BARRIER PROPERTIES OF A THIN-FILM OF 4-PENTADECYLPYRIDINE COATED AT AU(111) ELECTRODE SURFACE

The reduction of Fe(CN)(6)(3-) at the Au(111) electrode coated with a thin film of 4-pentadecylpyridine (C15-4-Py) was investigated. The C15-4-Py molecules form a multilayer at the Au(111) surface which may be repeatedly adsorbed and desorbed by varying the electrode potential. At E > -0.2 V (SCE) the film has a very compact structure. Its capacity is lower than 1 mu F cm(-2) and it exhibits strong blocking behavior with respect to the reduction of Fe(CN)(6)(3-). At potentials -0.6 V (SCE) < E < -0.3 V (SCE) the film is less rigid. Its capacity increases to about 2 mu F cm(-2) and it is more porous. The rate of Fe(CN)(6)(3-) reduction at the film covered electrode is characteristic of nonlinear diffusion to active pores separated by inactive areas. The average pore size changes between 10 mu m and about 30 mu m and the pore separation varies between 200 and 500 mu m for -0.6 V (SCE) < E < -0.3 V (SCE). In this range the pore density changes from 100 to 6 x 10(3) pores/cm(2).