After acid-treatment and addition of cobalt acetate followed by heat-treatment via ammonia gas at 900 ℃, the carbon black was produced into a gas diffusion electrode and its electro-catalytic performance for oxygen reduction improved greatly in 6 mol•L^－1 KOH electrolyte. The phase and structure of the produced sample were analyzed by X-ray diffraction and cobalt nitride (Co_5.47N) generated by adding cobalt acetate followed by heat-treatment with ammonia gas. The performance of gas diffusion electrodes for oxygen reduction reaction (ORR) in air was studied by polarization curves and AC impedance. At room temperature, the carbon electrode had no effect on ORR. After the carbon black was treated by acid, the current density for ORR in air achieved 57 mA•cm^－2 at potential of －0.2 V versus a Hg/HgO reference electrode. While the current density of 170 mA•cm^－2 of the Co-N/C complex electrode could be achieved in the same condition. AC impedance shows that because of the generation of cobalt nitride, the impedance of oxygen reduction greatly reduced, which was in favor of oxygen reduction. And the chronoamperometric curves indicate that the Co-N/C complex electrode exhibits high catalytic activity and stability.

Key words: carbon electrode, oxygen reduction reaction, electro-catalysis, cobalt nitride, current density