Electrocatalytic activity of metal phthalocyanines for oxygen reduction

A comparative study of the electrocatalytic activity of metallophthalocyanines for O2 reduction in alkaline and acid media was conducted using H2Pc, VOTsPc, CrTsPc, MnTsPc, MnPc, FeTsPc, FePc, FeMeOPc, CoTsPc, CoPc, CoMeOPc, CoTnPc and ZnTsPc adsorbed on OPG electrodes. Different electron-transfer mechanisms for O2 reduction were found depending on the position of the M(III)/ M(II) redox couples on the potential scale and the onset potential for O2 reduction. Volcano-shaped correlations between the redox potential and the O2 catalytic activity were observed. This has been rationalized on the basis of the redox catalysis concept and in terms of molecular orbital theory considerations.