Abstract: Carbon black EC 300J (KB) with high mesoporous area and electrical conductivity was used as support for cobalt tetramethoxyphenylporphyrin (CoTMPP) to prepare the cathode electrocatalysts (CoTMPP/KB) for the oxygen reduction in proton exchange membrane fuel cell (PEMFC). The influence of chemical pretreatment of carbon black supports and 900 ℃ heat-treating of the electrocatalysts on the electrocatalytic activities for oxygen reduction of CoTMPP/KB were investigated by cyclic voltammogram (CV). Results show that with 6 mol?L-1 HNO3 pretreatment of carbon support and 900 ℃ heat-treatment of the catalyst, although the pyrolysis occurred for the CoTMPP structure, the electrocatalyst shows the best catalytic performance for oxygen reduction, both the cathodic peak potential ( Ep ) and the maximum capacitive current ( Ip ) have been improved. The surface properties and the microstructures of both the carbon black KB and the electrocatalyst have been investigated by IR, XRD, TEM and nitrogen adsorption/desorption. After the pretreatment with 6 mol?L-1 HNO3, the concentration of hydroxyl group and other oxygen-groups has been increased on KB surface and no obvious particle aggregation of KB has been observed, an average particle size of about 30 nm of KB has been observed; The pore structure of the catalysts is mainly composed of mesopores and has a narrow pore size distribution, which prove CoTMPP/KB to be a good electrocatalyst; CoC3 (101) and metallic Co(111) have been formed in the catalyst after 900 ℃ heat-treatment, and the cobalt ions have been well dispersed in the carbon black surface, with mean pore size of 8.2 nm and surface area of 463.4 m2?g-1.

Key words: Ketjen Black EC 300J, CoTMPP/KB, Pretreatment, Heat-treatment, CV, Oxygen reduction