Role of Nitrogen Precursor on the Activity Descriptor towards Oxygen Reduction Reaction in Iron-Based Catalysts

Nitrogen-doped carbon nanostructures supported non-precious transition metal/metal oxide electrocatalysts are promising alternative to platinum-based electrocatalysts for oxygen reduction reaction (ORR) of polymer electrolyte membrane fuel cell (PEMFC). In this article, a variety of nitrogen-doped carbon- iron based electrocatalysts were prepared by pyrolyzing a particular nitrogen-containing precursor compound with iron oxide at various reaction conditions using hydrothermal method. Our experimental data showed that the ratio between nitrogen containing precursor and metal ions plays significant role in determining the performance of ORR. The increase in nitrogen containing active sites is not linearly proportional to the quantity of nitrogenous precursor. Careful investigation by different spectroscopic (e. g. X-ray photoelectron spectroscopy, Raman Spectroscopy) as well as microscopic techniques along with electrochemical studies, we can conclude that- (a) nitrogen precursor in the synthesis process plays significant role in determining the morphology and oxidation state of iron in final catalyst; and (b) the overall electrocatalytic behaviour of Fe-N−C based electrocatalysts are largely dependent upon the oxidation state and morphology of catalyst.