The modification of MWCNTs with Prussian Blue (PB) represents a significant improvement of the energy density values of asymmetric carbon based supercapacitors (CBSCs) in neutral media (KCl). The development of the faradaic processes associated with the presence of PB on the positive electrode increases not only the capacitance but also the operational voltage of these devices (up to 1.4 V) due to the high electrode potentials at which the Prussian Blue/Berlin Green (PB/BG) redox reactions occur. Accordingly, in asymmetric CBSCs assembled using an activated carbon as negative electrode and MWCNTs as the positive one, suitable modification of MWCNTs with PB increases the energy density of the device fivefold (from 1.46 to 7.68 Wh kg(-1)). The resultant system becomes an asymmetric hybrid device in which the energy is stored due to the double layer formation in the negative electrode and the development of the PB faradaic processes in the positive electrode, which acts as a battery. (C) 2016 Elsevier Ltd. All rights reserved.