Structural Analysis of K₄Fe(CN)₆·3H₂O, K₃Fe(CN)₆ and Prussian Blue

Abstract

XRD and XAS were used to characterize the bulk structure, while XPS was used to characterize the surface structure, of commercially obtained nominally K4Fe(CN)6·3H2O, K3Fe(CN)6 and our synthesized Prussian Blue (PB) material. K4Fe(CN)6·3H2O was found to consist of a fully hydrated phase, which crystallizes in the monoclinic form and a less hydrated or anhydrous phase which crystallizes in the orthorhombic form. K3Fe(CN)6 was found to consist of the well-established orthorhombic form rather than the monoclinic form. The structure of our synthesized Prussian Blue (PB) was found to be consistent with that reported for (KOH)0.7Fe(III)1.33Fe(II)(CN)6·4.0H2O which crystallizes in the cubic form. XPS and XAS confirmed the presence of ferrous Fe(II) at the surface and bulk levels in K4Fe(CN)6·xH2O. However, XPS revealed the presence of Fe(II) (∼30%) and Fe(III) (∼70%) in the surface region of K3Fe(CN)6 while XAS confirmed the presence of mostly Fe(III) at the bulk level. Both XPS and XANES confirmed the presence of Fe(II) and Fe(III) in the surface and bulk regions of PB. This ex situ XAS study will be used to support the analysis of an in situ XAS data collected on a PB containing supercapacitor to understand the mechanistic origin of pseudocapacitance in these devices.

Electrochemical and In Situ Spectroscopic Study of the Effect of Prussian Blue as a Mediator in a Solid-State Supercapacitor

“…Based on our recently reported XRD results, 28 the crystal structure of our synthesized PB used in this investigation was found to be consistent with the cubic lattice with space group Fm m 3 ¯and unit cell dimension 10.178 Å, which was reported for a material with composition (KOH) 0.7 Fe(III) 4/3 Fe(II)(CN) 6 •4H 2 O. However, incorporating our composition results derived on the basis of surface sensitive XPS and bulk sensitive EDS, we believe the true composition of our synthesized PB may be closer to (KOH) x Fe(III) 4/3 Fe(II)(CN) 6 •zH 2 O where x is < 0.7 and z is < 4.0.…”

“…Detailed ex situ spectroscopic results including XPS, EDAX results and XAS are presented in Ref. 28.…”

“…The data collection parameters for the ex situ data of PB loaded in the boron nitride pellet and the pristine electrode were reported in an earlier publication. 28 Analysis of XAS data was carried out using the IFEFFIT suite of programs. 29,30 For ex situ XAS, samples with PB were prepared in two different ways to explore the effect of electrode synthesis on chemical state and structure.…”

Ultrasensitive Detection of Carcinoembryonic Antigen by Chitosan/Polythiophene/CdTe Electrochemical Biosensor

“…Two strong peaks at 721.5 and 708.7 eV are comparable to those of K 4 Fe(CN) 6 , indicating that there is no change of electrolyte during the oxidation process. 55,56 When the above experiment is repeated with CS/PTh electrode instead, an Fe 2p 3/2 peak at 710.6 eV and an Fe 2p 1/2 peak at 724.1 eV corresponding to the binding energy of Fe (III+) are observed because Fe (II+) is oxidized to Fe (III+) after the electrochemical reaction (Figure 5D). 57 The results of XPS analysis are consistent with the results of IR spectroelectrochemistry.…”

Tailored Persistent Radical‐containing Heterotrimetal‐Organic Framework for Boosting Efficiency of Visible/NIR Light‐driven Photocatalytic CO2 Reduction

“…The XPS results in Figure 3e show a new O 1s core-level peak at binding energy 532.9 eV for IHEP-15, which is attributed to CO 2 adsorbed at radical sites. [74,75]…”