Hello,
since I work in the field of electrochemistry I am trying different metal ferricyanide complexes as cathodes in batteries. The thing that confuses me is the reaction behavior, so lets say we got pure CuHCF, which should have the composition Cu2[Fe(CN)6] and if it reduces in a lithium electrochemical cell it should then look like Li2Cu[Fe(CN)6] or depending on the oxidation state LiCu[Fe(CN)6] which makes it an very attr material for cathodes. But how would it react with other metal anodes, for example Al Anode? My hypothesis is that it doesn’t substitute the cooper (so no Al[Fe(CN)6] or Al4[Fe(CN)6] formation) but rather forms Al{Cu[Fe(CN)6]}3 or Al2{Cu[Fe(CN)6]}3 because it will only substitute if the other metal salt was a higher lewis acid compound, so theoretically it should substitute if the Al3+ salt is anaqueous but not if it is hydrated because then the compound won‘t be per definition very strong lewis-acids. So how do I know which salts will substitute my copper hexacyanoferrate and which not? So according to my hypothesis substitution should only take place if the metal has following properties: 1.) it has to be a strong lewis acid 3.) its valence electrons should be as high as possible and the atomic radius as low as possible right?
Help is appreciated, because I am very confused right now
HCF commonly reffers to M[Fe(CN)6] so CuHCF is CuFe(CN)6 and monovalent cations are stored in a A site in the middle of the unit cell. Aluminum has been used as a substrate for NiHCF and shouldn't substitute. The Cu is coordinated with nitrogen. Mn, Ni, Cu, Co are all common metals in HCF structures and I have been Na, K, Li and NH4 as cations.
There is a lot of literature out there on this class of materials but here are a few
iScience 3, 110–133, May 25, 2018
Chem. Commun ., 2012, 48, 6544–6546
Chem. Mater. 2003, 15, 3046-3062
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