Using Magnetometry to Understand the Relative Role of Magnetic Particles in Co-Based Catalysts for the Oxygen Reduction Reaction

Magnetometry is used in conjunction with voltammetry, microscopy, and photoemission spectroscopy to examine the effect of different preparations on the activity of pyrolyzed Co-based catalysts for the oxygen reduction reaction. Preparations involving only a metal-organic framework (MOF)-based precursor contain primarily paramagnetic species with the addition of a small amount of nonparamagnetic Co consistent with the presence of a small amount (5%) of Co nanoparticles. Addition of the surfactant cetyltrimethylammonium bromide (CTAB) to the MOF precursor results in the presence of ca. 50% nanoparticles in the sample, likely due to the agglomeration of Co during catalyst precursor synthesis. Changes in the amount of Co nanoparticles do not correlate with major changes in ORR parameters such as E1/2 or peroxide formation amount in either acidic or basic electrolyte.