaic efficiency was 72±2% without stirring, and it dropped to 13±1% with stirring, demonstrating the effectiveness of the spontaneous phase separation between the oxidized electrolyte and the rest of the electrolyte in suppressing the cathodic loss reactions (rxns 8 -11). This encouraging result suggests that the Faradaic efficiency may be further enhanced by removing the oxidized electrolyte from the bottom of the cell, as illustrated in Figure 1.…”

Section: Electrolytic Processmentioning

confidence: 97%

“…Operation at 60C and pH 8 was found to provide optimal conditions to suppress oxygen evolution (rxn 7) and achieve close to 100% Faradic efficiency for bromate production (rxn 6). 31,32 To suppress the cathodic backward reactions that reduce the oxidized bromine species back to bromide (rxns 8 -11), a small amount (1-3 g/L) of sodium dichromate (Na2Cr2O7) is added to the sodium bromide (NaBr) aqueous electrolyte. The dichromate anions (Cr2O7 2-) are reduced and deposited on the cathode, coating it with a semipermeable chromium hydroxide layer (illustrated by the green layer in Figure 1) that suppresses the cathodic loss reactions (rxns 8 -11), while allowing the HER to occur without hindrance.…”

Section: Conceptmentioning

confidence: 99%

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Electrochemical – chemical cycle for high-efficiency decoupled water splitting in a near-neutral electrolyte

Slobodkin,

Davydova,

Sananis

et al. 2023

Preprint

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Green hydrogen produced by water splitting using renewable electricity is essential to achieve net-zero carbon emissions. Present water electrolysis technologies are uncompetitive with low-cost grey hydrogen produced from fossil fuels, limiting their scale-up potential. Disruptive processes that decouple the hydrogen and oxygen evolution reactions and produce them in separate cells or different stages emerge as a prospective route to reduce system cost by enabling operation without expensive membranes and sealing components. Some of them divide the hydrogen or oxygen evolution reactions into electrochemical and chemical sub-reactions, leading the way to high efficiency. However, high efficiency was demonstrated only in a batch process with thermal swings that present operational challenges. This work introduces a breakthrough process that produces hydrogen and oxygen in separate cells and supports high-efficiency continuous operation in a membraneless system. We demonstrate high Faradaic and electrolytic efficiency and high-rate operation in a near-neutral electrolyte of NaBr in water.

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Section: Electrolytic Processmentioning

confidence: 97%

Section: Conceptmentioning

confidence: 99%

Electrochemical – chemical cycle for high-efficiency decoupled water splitting in a near-neutral electrolyte

Slobodkin,

Davydova,

Sananis

et al. 2023

Preprint

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“…Operation at 60 °C and pH 8 was found to provide optimal conditions to suppress oxygen evolution (reaction 7) and achieve close to 100% faradaic efficiency for bromate production (reaction 6) 26 , 27 . To suppress the cathodic backward reactions (reactions 8–11), a small amount (1–3 g l –1 ) of sodium dichromate (Na 2 Cr 2 O 7 ) is added to the sodium bromide (NaBr) aqueous electrolyte.…”

Section: Conceptmentioning

confidence: 99%

“…But instead of using a nickel (oxy)hydroxide anode, we propose a SRC that supports continuous operation and an isothermal process with high efficiency and at a high rate. The reduced SRC (red) is oxidized in an electrochemical reaction (red → ox + ne -, where n is the number of electrons (e -)) that complements the HER without Article https://doi.org/10.1038/s41563-023-01767-y Operation at 60 °C and pH 8 was found to provide optimal conditions to suppress oxygen evolution (reaction 7) and achieve close to 100% faradaic efficiency for bromate production (reaction 6) 26,27 . To suppress the cathodic backward reactions (reactions 8-11), a small amount (1-3 g l -1 ) of sodium dichromate (Na 2 Cr 2 O 7 ) is added to the sodium bromide (NaBr) aqueous electrolyte.…”

Section: Conceptmentioning

confidence: 99%

Electrochemical and chemical cycle for high-efficiency decoupled water splitting in a near-neutral electrolyte

Slobodkin,

Davydova,

Sananis

et al. 2024

Nat. Mater.

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Green hydrogen produced by water splitting using renewable electricity is essential to achieve net-zero carbon emissions. Present water electrolysis technologies are uncompetitive with low-cost grey hydrogen produced from fossil fuels, limiting their scale-up potential. Disruptive processes that decouple the hydrogen and oxygen evolution reactions and produce them in separate cells or different stages emerge as a prospective route to reduce system cost by enabling operation without expensive membranes and sealing components. Some of these processes divide the hydrogen or oxygen evolution reactions into electrochemical and chemical sub-reactions, enabling them to achieve high efficiency. However, high efficiency has been demonstrated only in a batch process with thermal swings that present operational challenges. This work introduces a breakthrough process that produces hydrogen and oxygen in separate cells and supports continuous operation in a membraneless system. We demonstrate high faradaic and electrolytic efficiency and high rate operation in a near-neutral electrolyte of NaBr in water, whereby bromide is electro-oxidized to bromate concurrent with hydrogen evolution in one cell, and bromate is chemically reduced to bromide in a catalytic reaction that evolves oxygen in another cell. This process may lead the way to high-efficiency membraneless water electrolysis that overcomes the limitations of century-old membrane electrolysis.

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“…In particular, such transformations were carried out inside devices containing membrane-electrode assemblies or analogous arrangements where the bromide oxidation took place where bromate was a target or byproduct. Such studies were performed for bromate electrosynthesis [1][2][3], production of "active bromine" for disinfection [4,5], electrolysis of seawater for hydrogen production [6] as well as the electrochemical treatment of wastewater with the use of the BDD electrodes [7]. The inverse process of the bromate electroreduction was also studied by researchers, primarily in the context of bromate removal generated during water treatment by ozone [8].…”

Section: Introductionmentioning

confidence: 99%

Evolution of the Bromate Electrolyte Composition in the Course of Its Electroreduction inside a Membrane–Electrode Assembly with a Proton-Exchange Membrane

Konev,

Zader,

Vorotyntsev

2023

IJMS

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The passage of cathodic current through the acidized aqueous bromate solution (catholyte) leads to a negative shift of the average oxidation degree of Br atoms. It means a distribution of Br-containing species in various oxidation states between −1 and +5, which are mutually transformed via numerous protonation/deprotonation, chemical, and redox/electrochemical steps. This process is also accompanied by the change in the proton (H+) concentration, both due to the participation of H+ ions in these steps and due to the H+ flux through the cation-exchange membrane separating the cathodic and anodic compartments. Variations of the composition of the catholyte concentrations of all these components havehas been analyzed for various initial concentrations of sulfuric acid, cA0 (0.015–0.3 M), and two values of the total concentrations of Br atoms inside the system, ctot (0.1 or 1.0 M of Br atoms), as functions of the average Br-atom oxidation degree, x, under the condition of the thermodynamic equilibrium of the above transformations. It is shown that during the exhaustion of the redox capacity of the catholyte (x pass from 5 to −1), the pH value passes through a maximum. Its height and the corresponding average oxidation state of bromine atoms depend on the initial bromate/acid ratio. The constructed algorithm can be used to select the initial acid content in the bromate catholyte, which is optimal from the point of view of preventing the formation of liquid bromine at the maximum content of electroactive compounds.

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Studies Relating to Electrolytic Preparation of Potassium Bromate

Cited by 5 publications

References 11 publications

Electrochemical – chemical cycle for high-efficiency decoupled water splitting in a near-neutral electrolyte

Electrochemical – chemical cycle for high-efficiency decoupled water splitting in a near-neutral electrolyte

Electrochemical and chemical cycle for high-efficiency decoupled water splitting in a near-neutral electrolyte

Evolution of the Bromate Electrolyte Composition in the Course of Its Electroreduction inside a Membrane–Electrode Assembly with a Proton-Exchange Membrane

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