Effect of Dissolved Iron on Oxygen Reduction at a Pt/C Electrode in Sulfuric Acid

The activity of Pt supported on Vulcan XC-72R carbon catalyst for oxygen reduction in the absence and presence of dissolved Fe in 0.5 M H 2 SO 4 was measured. The Pt / C catalyst in sulfuric acid with dissolved Fe in the electrolyte was far more active for oxygen reduction than those without dissolved Fe . The activity of Pt / C for oxygen reduction in 0.5 M H 2 SO 4 in the presence of 100 ppm dissolved Fe is doubled at 70 ° C , O 2 at 0.6 V vs. a standard hydrogen electrode. The mechanism of enhancement is due to the reaction of dissolved Fe and H 2 O 2 to form Fe ( III ) hydroperoxy complexes, followed by the heterogeneous decomposition on Pt to release O 2 .