OXYGEN REDUCTION ON A NEW ELECTROCATALYST BASED ON HIGHLY POROUS CARBONIZED POLYACRYLONITRILE MICROCELLULAR FOAM WITH VERY-LOW PLATINUM LOADING

A highly porous carbonized polyacrylonitrile microcellular foam with v ery low platinum loading (approximately 13 to 23 mu g cm(-2)) was prep ared for use as a possible electrode material in a fuel cell system, T he effective surface area of platinum at the PAN/Pt electrode is estim ated to be about 1.4 times the geometric area of the substrate electro de. The average particle size deduced from the electrochemical measure ments is 44.9 nm. The electrochemical reduction of oxygen was studied at this material by using the rotating disk electrode method, Scanning electron microscopic images of this material clearly show the existen ce of nanometer sized platinum particles that are homogeneously distri buted. These platinum particles are somewhat ''isolated'' from each ot her, within the carbonized PAN matrix that is highly porous with a por e size ranging from ca. 1 to 10 mu m. The reaction order for the oxyge n reduction on this material is unity. The results show that the O-2 r eduction at the PAN/Pt electrode involves an overall transfer of four electrons per O-2 molecule consumed.