The electrochemistry of platinum phthalocyanine microcrystals I. Electrochemical behaviour in acetonitrile electrolytes

Platinum phthalocyanine (PtPc) microcrystals deposited upon platinum, glass y carbon and gold by a process of dry abrasion have been characterised by e lectrochemical techniques. This mechanical abrasion can produce good electr onic contact and adhesion between the microcrystals and the electrode. The redox process of PtPc microcrystals is accompanied by two reversible electr ochemical phase transformations, evidenced by a sharp peak and unusually la rge peak potential differences. Similar to conductive polymers, an obvious first-scan discrepancy and large capacitance are observed during electroche mical oxidation. Some of the intercalated anions remain in the re-reduced m icrocrystals and lead to a conductivity enhancement of the microcrystals, s upported by AC impedance and X-ray photoelectron spectroscopy (XPS) results . Coulometry shows that the size of the anion determines the rate and degre e of oxidation, and influences the reversible phase transformations. Chrono amperometry shows diffusion-controlled nucleation and growth kinetics, cont rolled by the diffusion of anions into the solid films. The conformational relaxation model was used to describe this process. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.