Non-platinum oxygen reduction electrocatalysts based on carbon-supported metal-polythiophene composites

A series of carbon-supported metal-polythiophene composite (M-PTh/C) electrocatalysts are synthesized based on seven different non-Pt metals (M = Ir, Ru, Pd, Co, Fe, Ni, Sn) using chemical polymerization method. The electrocatalytic activity toward the oxygen reduction reaction (ORR) is characterized in acidic condition using rotating disk electrode voltammetry. Ir-, Ru-, and Pd-PTh/C show far more positive (ca. 700 mV) ORR onset potentials than Co-, Fe-, Ni-, and Sn-PTh/C. Further studies on the ORR kinetics are carried out for the three superior catalysts, Ir-, Ru-, Pd-PTh/C, using Koutecky-Levich and Tafel plots. The number of electrons (n) transferred in the ORR is ∼4 for these three catalysts, suggesting 4-electron transfer ORR is dominant. Considering all the obtained factors (such as the onset potential, n value, and exchange current density), Ir- and Ru-PTh/C catalysts are concluded to have relatively excellent ORR catalytic activity.