Regulation of Pyrrolic N in Grapevine-Based Ultrahigh Microporosity Activated Hydrochar Materials for Supercapacitors

Recently, significant progress has been made in the application of biomass in the field of supercapacitors, particularly in the development of high-performance electrode materials, which shows great potential and promise. Despite these advancements, the impact of specific surface area and pyrrolic nitrogen content on the final material performance remains inconclusive. The study underscores the pivotal role of nitrogen morphology in the nitrogen doping process, particularly highlighting the relationship between electrical properties and pyrrolic nitrogen content. Notably, when both the nitrogen doping content and the specific surface area increase concurrently, the electrical properties and pyrrolic nitrogen content exhibit a consistent “volcano-like” transition. Building on these insights, a porous nitrogen-containing carbon material, PCH-G-CR₂, was synthesized. This material is characterized by a medium specific surface area, a high pyrrolic nitrogen content, and a rich microporous structure. In a three-electrode system, it demonstrates a specific capacitance of up to 551.25 F/g at a current density of 0.5 A/g. Moreover, its symmetrical device attained an energy density of 45.92 Wh/kg and a power density of 0.5 kW/kg. Notably, the capacity retention rate was 83.44% after 30,000 cycles at a high current density of 10 A/g. This study proposes an eco-friendly and efficient method for preparing biomass-based porous hydrothermal carbon materials suitable for high-performance supercapacitors.