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 ele ctrodes previously subjected to a constant applied potential of 0.7 V( RHE) in the hot H3PO4 Solution. The faradaic reactions on the catalyze d platinum were inhibited by the selective adsorption of iodide ions o nto the platinum surface. The anodic current peak increased with incre asing ageing time in the hot H3PO4 solution. Oxygen-blowing reduced th e amount of the surface oxide and at the same time the rate of the sur face oxide formation as compared to nitrogen-blowing. The results of t he surface oxide amount determined by linear sweep voltammetry analysi s were substantiated by FTIR spectroscopy. With recognition of the car bon surface oxide formation, followed by the CO2 evolution, it is sugg ested that the reaction products, such as water molecules, generated d ue to oxygen reduction on the dispersed platinum surface facilitate th e CO2 evolution rather the surface oxide formation on carbon surface i n 145-degrees-C, 85% H3PO4 solution at 0.7 V(RHE).