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

Heterogeneous electron transfer rate constants (k(0) 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+), [alpha-SiW12O40](4-/5-), and [alpha-SiW12O40](5-/6-) redox couples in aqueous electrolyte media. The k(0) 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 ([alpha-SiW12O40](4-) and [alpha-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.