Application of a novel refinement method for accurate determination of chemical diffusion coefficients in electroactive materials by potential step technique

We describe application of a novel refinement method for an accurate determination of the chemical diffusion coefficient, D, and the generalized kinetic parameter, Lambda, from experimental potentiostatic intermittent titration technique (PITT) data suited for a variety of electrochemically doped electroactive polymers and inorganic intercalation host materials. The proposed, simple, two-step refinement procedure, based on earlier derived analytical expressions for the PITT response, is exemplified by the analysis of chronoamperometric responses to small-amplitude potential perturbation for p- and n-doped poly (fluorenonebithiophene) (PFDOBT-HH) thin film electrode. The initial p-doping and the entire region of n-doping of this polymer is characterized by a mixed kinetic control of the doping processes due to a combination of ohmic drops (in solution and in the bulk polymer), slow interfacial charge transfer, and diffusion kinetics. In these cases, the refinement procedure leads to meaningful values of the diffusion time constant, tau(d) and hence, D. It is believed that this relatively simple refinement procedure will facilitate accurate determination of the chemical diffusion coefficients of practical, composite insertion electrodes. (C) 2005 The Electrochemical Society.