A Molecular Theory of Chemically Modified Electrodes by Redox Polyelectrolytes under Reversible

CALVO EJ,; SZLEIFER, IGAL; TAGLIAZUCCHI, MARIO

Banff, Alberta, CANADA

Congreso; 58th Annual Meeting of the International Society of Electrochemistry; 2007

International Society of Electrochemistry (ISE)

A molecular theory of chemically modified electrodes by redox polyelectroytes explicitly includes the size, shape, charge distribution, and conformations of all of the molecular species in the system, chemically equilibria and intermolecular interactions. An osmium pyridinebipyridine complex covalently bound to poly(allyl-amine) backbone (PAH-Os) adsorbed onto mercapto-propane sulfonate (MPS) thiolated gold electrode is described. The potential and electrolyte composition dependent redox and nonredox capacitance can be calculated with the molecular theory in very good agreement with voltammetric experiments under reversible conditions without the use of freely adjustable parameter. Unlike existing phenomenological models the theory links the electrochemical behavior and the structure of the polymer layer. Moreover, the theory predicts a highly inhomogeneous distribution of acid-base and redox states that strongly couples with the inhomogeneous distribution of molecular species in the nanometric redox film.