Mild modification of sponge-like carbon: Ammonia post-treatment for enhanced CO2 adsorption and suitability for supercapacitors

Abstract

During the synthesis of carbon-based CO2 adsorbents and supercapacitors, the introduction of nitrogen atoms into the carbon matrix has been identified as a means to enhance their performance. Nevertheless, the intricate effects of nitrogen doping on material properties pose a significant challenge in developing efficient methodologies. In this investigation, porous carbons resembling sponges were fabricated utilizing macadamia nut shells as a precursor and a dual salt comprising K2C2O4-KCl as an activating agent. Subsequent modification of the materials through ammonia post-treatment facilitated the production of nitrogen-doped porous carbon. The alterations in surface characteristics and pore morphology after ammonia treatment were meticulously examined to unravel the underlying mechanism of this modification process. The samples under scrutiny showcased remarkable CO2 adsorption capacities, peaking at 6.97 mmol/g at 0 °C and 4.65 mmol/g at 25 °C. Employing mathematical models to probe the influence of pore structure and surface properties on CO2 adsorption efficacy proved to be fruitful. A linear correlation was established to depict CO2 adsorption behavior, underscoring the joint impact of ultramicropore volume and nitrogen content on the adsorption process. Notably, the material exhibited a specific capacitance of 290.4F/g at a current density of 0.5 A/g within a three-electrode configuration, demonstrating commendable rate capability and cyclic stability. The pivotal findings from this inquiry emphasize that ammonia post-treatment represents a gentle modification strategy exerting minimal influence on the pore architecture, thereby efficaciously enhancing both CO2 adsorption and electrochemical performance.