Revealing the correlation of high-frequency performance of supercapacitors with doped nitrogen species

Nitrogen doping strategy has been widely used to enhance the performance of carbon electrodes in supercapacitors, particularly in terms of high-frequency response. However, the charge storage and ion response mechanisms of different nitrogen dopants at high frequencies are still unclear. In this study, we employ carbonized melamine foam with an open surface structure as a simplified model electrode material, enabling a comprehensive analysis of their impact on the ionic response behavior of high-frequency supercapacitors. Through a combination of experiments and first-principles calculations, we uncover that pyrrolic nitrogen, characterized by a higher adsorption energy, enhances the charge storage capacity of the electrode at high frequencies. On the other hand, graphitic nitrogen, with a lower adsorption energy, promotes rapid ion response. Furthermore, we propose the use of adsorption energy as a practical descriptor for electrode/electrolyte design in high-frequency applications, offering a more universal approach for optimizing the performance of N-doped carbon materials. This research contributes to the advancement of high-frequency supercapacitor technology and provides guidance for the development of improved N-doped carbon materials.