Electrochemical reduction of hematite-based ceramics in alkaline medium: Challenges in electrode design

Lopes, Daniela; Ivanova, Yu. A.; Kovalevsky, Andrei V.; Sarabando, Artur R.; Frade, J.R.; Quina, Margarida J.

doi:10.1016/j.electacta.2019.135060

Cited by 14 publications

(38 citation statements)

References 32 publications

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“…The cathodic (C) and anodic (A) peaks/shoulders of the reduction and oxidation of the iron species, correspondingly, are listed in Table 1. Generally, the reduction of Fe(III) to Fe(II) species in all the compositions tested takes place around ~−1 V (C 1 ) (Figure 4A,C,E), while the reduction to metallic iron occurs in a superimposed region of the voltammogram associated with the hydrogen evolution reaction (HER) due to the water splitting above ~−1.1 V. HER actively competes for the cathodic current during Fe 0 formation, decreasing considerably the Faradaic efficiencies, as observed in several works [8,9,13,14,19,20], and it is also responsible for the collapse of ceramic cathodes, as in [18]. The present results confirm the non-direct reduction of hematite-based ceramics to metallic iron, involving a reduction of Fe(III) to Fe(II) aqueous species, where Fe 3 O 4 is usually a well-established intermediate Fe(III)/Fe(II) phase, in accordance with Pourbaix diagrams [40,41].…”

Section: Studies Of the Relevant Redox Processes By Cyclic Voltammetrymentioning

confidence: 76%

“…Previous studies have convincingly demonstrated the importance of porosity and a percolating porous network, facilitating electrolyte access and electrochemical reduction [8,18]. SEM micrographs of the porous ceramic cathodes prepared by the emulsification of aqueous suspension of Fe 2 O 3 -TiO 2 powders with liquid paraffin are shown in Figure 2, in comparison with the dense Fe 2 TiO 5 cathode.…”

Section: Structural and Microstructural Features Of The Ceramic Cathodesmentioning

confidence: 79%

“…To prevent unwanted electrochemical contributions, the Ni plate was painted with lacquer (Lacomit Varnish, Agar Scientific, Essex, UK). The configuration of the bulk working electrode (WE) was similar to the one described as NFAg-R in our previous work [18]. The schematic electrochemical cell used for the reduction tests in pellets is described in Figure 1.…”

Section: Methodsmentioning

confidence: 99%

“…reference electrode (RE) connected to the electrochemical cell by a Luggin capillary spiral platinum wire (7.40 cm 2 ) was used as the counter electrode (CE). The experime conditions used during the electrochemical reduction tests were selected based on pr ous results [8,9,18]. The tests were performed for Fe2TiO5, Fe2TiO5•Fe2O3 and Fe2O3 pe (2-3 mm thickness, ~1.1 cm 2 of area), which were used as ceramic cathodes.…”

Section: Methodsmentioning

confidence: 99%

“…Different feedstocks for the electrochemical reduction for steelmaking are now under consideration, including iron-rich waste such as red mud from the aluminium industry [16,17]. The role of some specific elements like Al [18,19] and Mg [20] on the reduction mechanisms of hematite-or magnetite-based compounds were also studied. Recently, the electroreduction of titanium-containing magnetite, Fe 3-x Ti x O 4 , using ironsands as a feedstock, was also studied [21].…”

Section: Introductionmentioning

confidence: 99%

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Prospects of Using Pseudobrookite as an Iron-Bearing Mineral for the Alkaline Electrolytic Production of Iron

et al. 2022

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The alkaline electrolytic production of iron is gaining interest due to the absence of CO2 emissions and significantly lower electrical energy consumption when compared with traditional steelmaking. The possibility of using an iron-bearing pseudobrookite mineral, Fe2TiO5, is explored for the first time as an alternative feedstock for the electrochemical reduction process. To assess relevant impacts of the presence of titanium, similar electroreduction processes were also performed for Fe2TiO5·Fe2O3 and Fe2O3. The electroreduction was attempted using dense and porous ceramic cathodes. Potentiostatic studies at the cathodic potentials of −1.15–−1.30 V vs. an Hg|HgO|NaOH reference electrode and a galvanostatic approach at 1 A/cm2 were used together with electroreduction from ceramic suspensions, obtained by grinding the porous ceramics. The complete electroreduction to Fe0 was only possible at high cathodic polarizations (−1.30 V), compromising the current efficiencies of the electrochemical process due to the hydrogen evolution reaction impact. Microstructural evolution and phase composition studies are discussed, providing trends on the role of titanium and corresponding electrochemical mechanisms. Although the obtained results suggest that pseudobrookite is not a feasible material to be used alone as feedstock for the electrolytic iron production, it can be considered with other iron oxide materials and/or ores to promote electroreduction.

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Section: Studies Of the Relevant Redox Processes By Cyclic Voltammetrymentioning

confidence: 76%

Section: Structural and Microstructural Features Of The Ceramic Cathodesmentioning

confidence: 79%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Prospects of Using Pseudobrookite as an Iron-Bearing Mineral for the Alkaline Electrolytic Production of Iron

et al. 2022

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Deoxidation Electrolysis of Hematite in Alkaline Solution: Impact of Cell Configuration and Process Parameters on Reduction Efficiency

Fayaz,

Bösing,

La Mantia

et al. 2023

ChemElectroChem

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Recent research is investigating deoxidation electrolysis for eco‐friendly iron extraction. However, many parameters are not fully understood and inconsistencies in reported Faradaic efficiencies pose challenges for finding the most suitable experimental conditions. Thus, we investigated the dependence of hematite reduction efficiency on process parameters and cell configurations. Firstly, we studied the influence of the anode material. The experiments included cyclic voltammetry to identify the redox potentials, electrolysis, and X‐ray diffraction followed by Rietveld refinement to analyze the pellets after electrolysis. In some cases, scanning electron microscopy equipped with energy‐dispersive X‐ray spectroscopy was employed to track the elemental map of the cathode pellets. Nickel/iron alloy, a well‐known oxygen‐evolving electrocatalyst material, clearly outperformed other anode materials, namely graphite, titanium, nickel, and platinum. Subsequent investigations explored the impact of an inert atmosphere and anode‐cathode decoupling on Faradaic efficiency. The findings indicated that the decline in Faradaic efficiency cannot be solely attributed to the hydrogen evolution reaction, but also to other parasitic effects such as carbon cycles. Additionally, we employed energy consumption measurements as a mean of comparing the process against established extractive methodologies. The required energy consumption by electrolysis is up to 46 % lower than that of a blast furnace.

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Application of the distribution of relaxation time method in electrochemical analysis of the air electrodes in the SOFC/SOEC devices: A review

Ghamarinia

Babaei

Zamani

et al. 2023

Chemical Engineering Journal Advances

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Electrochemical reduction of hematite-based ceramics in alkaline medium: Challenges in electrode design

Cited by 14 publications

References 32 publications

Prospects of Using Pseudobrookite as an Iron-Bearing Mineral for the Alkaline Electrolytic Production of Iron

Prospects of Using Pseudobrookite as an Iron-Bearing Mineral for the Alkaline Electrolytic Production of Iron

Deoxidation Electrolysis of Hematite in Alkaline Solution: Impact of Cell Configuration and Process Parameters on Reduction Efficiency

Application of the distribution of relaxation time method in electrochemical analysis of the air electrodes in the SOFC/SOEC devices: A review

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