Influence of Sulfur on the Pyrolysis of CoTMPP as Electrocatalyst for the Oxygen Reduction Reaction

Abstract

The prepn. of pyrolyzed Co tetramethoxyphenylporphyrin (CoTMPP), supported by Fe oxalate with and without S as electrocatalysts, for the O redn. reaction (ORR) in acid media, was studied. A prepn. which needs no addn. of C supports allows the structural study of the pyrolysis products by x-ray photoemission spectroscopy, Raman spectroscopy, and XRD without interferences of the C support. With low metal loading, rotating ring disk electrode measurements reveal the high ORR activity and enhanced selectivity which are apparently caused by an increased no. of catalytic centers and higher efficient ones due to a well-developed porosity and a suitable mol. structure of the formed C. A thermogravimetric study of the pyrolysis process shows that the addn. of S to the precursor influences the carbonization of the porphyrin in a favorable way. Extended graphene layers present a suitable matrix for active catalytic centers. [on SciFinder(R)]