EFFECTS OF ETHYLENE-GLYCOL (EG) CONCENTRATION AND PH OF SOLUTIONS ON ELECTROCATALYTIC PROPERTIES OF PT(111) ELECTRODE IN EG OXIDATION - A COMPARISON STUDY WITH ADJACENT PLANES OF PLATINUM SINGLE-CRYSTAL SITUATED IN [1(1)OVER-BAR-0] AND [01(1)OVER-BAR] CRYSTALLOGRAPHIC ZONES

The electrocatalytic properties of Pt(111) electrodes towards ethylene glycol (EG) oxidation was investigated mainly by cyclic voltammetry. The effects of the concentration of EG and the pH of the solutions wer e highlighted. The electrocatalytic activity of the Pt(111) electrode has been compared to those of platinum single crystal electrodes with their orientation situated adjacent to Pt(111) in [110BAR] and [011BAR ] crystallographic zones. It has been found that Pt(111) electrodes wi th well-defined surfaces are very sensitive to the acid-base propertie s of investigated solutions, nevertheless its activity is smaller than that of Pt(111) electrodes with disordered surfaces. It has been demo nstrated that OH- species may participate in the oxidation process of EG on Pt(111), and that an apparent degree of reaction for OH- in the oxidation was evaluated at 0.83 in dilute base solutions. The effects of EG concentration illustrated further that EG electrocatalytic oxida tion is a surface dependent reaction, where the rate determining steps may be attributed mainly to adsorption processes of EG and intermedia tes generated in the oxidation.