Electrosorption behavior of cations with carbon nanotubes and carbon nanofibres composite film electrodes

The cost-effective, large area carbon nanotubes and carbon nanofibres (CNTs–CNFs) composite film was synthesized on graphite substrate by low pressure and low temperature thermal chemical vapor deposition. Cyclic voltammetry and ac impedance spectroscopy were employed to systematically study the electrochemical properties of CNTs–CNFs film. The electrosorption in salt solutions by CNTs–CNFs film electrodes was studied. It is found that electrosorption of CNTs–CNFs film electrodes is mainly due to Coulombic interaction on the electrical double-layer. Several experiments were conducted to study the ion removal capacity and selectivity of CNTs–CNFs film electrodes, showing that multivalent cations were preferentially adsorbed from the aqueous solution. For cations with same charge, the one with smaller hydrated radius would be more effectively removed.