Design of PGM-free ORR Catalysts: From Molecular to the State of the Art

The state-of-the-art Platinum group metal (PGM)-free oxygen reduction reaction (ORR) catalysts have been synthesized using the pyrolysis of iron, nitrogen, and carbon precursors, and result in highly active ORR catalysts, but their undefined structure limits their further development. Since the inspiration for these catalysts came from well-defined structures of transition metal complexes, it is important to understand the various parameters that govern the reaction potential, selectivity, and the stability with well-defined catalysts and try to extrapolate them to the pyrolyzed catalysts. In this chapter, we give an overview of the parameters that influence the catalysis of ORR with well-defined ORR catalysts. These can later be used to further enhance the performance of the state-of-the-art PGM-free ORR catalysts.