OXYGEN REDUCTION IN ACID-MEDIA - INFLUENCE OF THE ACTIVITY OF CONPC(1,2) BILAYER DEPOSITS IN RELATION TO THEIR ATTACHMENT TO THE CARBON-BLACK SUPPORT AND ROLE OF SURFACE GROUPS AS A FUNCTION OF HEAT-TREATMENT

O2 reduction was investigated using rotating disk electrode and voltammetry techniques on NPcCo(1,2) impregnations deposited onto two kinds of carbon black support. They were selected on the basis of their similar pH and dibuthylphthalate (DBP) adsorption values. Samples were also characterized by IR and X-ray photoelectron spectroscopy techniques. An optimized thermal treatment yielded an improvement in the O2 reducibility and identical activities (with N = 3.8) on both supports. These spectroscopic methods revealed a bilayer structure and suggested the presence of two sorts of site (active and inactive) which differed in their attachment of the substrate via surface groups which were characterized.