Hybrid metal cyanometallates - Electrochemical charging and spectrochemical identity of heteronuclear nickel/cobalt hexacyanoferrate

Hybrid metal nickel/cobalt hexacyanoferrate (Ni/CoHCNFe) has been prepared in the form of thin films on electrode surfaces and as bulk precipitates (p owders). This heteronuclear metal hexacyanoferrate cannot be considered a s imple mixture of hexacyano-ferrates of nickel and cobalt, and it shows diff erent voltammetric and electrochromic characteristics in comparison to the respective single-metal hexacyanoferrates. On the basis of X-ray absorption , elemental analysis, and comparative voltammetric measurements, the follow ing approximate formulas, (K2Ni0.5Co0.5II)-Co-II[Fe-II(CN)](6) and (KNi0.5C o0.5II)-Co-II[Fe-III(CN)(6)], have been proposed for the predominant reduce d and oxidized forms of hybrid Ni/CoHCNFe. The results are consistent with the existence of linear units -Fe-CN-Co-NC-Fe-CN-Ni- in the structure. Hybr id nickel/cobalt hexacyanoferrate film has unique electrochromic properties , and it shows long-term stability and promising charge storage/transport c apabilities during voltammetric potential cycling. (C) 1999 The Electrochem ical Society. S0013-4651(98)12-008-4. All rights reserved.