Mass Transport Properties of Silicified Graphite Felt
Electrodes
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Abstract
Mass
transport properties of electrodes prepared from graphite
felt, as such and after silicification, have been studied using cyclic
voltammetry. Within the graphite felt, the mass transport of a probe
changes with decreasing scan rate, from a radial diffusion around
fibers to a regime that is analogous to “thin-layer”
systems. Furthermore, unlike classical “thin-layer”
systems, the volume comprised in the felt is macroscopic (resulting
in high current densities), while the time required to consume all
diffusive species remains in the 1 min range. Silicification of graphite
felt does not impact on the mass transport of the negatively charged
molecular probe Fe(CN)<sub>6</sub><sup>3–</sup> but significantly
slows mass transport of positively charged Ru(NH<sub>3</sub>)<sub>6</sub><sup>3+</sup>. In the latter case, a parallel decrease of
peak current intensity reflects limited mobility of the probe due
to its strong interaction with the surface of the pore walls. These
data provide important information for the optimization of the working
conditions of these electrodes for the design of biosensors and biofuel
cells