CORROSION BEHAVIOR OF PLATINUM-CATALYZED CARBON IN PHOSPHORIC-ACID SOLUTION

The effects of gaseous oxygen have been investigated on the corrosion behaviour of platinum-free and platinum-catalyzed carbon electrodes in 85% H3PO4 solution at 145-degrees-C by using linear sweep voltammetry in connection with FTIR (Fourier Transform Infrared) spectroscopy at room temperature. Linear sweep voltammetry experiments were made in IM H2SO4 solution on the platinum-free and platinum-catalyzed carbon electrodes previously subjected to a constant applied potential of 0.7 V(RHE) in the hot H3PO4 Solution. The faradaic reactions on the catalyzed platinum were inhibited by the selective adsorption of iodide ions onto the platinum surface. The anodic current peak increased with increasing ageing time in the hot H3PO4 solution. Oxygen-blowing reduced the amount of the surface oxide and at the same time the rate of the surface oxide formation as compared to nitrogen-blowing. The results of the surface oxide amount determined by linear sweep voltammetry analysis were substantiated by FTIR spectroscopy. With recognition of the carbon surface oxide formation, followed by the CO2 evolution, it is suggested that the reaction products, such as water molecules, generated due to oxygen reduction on the dispersed platinum surface facilitate the CO2 evolution rather the surface oxide formation on carbon surface in 145-degrees-C, 85% H3PO4 solution at 0.7 V(RHE).