Metallic cobalt was deposited on acetylene black to synthesize a composite Co/C by chemical reduction method.A platinum-free electrocatalyst Co-N/C(8 0 0)for oxygen reduction reaction(ORR)was synthesized by mixing the composite Co/C with urea and heat-treating at 800 ℃.The results from linear sweep voltammograms indicated that the Co-N/C(800)is active to ORR.Theβ-Co and cobalt oxides are not the active site of the catalyst Co-N/C.However,the existence of cobalt facilitated the modification of nitrogen to carbon black and led to the formation of active site of catalyst Co-N/C(800).