Kinetic study of the hydrogen evolution reaction in slightly alkaline electrolyte on mild steel, goethite and lepidocrocite

Hedenstedt, Kristoffer; Simic, Nina; Wildlock, Mats; Ahlberg, Elisabet

doi:10.1016/j.jelechem.2016.11.011

Cited by 21 publications

(42 citation statements)

References 36 publications

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“…The cathodic current efficiency is plotted for electrodes previously run in the sodium chlorate process. The surfaces of the electrodes consist of goethite (a-FeOOH) and lepidocrocite (c-FeOOH) [17] cathodic current efficiency is maximised. Diversion from this value (approximately 71°C) will decrease the current efficiency and increase the power consumption.…”

Section: Discussionmentioning

confidence: 99%

“…The conditions during full-scale operation and the surface analysis of the electrodes have been described earlier [17]. The electrode from plant 1 had goethite on the surface, and the electrode from plant 2 had lepidocrocite.…”

Section: Electrodes Previously Used In Sodium Chlorate Plantsmentioning

confidence: 99%

“…This calculation yields an average cathodic current efficiency over the first 200 h. The power consumption, P, is calculated according to (17),…”

Section: Power Consumptionmentioning

confidence: 99%

“…The current efficiency has been studied in some publications, but the most common approach is to study the cell or electrode potential and oxygen production [9,10,[12][13][14][15][16][17]. It has also been reported that the time it takes to reach stable conditions in a chlorate cell or at the surface of a chlorate cathode is significantly long [8].…”

Section: Introductionmentioning

confidence: 99%

“…Different process conditions were evaluated with regard to performance, such as the temperature of the electrolyte, and the sodium dichromate and sodium sulphate concentrations in the electrolyte. In addition, a surface characterisation of the corrosion products formed on the cathodes was performed since it was shown in a recent study that two different types of iron oxyhydroxides found on chlorate cathodes actually influenced the time that was required to reach full current efficiency [17].…”

Section: Introductionmentioning

confidence: 99%

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Current efficiency of individual electrodes in the sodium chlorate process: a pilot plant study

et al. 2017

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Current efficiency in the sodium chlorate process is a key issue in the evaluation of the power consumption. A pilot cell unit for executing the sodium chlorate process was constructed to study the current efficiency of the anode and cathode separately. The effects of sodium dichromate and sodium sulphate concentrations and the electrolyte temperature on the anode and cathode current efficiencies were studied. Corrosion products formed on the mild steel cathodes after their removal from the cell were characterised using X-ray diffraction and infrared spectroscopy. The results show that the cathodic current efficiency increases with increasing dichromate concentrations in the electrolyte until approximately 5 g dm -3 is reached. At this optimum concentration of dichromate, the presence of sulphate ions decreases the cathodic current efficiency. For moderate increases in temperature, the cathodic current efficiency increases, but oxygen evolution is promoted, and the power consumption also increases. Surface characterisation of the electrodes after their exposure to air shows two primary types of behaviour, depending on the process parameters. At low dichromate concentrations, amorphous corrosion layers are formed, while at higher concentrations, reduced forms of iron hydroxides, i.e., ''green rust'', are identified. Although the electrodes were positioned at the open circuit potential for 40 min before their removal from the cell, chromium remains on the cathode surface. This result might explain the corrosion-inhibiting effect of the addition of chromate to the electrolyte. The results from this study can be used to optimise operating procedures in real plants, decrease the energy consumption and minimise the environmental impact of these processes.Electronic supplementary material The online version of this article

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Section: Discussionmentioning

confidence: 99%

Section: Electrodes Previously Used In Sodium Chlorate Plantsmentioning

confidence: 99%

“…This calculation yields an average cathodic current efficiency over the first 200 h. The power consumption, P, is calculated according to (17),…”

Section: Power Consumptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Current efficiency of individual electrodes in the sodium chlorate process: a pilot plant study

et al. 2017

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Electrochemical reduction and re‐oxidation behavior of α, β, and γ‐iron oxy‐hydroxide films on electrodes

Sugae

Asakura

Doi

et al. 2018

Materials & Corrosion

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To clarify the effect of rust on the corrosion of steel exposed to an atmosphere containing chloride, the electrochemical reduction and re‐oxidation behavior of α, β, and γ‐FeOOH is studied. Films are formed on gold electrodes and are electrochemically reduced at several potentials, thus simulating the corrosion potential under wet and dry conditions. The current flowing through the β‐FeOOH is the highest among the three films. The β‐FeOOH is reduced to Fe3−δO4 at a noble potential of less than −300 mV, relative to a standard hydrogen electrode (SHE) and is reductively dissolved to Fe2+ at a noble potential of less than −100 mV (SHE). The formed Fe3−δO4 is not reformed to β‐FeOOH during re‐oxidation. It is found that the β‐FeOOH plays an important role in the cathodic reaction, acting as an oxidant, and can significantly affect the corrosion of steel in the atmosphere.

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Understanding Selectivity in the Chlorate Process: A Step towards Efficient Hydrogen Production

Gomes

Busch²,

Wildlock

et al. 2018

ChemistrySelect

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Chlorate production is a highly energy demanding industrial process, where chlorate formation is accompanied with hydrogen formation on the cathode. To ensure a high cathodic current efficiency, sodium dichromate is added to the chlorate electrolyte to avoid reduction of hypochlorite formed as a reaction intermediate in the process. However, chromate is highly toxic to humans and environment, and therefore a replacement is desired. A model system with ex situ formed chromium oxide/hydroxide films were used to study hypochlorite reduction and hydrogen evolution. The experimental results demonstrate that the hypochlorite reduction is fully blocked while hydrogen evolution readily occurs. However, in the presence of hypochlorite the hydrogen evolution reaction is inhibited. By combining experimental findings with density functional theory (DFT) calculations, the mechanism of hypochlorite reduction was revealed and the reason for inhibition by the deposited chromium(III) film was demonstrated. Based on these results possible replacements for chromate are suggested.

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Kinetic study of the hydrogen evolution reaction in slightly alkaline electrolyte on mild steel, goethite and lepidocrocite

Cited by 21 publications

References 36 publications

Current efficiency of individual electrodes in the sodium chlorate process: a pilot plant study

Current efficiency of individual electrodes in the sodium chlorate process: a pilot plant study

Electrochemical reduction and re‐oxidation behavior of α, β, and γ‐iron oxy‐hydroxide films on electrodes

Understanding Selectivity in the Chlorate Process: A Step towards Efficient Hydrogen Production

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