Iron-based catalysts for the oxygen reduction reaction (ORR) were produced by pyrolysis of iron-acetate and Ketienblack (R) carbon with varying amounts of 2,2'-bipyridine in a closed, constant-volume vessel. The total surface nitrogen content detected by XPS varied from 0.6 to 2.2 at% when the nitrogen precursor loading was varied from 1.5 to 11.3 wt%. The amount of nitrogen in the Fe-pyridinic form is estimated to vary between 0.12 and 0.24 at%, correlating to catalytic activity (current density) variation from 0.07 to 1.9 mA cm(-2) at a catalyst loading of 0.5 Mg cm(-2). These results support the theory that iron associated with pyridinic nitrogen is a component of the catalytic active site responsible for oxygen reduction. (C) 2009 Elsevier B.V. All rights reserved.