Comparison of the Behavior of Several Cobalt Porphyrins as Electrocatalysts for the Reduction of O2 at Graphite Electrodes

作者：Eui-Hwan Song, Chunnian Shi, Fred C. Anson · 发表于：Langmuir · 年份：1998 · 被引用次数：183 · 研究领域：Porphyrin and Phthalocyanine Chemistry、Electrocatalysts for Energy Conversion、CO2 Reduction Techniques and Catalysts

Four cobalt porphyrins were adsorbed on graphite electrodes and used to catalyze the electroreduction of O 2 . The two porphyrins without substituent groups in the meso positions of the porphyrin ring operated at the most positive potentials and catalyzed the reduction of O 2 to both H 2 O 2 and H 2 O, but the H 2 O did not result from significant reduction of H 2 O 2 . The porphyrins containing meso substituents catalyzed only the reduction of O 2 to H 2 O 2 . The catalysts that accomplish the four-electron reduction of O 2 are argued to consist of dimeric (or higher oligomeric) forms of the adsorbed porphyrins. The present results and those of two recent related studies 1,2 indicate that the presence of only hydrogen or small alkyl groups in the meso positions of porphyrin rings facilitates the spontaneous formation of van der Waals dimers with greater catalytic activity for the reduction of O 2 by four electrons. Such cobalt porphyrins were also found to be unusually active catalysts for the electro-oxidation of H 2 O 2 .