Ferrous hydroxide Fe(OH)(2) gel was adsorbed on carbon black to produce Fe(OH)(2)/C. Various N-containing precursors were then either adsorbed on this material before pyrolysis at 1000 degrees C in Ar or introduced as vapors in the reactor during the pyrolysis step. The N-containing precursors adsorbed on Fe(OH)(2)/C were either polyacrylonitrile (PAN), tetracyanoquinodimethane (TCNQ), or metal-free phthalocyanine (H2Pc), while the N-containing vapors injected into the reactor were acetonitrile (CH3CN) or ammonia (NH3). The resulting materials were characterized by X-ray diffraction analysis, transmission electron microscopy, and X-ray photoelectron spectroscopy. Their electrochemical activities for O-2 reduction were determined using a rotating disk electrode in O-2-saturated H2SO4 at pH 0.5. Upon heating, Fe(OH)(2)/C is mostly transformed into iron carbide aggregates. Adding a N-containing species during the pyrolysis of Fe(OH)(2)/C is essential for obtaining catalytic activity of O-2 reduction. However, all N-containing precursors are not equivalent. The catalytic activity increases along the series : PAN < TCNQ < H2Pc. This series also represents an increasing polarizability of the N-containing precursor. The effect of NH3 and CH3CN vapors are equivalent, yielding slightly higher electroactivities than those obtained with adsorbed PAN. All N-containirig precursors generate pyrolysis products containing C and N atoms. This is also true for NH3 vapors since NH3 reacts with the carbon support at 1000 degrees C. Deconvolution of the N-1s core level spectra of the catalytic materials leads to the identification of three separate contributions assigned to pyridinic, pyrrolic, and graphitic-type nitrogens. It is demonstrated that none of these N-type contributions alone seem to be responsible for the catalytic activity.