Sanjeev Mukerjee

Electrocatalysis of Oxygen Reduction on Nonprecious Metallic Centers at High pH Environments

Iron(III) tetraphenyl porphyrin (FeTPP) macrocycle supported on high surface area Black Pearl Carbon prepared by ball milling and subsequent pyrolysis under inert atmosphere at 600{degree sign}C to 800{degree sign}C exhibits remarkable 4e- oxygen reduction reaction activity with minimal peroxide yield in alkaline medium. The pyrolytic evolution of the catalytic site has been systematically investigated using a combination of two powerful techniques, i) Square Wave Voltammetry (SWV) capable of isolating the Faradaic charge transfer from the non-Faradaic capacitive current and ii) in situ X-ray Absorption Near Edge Spectroscopy (XANES). Using these techniques we clearly show here clearly the two advantages obtained by pyrolysis in the case of FeTPP. i) Anodic shift in redox potential of the iron metal center and ii) the formation of a mixed-valence dimeric catalyst site capable of binding molecular oxygen and enable charge transfer in a concerted fashion.