Oxidation of chukanovite (Fe 2 (OH) 2 CO 3 ): Influence of the concentration ratios of reactants

Azoulay, I.; Rémazeilles, C.; Refait, Philippe

doi:10.1016/j.corsci.2015.06.002

Cited by 11 publications

(4 citation statements)

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“…This is demonstrated by the XRD patterns of the sample obtained at the ratio of 2:1 and with only Fe 2+ added showing characteristic peaks of chukanovite (Fe 2 (OH) 2 CO 3 , JCPDS 33-0650) (Figure S8). , The higher content of Fe to be oxidized to FeOOH rather than Fe 2 O 3 at higher ratios of Ni 2+ to Fe 2+ is probably due to the larger work function of Ni than that of Fe promoting the oxidation of Fe to FeOOH, which has a higher binding energy of Fe than Fe 2 O 3 . ,, The formation of large and severely aggregated particles at the low ratios of Ni 2+ to Fe 2+ is very likely caused by the fast reaction of Fe 2+ with OH – and CO 3 2– leading to their preferential nucleation in solution (Figure D,F). , …”

Section: Resultsmentioning

confidence: 99%

Tannic Acid-Mediated In Situ Controlled Assembly of NiFe Alloy Nanoparticles on Pristine Graphene as a Superior Oxygen Evolution Catalyst

Zhao

Yuan

et al. 2020

ACS Appl. Energy Mater.

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Controlled assembly of small and highly dispersed earth-abundant transition metal-based oxygen evolution reaction (OER) catalysts on pristine graphene could greatly boost the OER efficiency while significantly reducing the cost, but this presents great challenges. Pristine graphene (rather than reduced graphene oxide or graphene with a damaged electronic structure) supported NiFe alloy nanoparticles (NPs) have been synthesized for the first time via tannic acid (TA)-mediated in situ controlled assembly, in which TA not only noncovalently modifies the graphene to strongly coordinate with Ni 2+ and Fe 2+ but also in situ reduces these metal ions to alloy NPs. The chemical composition of these alloy NPs can be tailored via changing the ratio of Ni 2+ and Fe 2+ in the reaction. These nanohybrids show ultrahigh and tunable OER catalytic activities. The optimum one obtained using the ratio of 9:1 achieves 10 mA cm −2 at an overpotential of 246 mV and shows a Tafel slope of 46 mV dec −1 , both of which are lower than those of most reported OER catalysts, including state-of-the-art Ru-and Ir-based ones. In addition, this catalyst exhibits little change of the overpotential after 20 h of chronopotentiometric measurement (from 246 to 258 mV at 10 mA cm −2 ) and negligible current loss after 1000 CV cycles (from 123.3 to 133.4 mA cm −2 at 1.54 V). The superior catalytic activity and durability are ascribed to the in situ assembled small, highly dispersed, and highly conductive NiFe alloy NPs on pristine graphene significantly facilitating the electron transfer and increasing the electrochemically accessible active sites, the doped FeOOH remarkably promoting the intrinsic activity of Ni(OH) 2 on the surface of these alloy NPs, and the robust in situ growth greatly enhancing the durability during the OER testing. This work provides a green, facile, and economical strategy to controllably fabricate low-cost and high-performance OER catalysts and also sheds light on the performance enhancement mechanism from tunable OER catalytic activity.

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Section: Resultsmentioning

confidence: 99%

Tannic Acid-Mediated In Situ Controlled Assembly of NiFe Alloy Nanoparticles on Pristine Graphene as a Superior Oxygen Evolution Catalyst

Zhao

Yuan

et al. 2020

ACS Appl. Energy Mater.

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“…8,9 In our earlier work, we showed the formation of siderite only, or of siderite and chukanovite with ratio dependent on the solution pH. [10][11][12] The formation of chukanovite comes into focus because Azoulay et al 13,14 showed that the oxidation of chukanovite in solutions containing Fe(II) and CO 3 2− led directly to FeOOH, without the intermediate formation of Fe 6 (OH) 12 CO 3 : that compound was formed by the oxidation of Fe(OH) 2 . They also noted the formation of an oxidized chukanovite, Fe II 2-x Fe III x (OH) 2-x O x CO 3 (x < 0.25) without alteration of the crystal structure.…”

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confidence: 93%

Effects of Oxygen on Scale Formation in CO₂Corrosion of Steel in Hot Brine: In Situ Synchrotron X-ray Diffraction Study of Anodic Products

Ingham¹,

Ko²,

Shaw³

et al. 2018

J. Electrochem. Soc.

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The effect of low concentrations of oxygen on the anodic dissolution of carbon steel in CO 2 -saturated aqueous NaCl at 80 • C is simply to change the dissolution product from colloidal amorphous material assumed to be amorphous ferrous carbonate to a crystalline carbonate green rust, Fe 6 (OH) 12 CO 3 , which forms rapidly. This material is deposited from solution and does not inhibit the dissolution. Corrosion is limited by the nucleation onto the surface and growth of a crystalline scale of siderite (FeCO 3 ), as in the absence of oxygen. The effects of oxygen and of solution flow can be understood in terms of effects on supersaturation for carbonate crystallization, and on the effect on the surface pH, caused by the precipitation of carbonate green rust. The formation of crystalline chukanovite (Fe 2 (OH) 2 CO 3 ) is strongly affected in the presence of trace oxygen, both by flow and electrode potential, effects which are consistent with lower supersaturation and higher surface pH caused by green rust precipitation. In the presence of trace oxygen, FeOOH and Fe 3 O 4 could be detected in small amounts, and are assumed to form as a consequence of the oxidation of chukanovite.

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“…Thermodynamic calculations postulate that goethite is the oxidation product of the metastable chukanovite (Fe 2 (OH) 2 CO 3 ), which has also been implicated in the formation of iron carbonate . In fact, chukanovite oxidation to goethite has been suggested to proceed through an Fe(III)-containing intermediate green rust (Fe 2 II – x Fe III x (OH) 2– x O x CO 3 ). , Such a green product was observed prior to goethite formation (Figure ). Hematite, however, is not generated from chukanovite, rather one possible precursor is free Fe 2+ in solution.…”

Section: Resultsmentioning

confidence: 99%

“…24 In fact, chukanovite oxidation to goethite has been suggested to proceed through an Fe(III)-containing intermediate green rust (Fe 2 II −x Fe III x (OH) 2−x O x CO 3 ). 30,45 Such a green product was observed prior to goethite formation (Figure 11). Hematite, however, is not generated from chukanovite, rather one possible precursor is free Fe 2+ in solution.…”

Section: Comentioning

confidence: 95%

Understanding the Role of NaCl Concentration on the Corrosion of Carbon Steel and FeCO₃ Formation in CO₂-Containing Electrolytes

Alsalem

Camilla

Ryan

et al. 2021

Ind. Eng. Chem. Res.

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The formation of FeCO3 was studied as a function of NaCl solutions (1 and 3% w/v), saturated with CO2 (pH ∼ 6) at 80 °C. Individual crystal growth and properties, the formation of films, and the corrosion resistance of C1018 carbon steel were assessed. Immersion experiments were conducted from 6 to 168 h. Monitoring ex situ used the substrate weight loss method with dissolved iron concentration measurements (from bulk solution) by inductively coupled plasma-mass spectroscopy (ICP-MS). After exposure, scanning electron microscope (SEM), X-ray diffraction (XRD), and Raman spectroscopy were employed to understand FeCO3 amorphous/crystalline nature and surface composition. Complementary electrochemical measurements [open circuit potential (OCP), potentiodynamic polarization] were conducted to understand the impact of NaCl on cathodic and anodic processes. The role of NaCl was significantly more nuanced than the general corrosion rates might suggest (initially decreasing with increasing NaCl concentration). The induction time and nature of the FeCO3 formed are strongly influenced by the NaCl concentration. First, increasing NaCl concentration retarded the nucleation of FeCO3 crystals. Second, this same increase also induced crystal ripening and habit modification. Collectively, this leads to a porous, less protective layer of FeCO3.

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Oxidation of chukanovite (Fe 2 (OH) 2 CO 3 ): Influence of the concentration ratios of reactants

Cited by 11 publications

References 36 publications

Tannic Acid-Mediated In Situ Controlled Assembly of NiFe Alloy Nanoparticles on Pristine Graphene as a Superior Oxygen Evolution Catalyst

Tannic Acid-Mediated In Situ Controlled Assembly of NiFe Alloy Nanoparticles on Pristine Graphene as a Superior Oxygen Evolution Catalyst

Effects of Oxygen on Scale Formation in CO₂Corrosion of Steel in Hot Brine: In Situ Synchrotron X-ray Diffraction Study of Anodic Products

Understanding the Role of NaCl Concentration on the Corrosion of Carbon Steel and FeCO₃ Formation in CO₂-Containing Electrolytes

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Oxidation of chukanovite (Fe 2 (OH) 2 CO 3 ): Influence of the concentration ratios of reactants

Cited by 11 publications

References 36 publications

Tannic Acid-Mediated In Situ Controlled Assembly of NiFe Alloy Nanoparticles on Pristine Graphene as a Superior Oxygen Evolution Catalyst

Tannic Acid-Mediated In Situ Controlled Assembly of NiFe Alloy Nanoparticles on Pristine Graphene as a Superior Oxygen Evolution Catalyst

Effects of Oxygen on Scale Formation in CO2Corrosion of Steel in Hot Brine: In Situ Synchrotron X-ray Diffraction Study of Anodic Products

Understanding the Role of NaCl Concentration on the Corrosion of Carbon Steel and FeCO3 Formation in CO2-Containing Electrolytes

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Effects of Oxygen on Scale Formation in CO₂Corrosion of Steel in Hot Brine: In Situ Synchrotron X-ray Diffraction Study of Anodic Products

Understanding the Role of NaCl Concentration on the Corrosion of Carbon Steel and FeCO₃ Formation in CO₂-Containing Electrolytes