The effect of the interfacial potential distribution on the reduction of adsorbed methylene blue at a mercury electrode

The constant current chronopotentiometric reduction of methylene blue adsorbed on a HMDE at fractional coverages of MB+ of theta less than or equal to 1 is reported and the results interpreted in terms of both an EE mechanism and the interfacial potential distribution (IPD) model of Smith and White (Anal. Chem., 64 (1992) 2398). Derivative chronopotentiometric (DCP) peaks were broader than expected for a two electron transfer under Langmuir isotherm conditions and shifted positively with increasing fractional coverage. Whilst the EE model satisfactorily accounted for the peak shape and was in general agreement with previously reported work (Zutic et al., J. Electroanal. Chem., 177 (1984) 253) it was not possible to account for the shift in the DCP peak. Calculated DCPs based on the IPD model had peak shapes consistent with the experimental DCPs and shifted positively with increasing fractional coverage in the manner of the experimental DCPs. (C) 1998 Elsevier Science S.A. All rights reserved.