Intrinsically active capsaicin non-covalently modified nitrogen doped graphene for high-performance supercapacitors

Organic molecules with multi-electron redox active centers exhibit great potential in electrochemical storage. Immobilizing them on the graphene surface through pi-pi interaction can effectively improve the pseudocapac-itance. Nature capsaicin (Cap) molecule, with redox active sites, is good benefit for enhance the capacitance performance of the nitrogen doped graphene (NG) by non-covalent modification. In this work, the Cap-func-tionalized NG (Cap-NG) is successfully prepared by one-step hydrothermal method combined with vacuum freeze-drying technology. The electrochemical measurements show that the optimal Cap-NG exhibits a high capacitance of 312 F g-1 at 1 Ag-1 and an excellent durable cycling life of 102.9 % after 10,000 charging/dis-charging cycle times at a current density of 20 Ag-1. Furthermore, the Cap-NG-based symmetrical supercapac-itor (SSC) demonstrates an energy density of 8 Wh kg-1 at 596 W kg-1. Moreover, density functional theory (DFT) calculations are used to elaborate the origin of pseudocapacitance by researching the adsorption config-uration, binding energy and charge storage mechanism of Cap on NG sheet as well as to calculate the density of states (Dos). This study further enriches the application of natural capsaicin molecule on energy storage, and provides another way to build a green and environment-friendly SCs.