Selective Nitrogen Doping at Hole Edges of Holey Graphene: Enhancing Ionic Transport Mechanisms for High‐Performance Supercapacitors

Developing highly holey graphene with controllable doping enhances ionic transport and conductivity, boosting the performance of energy storage devices like supercapacitors. However, the method for precise site-selective doping and the effects of heterogeneous atomic doping at pore edges on ion transport remain not fully understood. This study presents a method to achieve precisely and selectively high nitrogen doping (N-doping) at the hole edges of porous graphene (N-EHG) through a two-step process. Compared to untreated graphene (HG) and basal plane-doped graphene (N-BHG), N-EHG demonstrates superior charge storage capacity and ionic conductivity. Analyzing the porous structure, size distribution, and hydrophilicity influenced by the carbon-oxygen ratio, N-EHG shows a specific surface area of 509 m² g^-1, significantly higher than HG's 100 m² g^-1. Electrochemical results revealed that N-BHG and N-EHG achieved high gravimetric capacitances of 482.3 and 624.4 F g^-1, respectively, due to enhanced ion diffusion, exceeding HG by ≈12- and 15.6-fold. Furthermore, the assembled coin-cell retains over 99% capacitance after 15,000 cycles, demonstrating exceptional stability. Both N-EHG and N-BHG show diffusion-governed charge storage, with N-EHG benefitting further from edge-state N-doping. Density Functional Theory (DFT) calculations reveal a lower energy barrier for ion diffusion and strong K⁺ adsorption on edge pyridinic-N, where increased electrode charge creates a negative center on N-dopants, enhancing K⁺ binding. These findings underscore the potential of edge-state N-doping in holey graphene for advanced energy storage applications.