Search results for "Prussian Blue"
showing 10 items of 57 documents
Metal-to-metal electron transfer and magnetic interactions in a mixed-valence Prussian Blue analogue
2006
Abstract In search of a new Prussian Blue analogue exhibiting fascinating magnetic properties, potassium manganese hexacyanoferrate, K 0.2 Mn 0 . 66 II Mn 1.44 III [ Fe 0.2 II Fe 0.8 III ( CN ) 6 ] O 0.66 ( CH 3 COO ) 1.32 ] , 7.6H2O, has been synthesized. This compound undergoes a paramagnetic to ferrimagnetic transition at 10 K. Temperature and magnetic field-dependent magnetization studies of this compound have revealed different spin alignments below and above 3 K. The nature of possible magnetic interactions between the nearest neighbor magnetic centers has been discussed in order to explore the origin of the observed magnetic interactions. Mossbauer spectroscopic study at different te…
Innovative Combination of Three Alternating Current Relaxation Techniques: Electrical Charge, Mass, and Color Impedance Spectroscopy. Part II: Prussi…
2009
The simultaneous recording of three impedance functions (electrochemical impedance, color, and mass impedance) allows the role of different species to be distinguished easily during electrochemical processes in conducting and electrochromic films. Herein, this technique has been applied to the study of the Prussian blue films at several potentials between the blue form (Prussian blue) and the colorless form (Everitt’s salt). At these potentials, these electrochemical reactions take place by means of exchange of different ions. Thus, the exchange of potassium cations is related to the changes of absorbance at 690 nm, whereas the exchange of protons does not introduce color changes at this wa…
Usefulness of the Instantaneous Mass-charge Ratio for Elucidating the Ions Role in the Stabilization and Dissolution Processes in Prussian Blue Films
2007
The conversion process of 'insoluble' Prussian Blue films into the 'soluble' structure has been followed by the simultaneous measurement of current and mass changes during voltammetric experiments and focusing on the possibilities of the use of the instantaneous mass/electrical charge ratio at each potential. A similar procedure was used for the analysis of the mechanism of reduction of Prussian Blue films to the Everitt's Salt form and to follow the partial dissolution of iron species during the oxidation to the Pussian Yellow form. The possibility of covering Prussian Blue films by Nafion membranes which make difficult the transport of anions through it allows to discern the role of anion…
Magnetic ordering in an (Fe0.2Cr0.8)1.5[Cr(CN)6] Prussian blue analogue studied with synchrotron radiation based spectroscopies
2018
The appearance of magnetic order in the (Fe0.2Cr0.8)1.5[Cr(CN)6]·15H2O Prussian blue analogue at low temperature has been investigated by means of synchrotron radiation-based X-ray absorption spectroscopy and X-ray magnetic circular dichroism. With the help of ligand field multiplet analysis we have been able to identify the oxidation states of the metallic cations present in the sample and their evolution with temperature. Our experiments reveal that the appearance of ferromagnetic order is triggered by the transformation of CrIII cations to CrII high-spin caused by a transfer of electrons from the Fe to the Cr resulting in an increase of the magnetic interactions within the (Cr, Cr) subla…
Electrochemistry of TiO2–iron hexacyanocobaltate composite electrodes
2014
Abstract In this paper we investigate the electrochemical behavior of iron hexacyanocobaltate (FeHCC) in comparison to the cobalt hexacyanoferrate (CoHCF). The best results were achieved on electrochemical synthesized film of FeHCC on the TiO2 modified electrodes. The chemical and physical characterizations confirm the formation of the FeHCC with the classical cubic crystal structure of the Prussian blue analogs, with cell parameter a very close to 10 A, as well as the formation of micro aggregates of TiO2 covered by FeHCC. The synthesis was performed on various substrates such as glassy carbon (GC), graphite foil (GF) and indium tin oxide (ITO) in order to develop new technological applica…
MOKE magnetometry as a probe of surface magnetic impurities in electropolymerized magnetic thin films of the Prussian blue analogue Fe3[Cr(CN)6]2·15 …
2013
A magneto-optical Kerr effect (MOKE) study has been performed on electrodeposited thin films of the Prussian blue analogue Fe3[Cr(CN)6]2·15H2O (1). This study reveals the onset of hysteretic magnetic signals at temperatures above 60 K, in contrast with magnetic susceptibility measurements which indicate a Curie temperature of 23 K for this ferromagnetic film. The origin of this discrepancy is due to the presence of amorphous iron oxide particles that accumulate in the surface of the material. This report illustrates the potential of MOKE magnetometry for the detection of surface chemical impurities that remain elusive using bulk magnetic techniques.
One-stage periodical anodic-cathodic double pulse deposition of nanocomposite materials. Application to Prussian Blue/polypyrrole film coated electro…
2014
Abstract Novel electrochemical method of one-stage deposition of composite films on electrode surface has been proposed. The procedure includes a periodical series of potentiostatic or galvanostatic pulses of alternative polarity imposed at electrode in contact with a mixture of two solute precursors, one of which is able to generate a solid phase under its electrooxidation while another one is transformed into another solid phase under its electroreduction. Parameters of anodic and cathodic pulses (potential or current, pulse duration) may be chosen independently from one another, their relation allows one to vary the relative contents of components in the deposited composite. Thickness of…
Ohmic drop of Prussian-blue/graphite+epoxy electrodes
1999
Abstract Ohmic drop effects on the voltammogram shape of the Prussian-blue⇌Everitt’s salt system have been studied by considering the electroactive film model. As the uncompensated resistance varies, the experimental characteristic curve parameters also varies. A dependence of the voltammograms with the graphite proportion was found related with the ohmic drop due to the composite electrodes. The optimal graphite proportion to obtain a good faradaic-to-charge current ratio was 62% in weight which coincides with the second percolation threshold. The ohmic overpotential, which relates the ohmic drop with the electrochemical magnitudes, is also minimum at this proportion.
The correlation between electrochemical impedance spectra and voltammograms of PB films in aqueous NH4Cl and CsCl
1998
Abstract Voltammetric curves of reduction of Prussian Blue Films to the Everitt’s Salt form and oxidation to the Prussian Yellow form show important differences depending on the supporting electrolyte countercation. The rate of the overall electron-hopping depends on the countercation. Apparent diffusion coefficients are evaluated from impedance spectra at different stabilization potentials. The dependence of the apparent diffusion coefficients on the stabilization potential can help understand the dependence of the voltammograms shape on the countercation nature.
Enhancing the electrocatalytic activity and stability of Prussian blue analogues by increasing their electroactive sites through the introduction of …
2021
Prussian blue analogues (PBAs) have been proven as excellent Earth-abundant electrocatalysts for the oxygen evolution reaction (OER) in acidic, neutral and alkaline media. Further improvements can be achieved by increasing their electrical conductivity, but scarce attention has been paid to quantify the electroactive sites of the electrocatalyst when this enhancement occurs. In this work, we have studied how the chemical design influences the specific density of electroactive sites in different Au-PBA nanostructures. Thus, we have first obtained and fully characterized a variety of monodisperse core@shell hybrid nanoparticles of Au@PBA (PBA of NiIIFeII and CoIIFeII) with different shell siz…