3 research outputs found
Reversible Surface Two-Electron Transfer Reactions in Square Wave Voltcoulommetry: Application to the Study of the Reduction of Polyoxometalate [PMo<sub>12</sub>O<sub>40</sub>]<sup>3–</sup> Immobilized at a Boron Doped Diamond Electrode
Reversible surface two-electrons
transfer reactions (stepwise processes)
are analyzed using square
wave voltcoulommetry (SWVC), which is a variety of square wave techniques
based on the measurement of the transferred charge. Such reversible
surface redox processes are exhibited by many two-redox center and
multicenter biomolecules (proteins, enzymes, ...) and inorganic molecules
like polyoxometalates (POMs), which have very interesting applications,
mainly as electrocatalysts. Because of the stationary character of
the response obtained, the key parameters that govern the cooperativity
degree of the two reversible electron transfers (ETs) are the difference
between their formal potentials, Δ<i>E</i><sup>0</sup>, and the square wave amplitude, |<i>E</i><sub>SW</sub>|,
whose combined effect sets the two
peaks → one peak transition in the response. Working curves
based on the variation of the peak parameters (peak potentials, half-peak
widths, and peak heights) with Δ<i>E</i><sup>0</sup> and |<i>E</i><sub>SW</sub>| are given, from which the
formal potentials and the total surface excess can be accurately determined.
SWVC has been applied to the study of the reduction of polyoxometalate
[PMo<sub>12</sub>O<sub>40</sub>]<sup>3–</sup> adsorbed at a
boron doped diamond electrode (BDD), for which three stable and well-defined
reversible charge peaks, corresponding to three cooperative EE processes,
are obtained in the interval (0.6, −0.2) V by using low square
wave frequencies. From the analysis of these peaks, the values of
the total surface excess and the formal potentials of the six ETs
have been obtained in aqueous media for two electrolytes: HClO<sub>4</sub> and LiClO<sub>4</sub>