Electrochemical quartz crystal microbalance study on the redox transformations of ruthenium(III) trichloride microcrystals attached to a gold electrode

• Published in: Electrochemistry communications 2004-08, Vol.6 (8), p.805-811
• Main Authors: Inzelt, G, Puskás, Z
• Format: Article
• Language: English
• Subjects: Chemistry; Complex formation; Electrochemical quartz crystal microbalance; Electrochemistry; Exact sciences and technology; General and physical chemistry; Kinetics and mechanism of reactions; Microcrystals; Ruthenium(III) chloride; Solid state voltammetry
• ISSN: 1388-2481; 1873-1902
• DOI: 10.1016/j.elecom.2004.05.019

Ruthenium(III) trichloride solid crystals have been mechanically attached to gold surfaces and studied by cyclic electrochemical quartz crystal microbalance measurements in the presence of aqueous solutions containing 0.1 mol dm −3 HCl + x mol dm −3 M +Cl −, where M +=H +, Li +, Na +, K +, Rb +, Cs +. The first cycle differed from the subsequent ones not only for the virgin layer, but also when the electrode was used again after storing it in dry state. The RuCl 3 and the complexes formed during the electrochemical transformations show two reduction and two reoxidation waves, in some cases (during the first break-in and in the presence of potassium ions) two peaks appear in the course of the second oxidation process. The peak potentials are shifted into the direction of more positive potentials with increasing electrolyte concentrations and in the series of H +, Li +, Na +, Rb +, K +, Cs +. The mass change was reversible, during reduction mass decrease, while during oxidation mass increase occurred in two distinct steps. It was concluded that during reduction the incorporation of M + ions takes place, while simultaneously H 2O molecules leave the surface layer. The opposite transport of ions and solvent molecules occurs during oxidation. A reaction scheme is proposed in which H +Ru 3 IIICl 10(H 2O) 8 · xH 2O type complexes are formed from RuCl 3 · xH 2O during the break-in cycle. The two reduction/reoxidation waves are related to the redox transformations of two Ru(III) to Ru(II) sites while the composition of the polynuclear complexes and the structure of microcrystals change.