ELECTROCHEMICAL-BEHAVIOR OF ELECTRODES MODIFIED WITH PI-CONJUGATED POLYMERS IN 0.5 M H2SO4 (AQ) AND 1 M KOH (AQ) ELECTROLYTES

Plantinum electrodes modified with 10 kinds of ?c-conjugated polymers have been prepared. These polymers include poly(pyridine-2,5-diyl) PPy , poly(2,2'-bipyridine-5,5'-diyl) PBpy, poly(3-octylthiophene-2,5-diyl ) P30cTh, and poly(6-hexylpyridine-2,5-diyl) P6HexPy. Films of PPy and PBpy behave as good H+-transporting materials in 0.5 M H2SO4 (aq). Pl ots of log i vs. V for electrodes modified with the polymers give line ar lines in a current density region of 10(-5.5)-10(-2) A cm(-2). The slope of the line, beta=dV/d(log i), depends on the kind of the polyme r. Hydrophilic PPy and PBpy give a beta value of 3.2x10(-2) V, while h ydrophobic P30cTh and P6HexPy with long alkyl chains give a larger bet a value of 4.5x10(-2) V. Diffusion coefficients of H+ in films of PPy, PBpy, and poly(quinoline-2,6-diyl) P(2,6-Q) are estimated to be large r than 10(-7) cm(2) s(-1) from limiting currents at room temperature. The i-V curve of a P(2,6-Q)-modified Pt electrode shows a strong pH-de pendence reflecting a chemical change of the polymer with pH. The PPy- , PBpy-, and P3OcTh-modified Pt electrodes exhibit acceleration effect s for evolution of O-2 from 1 M KOH (aq).