Nitrogen doped and porous carbons towards new energy storage mechanisms for supercapacitors with high energy density Supercapacitors are electrochemical energy storage devices with rapid charge discharge rate and long cycle life. Their biggest challenge is the inferior energy density compared to other electrochemical energy storage devices such as batteries. Being the most widely spread type of supercapacitors electrochemical double layer capacitors (EDLCs) store energy by electrosorption of electrolyte ions on the surface of charged electrodes. As a more recent development Na ion capacitors (NICs) are expected to be a more promising tactic to tackle the inferior energy density due to their higher capacity electrodes and larger operating voltage. The charges are simultaneously stored by ion adsorption on the capacitive type cathode surface and via faradic process in the battery type anode respectively. Porous carbon electrodes are of great importance in these devices but the paramount problems are the facile synthetic routes for high performance carbons and the lack of fundamental understanding of the energy storage mechanisms. [...]