A NEW FUEL-CELL ELECTROCATALYST BASED ON CARBONIZED POLYACRYLONITRILEFOAM - THE NATURE OF PLATINUM-SUPPORT INTERACTIONS

X-ray photoelectron spectroscopy (XPS) and transmission electron micro scopy (TEM) have been conducted on a new fuel cell electrocatalytic ma terial based on a highly porous carbonized polyacrylonitrile (PAN) mic rocellular foam with very low platinum loading (similar to 13 to 23 mu g cm(-2)). TEM images of this material clearly show the existence of nanometer size platinum particles which are homogeneously distributed in the highly porous carbonized PAN matrix. An XPS study of Pt-loaded PAN indicates that C 1s, O 1s, and N 1s peaks shift to lower binding e nergies, compared to virgin PAN. It was concluded that special metal-s upport interaction exists, through the formation of a charge-transfer complex between platinum and pyridine-type nitrogen atoms of PAN suppo rt. This interaction leads to the enhancement of the catalytic activit y, and the improvement of the long-time stability of this electrocatal yst.