Effects of preparation on electrochemical properties of CoTMPP/C as catalyst for oxygen reduction reaction in acid media

Carbon supported Co tetramethoxy-phenylporphyrin (CoTMPP/C) catalysts have been synthesized by ultrasonic-assisted solvothermal method followed by heat-treatment in Ar atmosphere. The effects of preparation, including the solvent used for solvothermal reaction and the heat-treatment temperature, on electrochemical performance of the obtained CoTMPP/C catalysts towards oxygen reduction reaction (ORR) have been comparatively investigated. The results showed that the ORR peak potential could be improved by heat-treatment, it increases with increase in the calcination temperature, and then decreases when the heat-treatment temperature is larger than the optimal value, 600 °C, where the best catalytic activity could be achieved. Among the used solvents of glacial acetic acid (HAc), methylene chloride (CH2Cl2) and aqueous ammonia (NH3·H2O), the catalysts prepared with HAc and NH3·H2O demonstrated very close ORR peak potential and transferred-electron number, which are higher than that exhibited by the catalyst synthesized with CH2Cl2. However, considering from points of ORR peak potential, transferred-electron number, synthesis convenience and environmental adaption, we suggest that glacial acetic acid is the optimal solvent to prepare high performance CoTMPP/C catalyst for ORR.