Adsorption of Benzo‐(f)‐Quinoline on Gold and the Kinetics of the Quinone‐Hydroquinone and the Iron(III)/Iron(II) Systems

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Abstract
The adsorption of benzo‐(f)‐quinoline on gold electrodes in was estimated from differential capacity data. Between 0.0 and +0.7V adsorption is nearly independent of potential and can be fitted equally well to the Frumkin isotherm and to the isotherm with virial coefficients, . Apparent standard rate constants for the quinone‐hydroquinone system were obtained from low overpotential (±20 mV) and those for the Fe(III)‐Fe(II) system from impedance (20–800 Hz) measurements. For the quinone‐hydroquinone system the rate constant decreases exponentially with benzo‐(f)‐quinoline coverage from at to at . For the Fe(III)‐Fe(II) system the decrease is from at to at , again exponential in θ. The decrease cannot be explained by changes in the outer Helmholtz plane, , caused by benzo‐(f)‐quinoline, since calculated for the quinone‐hydroquinone system are 3 to 4 times larger than those obtained for Fe(III)‐Fe(II). The decreases are ascribed to changes in free energy of activation due to interaction between the adsorbed layer and electroactive species.

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