Enhancing the supercapacitor behaviour of novel Fe3O4/FeOOH nanowire hybrid electrodes in aqueous electrolytes

Abstract

A meso-porous composite electrode in which 1-dimensional FeOx nanowires and carbon nanotubes were intertwined has been fabricated using spray deposition. The electrodes showed the highest capacitance and best rate performance in an aqueous Na2SO3 electrolyte at 2 mV s−1 where electrochemically active SO32− ions contributed to a pseudocapacitance of over 300 F g−1, amongst the highest reported for iron oxide, which was maintained at >100 F g−1 up to fast scan rates of 250 mV s−1. Electrochemical testing and impedance spectroscopy in several aqueous electrolytes (Na2SO4, Li2SO4, KCl) was also used to elucidate by comparison the underlying mechanism of charge storage and to provide guidance for further optimisation.