Oxygen Reduction Reaction on Carbon Supported Pt and Pd in Alkaline Solutions

Carbon-supported Pt and Pd (20 wt % metal) were employed as oxygen reduction catalysts in 0.1 M NaOH solutions. Results from X-ray diffraction analysis show that the metals are in the form of Pt face-centered cubic (fcc) and Pd (fcc) crystal only. The metal particles were observed to distribute uniformly on carbon supports, and the average particle size of the Pd and the Pt was 3.1 and 2.3 nm, respectively, from the transmission electron microscopy image analysis. The Pd/C catalyst showed high activity toward the oxygen reduction reaction (ORR) both at room and elevated temperatures (up to 60 degrees C) compared with the Pt/C. The activation energies for the ORR on the Pd/C are slightly lower than that on the Pt/C (39 vs 48 kJ mol(-1) at the overpotential of 0.3 V). The four-electron path is dominant on both the Pt/C and the Pd/C. The H2O2 yields on both catalysts are analyzed in detail. As a cathode fuel cell catalyst, the Pd/C catalyst is less sensitive to alcohol contamination as compared to Pt/C. The challenges for using Pd/C as an ORR catalyst in alkaline solution, are also discussed in this paper. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3058586] All rights reserved.