A Simple Preheating-Pyrolysis Strategy Leading to Superior Oxygen Reduction Reaction Activity in Fe-N/Carbon Black.

Maintaining the high catalytic activity of the oxygen reduction reaction (ORR) while reducing costs is a long-standing effort to promote the application of polymer electrolyte fuel cells. Here, the binding of nitrogen-containing ligands and carbon black is enhanced by controlling the pyrolysis conditions of a FeSO4 , 1,10-phenanthroline (phen), carbon black mixture, which significantly improves the ORR catalytic activity of the pyrolysis products. Preheating is proposed as a process improvement method using a heat treatment at a temperature between the melting and boiling points of phen before high-temperature pyrolysis, which achieves an effective combination of phen and carbon black, and enhances the interaction between phen and ferrous ions. This method substantially increases the number of FeNx active centers in the pyrolysis product, resulting in an impressive Fe-N/C catalyst with half-wave potential (E1/2 ) up to 0.93 V and a diffusion-limited current density (jL ) of 5.9 mA cm-2 and no obvious decay after 20 000 cyclic voltammetry cycles in 0.1 m KOH, which are all among the best-reported data known to date. The interaction between the ratio of Fe/phen and the pyrolysis conditions is also investigated. Under the right conditions, cheap raw materials can also generate highly catalytically active sites.