(544hd) Nitrogen-Doped Carbon Nanostructures As Bifunctional Catalysts for Unitized Regenerative PEM Fuel Cells
Electrocatalytic activity measurements demonstrate much better bifunctional ORR and OER characteristics of CNx compared to state-of-the-art Pt and Ir-based materials2. CNx catalysts are also resistant to poisoning in the presence of CO, H2S and CN-, indicating the absence of a metal-centered active site3. We have recently identified that phosphate anions (H2PO4-) can be used as poisoning probes for investigating nature of active sites in CNx catalysts4. Ex-situ and in-situ electrocatalytic measurements reveal a decrease in ORR activity after exposure to phosphate anions. X-ray photoelectron spectroscopy (XPS), Raman and infrared spectroscopy shed light on the poisoning phenomenon in CNx and help identify two possible active sites. Pyridinic nitrogen content in CNx catalysts is varied by changing the pyrolysis temperature. ORR and OER activity, and therefore, the bifunctional characteristics of CNx catalysts are found to vary with varying pyridinic nitrogen site density in the CNx samples2.
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