AN IN-SITU RAMAN-SPECTROSCOPIC STUDY OF ELECTROCHEMICAL PROCESSES IN MERCURY-SOLUTION INTERPHASES

Electrochemical processes in the mercury-solution interphase were prob ed by in situ spectroelectrochemical micro-Raman spectroscopy. This is the first report of the in situ characterization of electrochemical p rocesses for a pure mercury electrode by Raman spectroscopy. Mercury w as oxidized in 0.1 M KClO4 solution, in the presence and absence of py ridine. Raman spectra, at several applied potentials, of the soluble o xidation products present in the mercury/solution interphase were reco rded. The aquated Hg-2(2+) [mercury(I)] cation was the only product ob served for mercury oxidation in the absence of pyridine. This cation w as characterized by the Hg-Hg stretch band at ca. 175 cm(-1). An Hg-2( 2+)-ClO4- precipitate was formed on the electrode surface at very anod ic potentials. The oxidation of mercury in the presence of pyridine re sulted in the formation of soluble mercury(II)-pyridine complexes in t he interphase. Characteristic Raman bands of these complexes were obse rved at ca. 1023 and 1048 cm(-1). Solution Raman experiments demonstra ted that a mixture of mercury(ll)-pyridine complexes [of general formu la Hg(py)(n)(2+), where 1 < n < 4] was produced in the interphase. (C) 1998 John Whey & Sons, Ltd.