Oxygen Electroreduction on Ti- and Fe-Containing Carbon Fibers

Abstract

A mixture of iron (II) phthalocyanine and polyacrylonitrile (PAN) was electrospun into fibers and pyrolyzed to form Fe-containing carbon fibers (Fe-PAN). Subsequent atomic layer deposition (ALD) coated the fibers with TiOy deposits (TiOy-Fe-PAN). Scanning transmission electron microscopy equipped with energy dispersive spectroscopy (STEM-EDS) detected C, Fe, and Ti across the diameter of the fiber, and X-ray photoelectron spectroscopy (XPS) revealed Fe(III) and CNx species present. After the ALD process, XPS revealed TiOy species on the Fe-PAN fibers, and heat-treating the TiOy-Fe-PAN samples created TiNxOy and TiNx species. Heat-treating Fe-PAN and TiOy-Fe-PAN samples resulted in a slight decrease in the Fe wt.% but affected an increase in the oxygen reduction reaction (ORR) activity in 0.5M H2SO4 at room temperature compared to the samples not heat treated. Moreover, the presence of Ti species decreased the production of H2O2 and increased the mass activity of the ORR on fibers subjected to cyclic potential excursions relative to samples without Ti species.