Oxygen electroreduction on Fe- or Co-containing carbon fibers

Abstract

Non-noble metal-containing electrocatalysts were prepared by an electrospinning method and evaluated as oxygen reduction electrocatalysts. Fe- or Co-containing carbon fibers were prepared by pyrolyzing electrospun polyacrylonitrile (PAN) fibers containing the respective metal precursor and are denoted Fe-PAN and Co-PAN, respectively. The Fe- or Co-PAN carbon fibers were acid-leached and subjected to a second pyrolysis, whereby the final fibers were found to be uniform in diameter with roughened surfaces. Scanning transmission electron microscopy equipped with energy dispersive spectroscopy area-mapping identified Fe or Co nanoparticulates throughout the fiber with a distribution of particulate sizes. X-ray diffractograms (XRD) revealed amorphous Fe-PAN and Co-PAN carbon fibers with no discernible Fe or Co phases, whereas high-resolution XPS scans show a range of potential Fe or Co species. Moreover, the high-resolution X-ray photoelectron spectroscopy (XPS) and peak-fitting analysis provided chemical species information for the C1s, N1s, Fe2p and Co2p regions. The physical characterizations highlighted potential beneficial components for the electrocatalysts that made their use as oxygen reduction reaction (ORR) effective. Rotating disk and ring-disk electrode experiments determined that the best Fe-PAN sample out-performed the best Co-PAN sample and even performed well in comparison to a commercial Pt/C electrocatalyst for the ORR in a high pH media.