EFFECT OF HYDROGEN-FLUORIDE ON THE ANODIC BEHAVIOR OF GLASSY-CARBON IN AQUEOUS AND MIXED AQUEOUS-SOLUTIONS

The electrochemical behavior of the glassy carbon electrode (GCE) in aqueous 1.0-20.0 M HF solutions and in mixed solvents containing 15.0 M HF (25 vol.%) was investigated using cyclic voltammetry, chronoamperometry, and surface microscopic analysis. The GCE shows three surface redox peaks in aqueous HF solutions which become distinct at higher HF concentrations. Fresh surface oxidation and slight surface roughening occurs above 1.6 V. The background current increases significantly due to strong anodic polarisation in HF solutions. However, the electrode activity as measured by the response of the ferricyanide/ferrocyanide redox system remains unaltered. In mixed solvent systems, the surface redox currents and fresh surface oxidation decrease significantly. The oxygen evolution occurs at less positive potentials. Thus the electrochemical activity in such systems is much better.