3D non-precious metal-based electrocatalysts for the oxygen reduction reaction in acid media

A series of non-precious metal catalysts for oxygen reduction reaction (ORR) in PEMFCs are prepared by pyrolysis of different precursors at 800 °C under an Ar atmosphere. These precursors are 3d transition metal triethylenetetramine chelates supported on carbon (MTETA/C, M = Fe, Co, Ni, Cu, Zn and Mn). Results by XRD and TEM indicate that the catalyst transforms to a carbon structure embedded with metal or metallic carbon after pyrolysis. Electrochemical measurements are achieved by rotating disk electrode and cycle voltammograms in 0.5 M H₂SO₄ solution, as well as single cell tests. The catalytic activities decreases as Fe > Co > Zn > Mn > metal-free >>Cu > > Ni. This suggests that the transition metal plays an important role in formation of the active sites. Single cell tests show that they have some potential applications as the cathode catalysts. Some potential catalytic active sites are also propounded.