Lignite-based nanoarchitectonics with N self-doped and oxygen-rich hierarchically porous activated carbons for high performance supercapacitors

In the context of the 'dual carbon' initiative, coal remains a crucial primary energy source, and its clean utilization and value enhancement are imperative for future research and development. This study explored the influence of activation temperature, activation time, impregnation time, and the NaOH-to-coal mass ratio on the morphological and electrochemical properties of lignite-derived activated carbon through single-factor and response surface methodology experiments. Optimal activation conditions were determined: an activation temperature of 801 degrees C, an impregnation time of 24.7 h, an activation time of 1.1 h, and a NaOH-to-coal mass ratio of 7.2:1. Under these conditions, the resulting lignite-based activated carbon exhibited a high specific surface area of 2415.9 m2 g- 1. Electrochemical evaluations in a three-electrode system revealed a specific capacitance of 321.7 F g- 1 at a current density of 1 A g- 1. After 10,000 cycles at 10 A g- 1, the capacitance retention rate remained high at 98.1 %. Moreover, the performance of the lignite-based activated carbon, activated using sodium hydroxide, was comparable to that of materials activated with potassium hydroxide, as reported in literature. The NaOH-optimized lignite-based activated carbon electrode is an exemplary material for the commercialization of supercapacitors.