Organic redox probes for the key oxidation states in mixed valence ruthenium oxide/cyanometallate (ruthenium Prussian blue analogue) catalysts

The electrochemical redox behavior of the polynuclear mixed valence ruthenium oxide cyanometallate complexes (mvRuOx-MCN, M=Fe, Cr, Ni, Cu, Ru and Pt) have been systematically studied in this report by using three redox sensitive organic probes of glucose, ethanol and formaldehyde. The results were interpreted by the well-established ruthenium oxide and Prussian blue chemistry. The mvRuOx-MCN, under the category of Ru-based Prussian blue analogue, was found to possess superior electrocatalytic activity than either ruthenium oxide or Prussian blue in acidic mediums. The electrogenerated oxy/hydroxy-Ru-VII state (at + 1.1 V vs. Ag/AgCl) was unusually stabilized in the mvRuOx-MCN matrix without any disproportion reaction in acidic environments. In contrast to those of earlier studies, possible structure in terms of the -Ru-III/II-NC-M-and -Ru-III/II-O-Ru-VII/VI-sites was proposed here. Enzyme-less analytical detection of glucose in acidic conditions was first time demonstrated with sensitivity comparable to that of ruthenium oxide-based electrodes in alkaline solutions.