Supramolecular-mediated high nitrogen doping hierarchical porous carbon cathodes with multi-physi/chemisorption sites for Zn-ion hybrid supercapacitors

Enhancing Zn²⁺ storage necessitates the meticulous design of carbon-based cathodes with specific attributes, notably substantial nitrogen doping and high surface area. However, synthesizing materials that embody both advantages persists as a considerable obstacle. Herein, we introduce a strategy for synthesizing self-assembled supramolecular crystal framework carbonization-activated high nitrogen doping hierarchical porous carbon (H-NPC) with a specific surface area of 2202.96 m² g⁻¹ and a nitrogen doping level of 12.45 at.%, providing a plethora of physical and chemical adsorption sites for Zn²⁺ storage. The resulting H-NPC exhibits a notable capacity of 256.7 mAh g⁻¹ at 0.5 A g⁻¹, achieving a maximum energy density of 213 Wh kg⁻¹ at 450 W kg⁻¹ power density, alongside an extended service life with 91.4 % capacity retention over 10,000 cycles. Density functional theory calculations reveal the role of high nitrogen doping in enhancing the reversible adsorption/desorption of Zn²⁺, augmenting H-NPC's electrical conductivity, electron density at zincophilic active sites, and reducing the energy barrier for Zn²⁺ adsorption. This study emphasizes the crucial role of incorporating large specific surface areas and abundant nitrogen atoms into carbon electrodes with the aim of innovating high-efficiency aqueous zinc ion capacitor systems and provides a novel idea for designing new carbon-based materials.