| 1. |
- Renman, Viktor, et al.
(författare)
-
Structural-electrochemical relations in the aqueous copper hexacyanoferrate-zinc system examined by synchrotron X-ray diffraction
- 2017
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 369, s. 146-153
-
Tidskriftsartikel (refereegranskat)abstract
- The storage process of Zn2+ in the Prussian blue analogue (PBA) copper hexacyanoferrate (Cu[Fe(CN)(6)](2/3)-nH(2) O-CuHCF) framework structure in a context of rechargeable aqueous batteries is examined by means of in operando synchrotron X-ray diffraction. Via sequential unit-cell parameter refinements of time-resolved diffraction data, it is revealed that the step-profile of the cell output voltage curves during repeated electrochemical insertion and removal of Zn2+ in the CuHCF host structure is associated with a non-linear contraction and expansion of the unit-cell in the range 0.36 < x < 1.32 for Znx/3Cu[Fe(CN)(6)](2/3)-nH(2)O. For a high insertion cation content there is no apparent change in the unit-cell contraction. Furthermore, a structural analysis with respect to the occupancies of possible Zn2+ sites suggests that the Fe(CN)(6) vacancies within the CuHCF framework play an important role in the structural-electrochemical behavior of this particular system. More specifically, it is observed that Zn2+ swaps position during electrochemical cycling, hopping between cavity sites to vacant ferricyanide sites.
|
|
| 2. |
- Wardecki, Dariusz, et al.
(författare)
-
Neutron Diffraction and EXAFS Studies of K2x/3Cu[Fe(CN)(6)](2/3)center dot nH(2)O
- 2017
-
Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 17:3, s. 1285-1292
-
Tidskriftsartikel (refereegranskat)abstract
- The crystal structure of copper hexacyanoferrate (CuHCF), K2x/3Cu[Fe-(CN)(6)](2/3)center dot nH(2)O, with nominal compositions x = 0.0 and x = 1.0 was studied by neutron powder diffraction (NPD) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The compound crystallizes in space group Fm (3) over barm, with a = 10.1036(11) angstrom and a = 10.0588(5) angstrom for x = 0.0 and x = 1.0, respectively. Difference Fourier maps for x = 0.0 show that the coordinated water molecules are positioned at a site 1921 close to vacant N positions in the -Fe-C-N-Cu- framework, while additional zeolitic water molecules are distributed over three sites (8c, 32f, and 48g) in the -Fe-C-N-Cu- framework cavities. The refined water content for x = 0.0 is 16.8(8) per unit cell, in agreement with the ideal 16 (n = 4). For x = 1.0, the refinement suggests that 2.6 K atoms per unit cell (x = 0.98) are distributed only over the sites 8c and 32f in the cavities, and 13.9(7) water per unit cell are distributed over all the four positions. The EXAFS data for Fe, Cu, and K K-edges are in agreement with the NPD data, supporting a structure model with a linear -Fe-C-N-Cu- framework and K+ ions in the cavities.
|
|
| 3. |
- Åkerblom, Ida E., et al.
(författare)
-
A thermogravimetric study of thermal dehydration of copper hexacyanoferrate by means of model-free kinetic analysis
- 2017
-
Ingår i: Journal of thermal analysis and calorimetry (Print). - : Springer Science and Business Media LLC. - 1388-6150 .- 1588-2926. ; 129:2, s. 721-731
-
Tidskriftsartikel (refereegranskat)abstract
- The kinetics of thermal dehydration of K2x/3Cu[Fe(CN)6]2/3·nH2O was studied using thermogravimetry for x = 0.0 and 1.0. Data from both non-isothermal and isothermal measurements was used for model-free kinetic analysis by the Friedman and KAS methods. The water content was determined to be n = 2.9 – 3.9, with an additional ~10% of water, likely surface adsorbed, that leaves very fast when samples are exposed to a dry atmosphere. The determined activation energies are 19 kJ (mol H2O)-1 for x = 0.0 and 16 kJ (mol H2O)-1 for x = 1.0. The dehydration is adequately described as a diffusion controlled single step reaction following the D3 Jander model. The determined dehydration enthalpy is, 11 kJ (mol H2O)-1 for x = 0.0 and 27 kJ (mol H2O)-1 for x = 1.0, relative to that of water. The increase with increasing x is evidence for that the H2O molecules form bonds to the incorporated K+ ions.
|
|
