KCl-assisted activation of macadamia nut shell-derived carbon: Unveiling enhanced pore structure, adsorption and supercapacitor performance

A novel and efficient strategy, known as one-step pyrolysis with KCl-assisted K2C2O4 activation of biomass, was employed in the preparation of porous carbon derived from macadamia nut shells. Our aim was to analyze the alterations in material morphology and pore structure during the process of KCl-assisted activation. The addition of KCl during activation introduced additional mesopores and narrow micropores, resulting in a hierarchical pore structure. Compared to activation without KCl, the specific surface area increased by 50.7% and the pore content increased by 54.5%. We further investigated the evolution of the pore structure and activation mechanism during KCl-assisted activation. Among the tested samples, K3K5 showed the best adsorption performance with 6.48 and 4.11 mmol/g at 0 and 25 °C, respectively. In our study on the adsorption properties of CO2, we found that the narrow micropores are the primary factor influencing CO2 adsorption. Additionally, nonlinear fitting of adsorption isotherms indicated that the adsorption process followed a multilayer physisorption mechanism. We also explored the effects of KCl-assisted activation on the adsorption process. Furthermore, we evaluated the electrochemical properties of the activated carbon and determined that it functioned as a capacitance-controlled electric double-layer supercapacitor, with a specific capacitance of 279.3F/g at 0.5 A/g. We investigated the effects of KCl-assisted activation on specific capacitance, rate performance, and conductivity. This research provides valuable insights into the environmentally friendly synthesis of efficient CO2 adsorbents and energy storage materials.