Electrochemical behavior of hairy carbons Original Research Article

Hairy carbons were prepared by catalytic growth of carbon hairs (diameter 0.05–0.2 μm, at least partly crystalline) on carbon black, graphite particle and carbon fiber substrates. Of the substrates used, the most abundant hair growth was achieved using carbon black, due to the confinement of the catalyst size by the pores in the carbon black. The cyclic voltammetric response of all hairy carbons was superior to that of the corresponding substrate materials. In the case of hairy carbon black, reversibility was achieved and capacitance, electrochemical area and specific surface area were greatly decreased. In the case of hairy graphite particles and hairy carbon fibers, the electron transfer rate ks (as studied via the Fe2+Fe3+ redox couple) was increased, but, in contrast to the hairy carbon black, capacitance and electrochemical area were increased. Hair growth, followed by an oxidation heat-treatment, resulted in oxidized hairy carbon black which exhibited higher ks and better electrochemical reversibility than as-received carbon black, oxidized carbon black, hairy (but not oxidized) carbon black, carbon filaments (i.e. hair by itself) and hairy carbon fibers. This is partly due to the enhancement of the packing density by both hair growth and oxidation. The oxidized hairy carbon black exhibited much lower capacitance and much lower electrochemical area compared to as-received carbon black. The combination of high ks and low capacitance makes oxidized hairy carbon black technologically attractive for battery and analytical electrodes. The particulate nature of oxidized hairy carbon black is in contrast to the fibrous nature of carbon fibers or carbon filaments, which require secondary operations for dispersion. Additionally, hairy carbon black allows good compaction and electrochemical reversibility without the need for a binder.