Thermal analysis of some cyano compounds

Marco, Domenico De; Marchese, A.; Migliardo, P.; Bellomo, Athos

doi:10.1007/bf01913779

Cited by 13 publications

(11 citation statements)

References 15 publications

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“…Note that no signs of hydrogen cyanide (m/z = 27) evolution were observed. The evolution of (CN) 2 is known to occur during thermal decomposition of certain metal hexacyanoferrates in air and under inert atmosphere, [65,66] while during battery operation, to the best of our knowledge, it is the first report of this kind of degradation of PBA cathodes. The irreversibility of such side reaction is evident at voltages above 4.1 V from the differential capacity plots in Figure 7b (marked by an arrow).…”

Section: (4 Of 10)mentioning

confidence: 90%

High‐Entropy Metal–Organic Frameworks for Highly Reversible Sodium Storage

et al. 2021

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Prussian blue analogues (PBAs) are reported to be efficient sodium storage materials because of the unique advantages of their metal–organic framework structure. However, the issues of low specific capacity and poor reversibility, caused by phase transitions during charge/discharge cycling, have thus far limited the applicability of these materials. Herein, a new approach is presented to substantially improve the electrochemical properties of PBAs by introducing high entropy into the crystal structure. To achieve this, five different metal species are introduced, sharing the same nitrogen‐coordinated site, thereby increasing the configurational entropy of the system beyond 1.5R. By careful selection of the elements, high‐entropy PBA (HE‐PBA) presents a quasi‐zero‐strain reaction mechanism, resulting in increased cycling stability and rate capability. The key to such improvement lies in the high entropy and associated effects as well as the presence of several active redox centers. The gassing behavior of PBAs is also reported. Evolution of dimeric cyanogen due to oxidation of the cyanide ligands is detected, which can be attributed to the structural degradation of HE‐PBA during battery operation. By optimizing the electrochemical window, a Coulombic efficiency of nearly 100% is retained after cycling for more than 3000 cycles.

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Section: (4 Of 10)mentioning

confidence: 90%

High‐Entropy Metal–Organic Frameworks for Highly Reversible Sodium Storage

et al. 2021

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“…Those compounds which contain alkali metal ions (for example, NaCN, potassium ferroand ferricyanide, sodium ferro-and mixed potassium-lanthanide ferrocyanide) giv, e rise to the formation of cyanate [3,4], while this species is not formed ) It can be assumed that the presence of an alkali metal ion is a necessary, but not sufficient condition for the formation.of NCO-. Those compounds which contain alkali metal ions (for example, NaCN, potassium ferroand ferricyanide, sodium ferro-and mixed potassium-lanthanide ferrocyanide) giv, e rise to the formation of cyanate [3,4], while this species is not formed ) It can be assumed that the presence of an alkali metal ion is a necessary, but not sufficient condition for the formation.of NCO-.…”

Section: Discussionmentioning

confidence: 99%

“…The heating temperatures were selected on the basis of the thermal analysis curves, and the isothermal heating period on the basis of preliminary experiments [3,4]. At each temperature, the sample was maintained under isothermal conditions for 5 minutes.…”

Section: Infrared Spectramentioning

confidence: 99%

Thermal analysis of some cyano compounds

Marco

1989

Journal of Thermal Analysis

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The thermal behaviour of the cyano compounds NaCN, K,,Fe(CN)6.3H20, KaFe(CN)6 , K3Co(CN)6 and K2Hg(CN)4 has been investigated by using conventional thermal analysis techniques and infrared spectroscopy. The results indicate the absence of "decomplexing'" reactions for all the complexes, and "internal" redox reactions for the compounds KaFe(CN)6, K3Co(CN) 6 and K2Hg(CN)4. In all the investigated cases, the formation of cyanate and carbonate is demonstrated.In aqueous solution the cyanide ion binds to transition metal ions to form complexes of high thermodynamic stability [1][2][3]. Some of them are inert too and they readily give rise to heteropolynuclear complexes with variable stoichiometry, depending on the experimental conditions of formation [4--6]. Compounds such as Ag4Fe(CN) 6, KAg3Fe(CN)6 and Hg2Fe(CN)6 (white) alter swiftly in air, while others, such as K2Zna[Fe(CN)6]2 or KLaFe(CN)6 (white), are stable for a long time. Very different behaviour is evident as regards "internal" and/or "external" reactions, depending on the nature both of the central ion of the cyano complex (inside the anion moiety of the compound) and of the counter cations [7]. On the whole, the presence of highly polarizing cations favours the oxidative decomposition of cyanide compounds [9].Seifer [10][11][12][13][14][15] has investigated the thermal behaviour of hexacyanoferrates(II) in an inert atmosphere by using compounds where the cation moiety was constitued by "free" or at most hydrated ions. The results showed a very complicated set of endo-and excthermic effects, but the interpretation given by Seifer allows one to outline a scheme of behaviour.* Supported by the Italian MPI. Presented at "Journ6es

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“….). Because closely spread equilibrium isotherms are experimentally observed both for different series of reactions in the same solvent (8,(10)(11)(12)(13) or for the same series of reactions in different but similar solvents (water, methanol, ethanol) (14)(15)(16) it can be concluded that in the cases investigated the values of τ are mainly determined by the nature and the role of the solvent medium. (iv) The solvent molecules involved in the complex formation reactions appear to be the main factor that determines the relative position of the reactions in the respective trend.…”

Section: Discussionmentioning

confidence: 95%

“…The phenomenon occurs in the series analyzed in the present work, in the series of complexing reaction of Ag(I), (14)(15)(16) of Hg(II) (13) and in several series of complexing reactions with rare earth metal ions. (10,11) It can be concluded that, in the successive stepwise complex formation, the system gains and loses stiffness in an alternating way corresponding to the alternating release of the solvent molecules from the coordination spheres of the reactants.…”

Section: Discussionmentioning

confidence: 96%