Development of high performance carbon composite catalyst for oxygen reduction reaction in PEM Proton Exchange Membrane fuel cells

Highly active and stable carbon composite catalysts for oxygen reduction in PEM fuel cells were developed through the high-temperature pyrolysis of Co-Fe-N chelate complex, followed by the chemical post-treatment. A metal-free carbon catalyst was used as the Support. The carbon composite catalyst showed ail onset potential for oxygen reduction as high as 0.87V (NHE) in H2SO4 solution, and generated less than 1% H2O2. The PEM fuel cell exhibited a current density as high as 0.27 Acm(-2) at 0.6V and 2.3 Acm(-2) at 0.2V for a catalyst loading of 6.0 mg cm(-2). No significant performance degradation was observed over 480 h of continuous fuel cell operation wit h 2 mg cm(-2) Catalyst under a load of 200 mA cm(-2) as evidenced by a resulting cell voltage of 0.32V with a voltage decay rate of 80 mu Vh(-1). Materials characterization studies indicated that the metal-nitrogen chelate complexes decompose at high pyrolysis temperatures above 800 degrees C. resulting ill the formation of the metallic species. During the pyrolysis, the transition metals facilitate the incorporation of pyridinic and graphitic nitrogen groups into the carbon matrix, and the carbon Surface doped with nitrogen groups is catalytically active for oxygen reduction. (C) 2008 Elsevier B.V. All rights reserved.