Electrochemical and physicochemical characterizations of methanol-tolerant platinum-macrocycle cocatalyst for oxygen reduction

Carbon supported iron tetraphenylporphyrin and platinum (FeTPP-Pt/C) cocatalysts were prepared by supporting FeTPP on Pt/C followed by a heat-treatment at temperatures ranging from 300 to 900 °C. The relationship of the electrocatalytic properties of cocatalysts and the heat-treatment temperature was studied in detail. Compared to the Pt/C counterpart, it was found that heat-treated cocatalysts exhibit a comparable catalytic activity for oxygen reduction reaction (ORR) and lower reactivity for methanol oxidation reaction (MOR). The cocatalysts treated at ca. 500–700 °C are, in our experimental conditions, the best ORR catalysts with high methanol tolerance. The physicochemical characterizations of the cocatalysts, Pt/C and FeTPP/C were performed by ICP-AES, TEM (EDX), XPS, and XRD techniques. Combined with the electrochemical results, it was revealed that the presence of Fe–N-based species surrounding the Pt sites could greatly hinder the MOR.