Electrochemical properties of a thermally expanded magnetic graphene composite with a conductive polymer

Abstract

A magnetic graphene composite derived from stage-1 FeCl3-graphite intercalation compounds was thermally treated for up to 75 min at 400 °C or for 2 min at high temperatures up to 900 °C. These heat-treatments of the magnetic graphene composite gave rise to the cubical expansion of graphene with the enlargement of inter-graphene distances. The specific capacitance of the magnetic graphene composite increased upon heating and reached 42 F g-1 at a scan rate of 5 mV s-1 in 1.0 M NaCl, after being treated for 2 min at 900 °C. This value corresponds to 840% increase in the capacitance activity superior to that (5 F g-1) of the pristine magnetic graphene composite before heat-treatment. This capacitance enhancement can play a significant role in the increase of the surface area that reached 17.2 m2 g-1 during the non-defective inter-graphene exfoliation. Moreover, the magnetic graphene composite heated at 900 °C was hybridized with polyaniline by in situ polymerization of aniline to reach a specific capacitance of 253 F g-1 at 5 mV s-1. The current procedure of heat-treatment and hybridization with a conductive polymer can be an effective method for attaining a well-expanded magnetic graphene composite possessing an enhanced electrochemical activity with a relatively high energy density (141 W h kg-1 in 1.0 M NaCl) and an excellent stability (99% after 9000 cycles of 20 A g-1).