Cobalt porphyrin–tungsten polyoxometalate anion as non-noble metal cathode catalyst in a fuel cell

Abstract

A mixture of a cationic cobalt 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin (CoPP) and an anionic metatungstate (POM) supported on graphite carbon was developed as a high performance novel cathode catalyst using a rotating ring-disk electrode for the oxygen reduction reaction (ORR) with high current density and low hydrogen peroxide production in a fuel cell. The CoPP-POM/carbon catalysts were characterized by XRD, X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy and BET surface area measurements. The 823 K-treated CoPP-POM/carbon catalyst exhibited the highest activity for the ORR at 0.85 V (RHE) at −0.005 mA cm⁻² and a current density of 1.55 mA cm⁻² at 0.8 V (RHE). The CoPP-POM/carbon exhibited an exchange current density of 2.28 × 10⁻⁹ mA cm⁻² and a H₂O₂ percentage of less than 5%. The metatungstate anion was coordinated with the cobalt porphyrin compound and adsorbed on the surface of the Vulcan carbon. The active species of the catalyst for the ORR were combined with the Co ions in the cobalt porphyrin compound and the metatungstate anion on the graphite.