An In situ Spectroscopic Study of Raman Electrochemical Processes in Mercury–Solution Interphases

Electrochemical processes in the mercury–solution interphase were probed by in situ spectroelectrochemical microRaman spectroscopy. This is the Ðrst report of the in situ characterization of electrochemical processes for a pure mercury electrode by Raman spectroscopy. Mercury was oxidized in 0.1 M solution, in the presence and KClO 4 absence of pyridine. Raman spectra, at several applied potentials, of the soluble oxidation products present in the mercury/solution interphase were recorded. The aquated [mercury(I) ] cation was the only product observed Hg 2 2‘ for mercury oxidation in the absence of pyridine. This cation was characterized by the Hg–Hg stretch band at ca. 175 cm—1. An precipitate was formed on the electrode surface at very anodic potentials. The oxidaHg 2 2‘–ClO 4 — tion of mercury in the presence of pyridine resulted in the formation of soluble mercury(II)–pyridine complexes in the interphase. Characteristic Raman bands of these complexes were observed at ca. 1023 and 1048 cm—1. Solution Raman experiments demonstrated that a mixture of mercury(II)–pyridine complexes [of general formula where 1 Æ n Æ 4 ] was produced in the interphase. 1998 John Wiley & Sons, Ltd. Hg(py) n 2‘, (