Fe/carbon nanofiber composite materials for Fe–air battery anodes

• The morphology of carbons and their characteristics strongly affect the cycling performance of Fe/C electrodes.
• Iron was dispersed as small species on the Fe/C electrode surface during cycling.
• The capacities of the Fe/C electrodes were improved with K2S additive.

We investigated the effects of carbon materials on the electrochemical properties of iron electrodes in alkaline solution with the use of cyclic voltammetry (CV), galvanostatic cycling performance, and scanning electron microscopy (SEM) together with X-ray energy-dispersive spectroscopy (EDS). Various herringbone-type carbons were used as additives to investigate the effects of carbon materials on the electrochemical properties of iron electrodes to find an adequate carbon for use in Fe-air battery anodes. An Fe/C composite electrode showed significant performance improvement over a pure iron electrode when herringbone carbon nanofibers (CNFs) were employed. The morphology of carbons as well as their characteristics strongly affected the cycling performance of the Fe/C composite electrodes. Our X-ray energy dispersive spectroscopy (EDS) study showed that during cycling, iron species were dispersed on the carbon surface. Such dispersion of iron may improve the electrochemical behavior of the Fe redox species. When K2S additive was added to the electrolyte, the hydrogen evolution was significantly suppressed and the capacities of the Fe/C electrodes were improved.