Electrochemical nucleation and growth of black and white chromium deposits onto stainless steel surfaces

Aguilar-Sánchez, M.; Palomar-Pardavé, M.; Romero-Romo, M.; Ramı́rez-Silva, Maria Teresa; Barrera, Enrique; Scharifker, B.R.

doi:10.1016/j.jelechem.2010.06.012

Cited by 20 publications

(11 citation statements)

References 25 publications

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“…Since the EDX analysis extends deep in the sample depending on the electron acceleration (kV), the amount of substrate detected can be used to compare the thickness of two different layers. Table 1 shows that the amount of Ti detected is much higher for the surface No clear X-ray diffraction patterns were obtained for the deposits, which is in line with previous findings [26,38].…”

Section: Cr 2 O 3 and Cr(oh)supporting

confidence: 89%

Study of Hypochlorite Reduction Related to the Sodium Chlorate Process

et al. 2016

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Reduction of hypochlorite is the most important side reaction in the sodium chlorate reactor leading to high energy losses. Today chromate is added to the reactor solution to minimize the hypochlorite reduction but a replacement is necessary due to health and environmental risks with chromate. In order to understand the effect of different substrates on the hypochlorite reduction, α-FeOOH, γ-FeOOH, Cr 2 O 3 and CrOH 3 were electrodeposited on titanium and subjected to electrochemical investigations. These substances are commonly found on cathodes in the chlorate process and can serve as model substances for the experimental investigation. The mechanism of hypochlorite reduction was also studied using DFT calculations in which the reaction at Fe(III) and Cr(III) surface sites were considered in order to single out the electrocatalytic properties. The experimental results clearly demonstrated that the chromium films completely block the reduction of hypochlorite, while for the iron oxyhydroxides the process can readily occur. Since the electrocatalytic properties per se were shown by the DFT calculations to be very similar for Fe(III) and Cr(III) sites in the oxide matrix, other explanations for the blocking ability of chromium films are addressed and discussed in the context of surface charging, reduction of anions and conduction in the deposited films. The main conclusion is that the combined effect of electronic properties and reduction of negatively charged ions can explain the reduction kinetics of hypochlorite and the effect of chromate in the chlorate process.

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Section: Cr 2 O 3 and Cr(oh)supporting

confidence: 89%

Study of Hypochlorite Reduction Related to the Sodium Chlorate Process

et al. 2016

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“…XPS has thrown some light towards characterizing this type of films [29,32,39,40], showing either a pure Cr 2 O 3 phase [29,39], a mixture of Cr 2 O 3 and Cr(OH) 3 [40], or a much more complex matrix of different Cr(III) oxyhydroxides [32]. The XPS investigation made in the present work (Fig.…”

Section: Surface Characterizationmentioning

confidence: 70%

“…It is known that the electrodeposition of so-called black chromium yields amorphous Cr(III) oxide films/deposits [29,32,39], whose actual composition is difficult to determine [32]. XPS has thrown some light towards characterizing this type of films [29,32,39,40], showing either a pure Cr 2 O 3 phase [29,39], a mixture of Cr 2 O 3 and Cr(OH) 3 [40], or a much more complex matrix of different Cr(III) oxyhydroxides [32].…”

Section: Surface Characterizationmentioning

confidence: 99%

Electrochemical Investigation of the Hydrogen Evolution Reaction on Electrodeposited Films of Cr(OH)3 and Cr2O3 in Mild Alkaline Solutions

et al. 2017

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The hydrogen evolution reaction (HER) from water reduction is the main cathodic reaction in the sodium chlorate process. The reaction typically takes place on electrodes covered with a Cr(III) oxide-like film formed in situ by reduction of sodium dichromate in order to avoid reduction of hypochlorite and thereby increase the selectivity for the HER. However, the chemical structure of the Cr(III) oxide-like film is still under debate. In the present work, the kinetics of the HER were studied using titanium electrodes covered with electrodeposited Cr(OH) 3 or Cr 2 O 3 , which were characterized by means of scanning electron microscopy (SEM), energydispersive x-ray spectroscopy (EDX), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. A clear difference in the morphology of the deposited surfaces was obtained, and the structure could be revealed with Raman spectroscopy. The kinetics for the HER were investigated using potentiodynamic and potentiostatic techniques. The results show that the first electron transfer is rate limiting and that the activity decreases in the order Cr 2 O 3 @Ti > bare Ti > Cr(OH) 3 @Ti. The low activity obtained for Cr(OH) 3 @Ti is discussed in terms of the involvement of structural water in the HER and the slow ligand exchange rate for water in Cr(III) complexes, while the high activity obtained for Cr 2 O 3 @Ti is rationalized by a surface area effect in combination with reduction of surface water and water in solution.

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“…[] X‐ray photoelectron spectroscopy (XPS), another powerful technique for compositional characterization, has been employed to identify oxygenated Cr(III) species, as powders or films. [] However, the drawback of using XPS is that some peaks superpose at determined intervals of binding energies for Cr(OH) 3 and Cr 2 O 3 ,[] whereby a clear distinction between the two species is not feasible. As an alternative to FTIR and XPS, Raman spectroscopy has shown to be a suitable and important technique to characterize Cr 2 O 3 ,[] which in the crystalline form presents several distinct peaks.…”

Section: Introductionmentioning

confidence: 99%

A micro‐Raman spectroscopic study of Cr(OH)₃ and Cr₂O₃ nanoparticles obtained by the hydrothermal method

Gomes

Yaghini

Martinelli

et al. 2017

J Raman Spectroscopy

106

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Cr2O3 nanoparticles, widely used in the industry, can be obtained by calcination of the nanoparticles synthesized via the hydrothermal method. The chemical nature and the morphology of as‐prepared and calcined nanoparticles are investigated by scanning electron microscopy, X‐ray diffraction and Raman spectroscopy. Our results indicate that the as‐prepared nanoparticles mainly consist of amorphous and hydrated Cr(OH)3, with only minor amounts of Cr2O3. By contrast, and as already known before, calcined nanoparticles consist of Cr2O3. We also demonstrate the effect of inappropriately chosen experimental conditions, because the use of laser intensities above 0.7 mW during the Raman experiments causes a local heating and thus induces the transformation of Cr(OH)3 into Cr2O3. The correlation between the laser power and a local heating is further corroborated by thermogravimetric analyses, which show that upon increased temperature, Cr(OH)3 first dehydrates and then partially condensates to the intermediate CrO(OH) form, to finally attain the crystalline form of Cr2O3 at about 409 °C. Copyright © 2017 John Wiley & Sons, Ltd.

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Electrochemical nucleation and growth of black and white chromium deposits onto stainless steel surfaces

Cited by 20 publications

References 25 publications

Study of Hypochlorite Reduction Related to the Sodium Chlorate Process

Study of Hypochlorite Reduction Related to the Sodium Chlorate Process

Electrochemical Investigation of the Hydrogen Evolution Reaction on Electrodeposited Films of Cr(OH)3 and Cr2O3 in Mild Alkaline Solutions

A micro‐Raman spectroscopic study of Cr(OH)₃ and Cr₂O₃ nanoparticles obtained by the hydrothermal method

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Electrochemical nucleation and growth of black and white chromium deposits onto stainless steel surfaces

Cited by 20 publications

References 25 publications

Study of Hypochlorite Reduction Related to the Sodium Chlorate Process

Study of Hypochlorite Reduction Related to the Sodium Chlorate Process

Electrochemical Investigation of the Hydrogen Evolution Reaction on Electrodeposited Films of Cr(OH)3 and Cr2O3 in Mild Alkaline Solutions

A micro‐Raman spectroscopic study of Cr(OH)3 and Cr2O3 nanoparticles obtained by the hydrothermal method

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A micro‐Raman spectroscopic study of Cr(OH)₃ and Cr₂O₃ nanoparticles obtained by the hydrothermal method