Diminished Electron Transfer Kinetics for [Ru(NH3)6]3+/2+, [α-SiW12O40]4–/5–, and [α-SiW12O40]5–/6– Processes at Boron-Doped Diamond Electrodes

Abstract

Heterogeneous electron transfer rate constants (k0 values) at a boron-doped diamond (BDD) electrode (10–2 cm s–1 range) that are more than an order of magnitude smaller than found at metal or glassy carbon (GC) electrodes (≥2.0 cm s–1) are reported for the outer-sphere [Ru(NH3)6]3+/2+, [α-SiW12O40]4–/5–, and [α-SiW12O40]5–/6– redox couples in aqueous electrolyte media. The k0 values and other parameters relevant to electrode kinetics were derived from analysis of the higher-order harmonic components available in Fourier transformed large amplitude alternating current voltammetry at BDD, GC, and platinum (Pt) or gold (Au) electrodes for the reduction of highly positively charged [Ru(NH3)6]3+ and highly negatively charged Keggin-type silicon tungstate ([α-SiW12O40]4– and [α-SiW12O40]5–). The slower electron transfer kinetics at the BDD electrode, relative to the other electrode materials, are discussed in terms of the double layer, density of states, and other factors.