Non-noble metal-based catalysts for the reduction of oxygen in polymer electrolyte fuel cells

Abstract

Catalysts for oxygen reduction are obtained from the pyrolysis of V, Cr, Fe, and Co hydroxides adsorbed on carbon black. The catalyst preparation procedure consists of reducing at 600°C the corresponding hydroxides in H2 (or in H2 + NH3), and subsequently applying a heat-treatment at 1000°C in acetonitrile vapor. Acetonitrile is used as a nitrogen containing precursor. When the same procedure is followed with Ti, Mn, Ni, Cu, or Mo hydroxides adsorbed on carbon black, materials with very little activity are obtained. All prepared materials were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The nominal metal content was always 10%. Changes in the metal contents following pyrolysis was determined by neutron activation analysis (NAA). The electrochemical properties of these materials for oxygen reduction was determined by rotating disk electrode in H2SO4 solution. The catalytic activity increases according to the following sequence: V ≪3Co