Hierarchical carbon structures from soft drink for multi-functional energy applications of Li-ion battery, Na-ion battery and CO₂ capture

In this study, we report on the synthesis of a hierarchical carbon structure embedded with micro- and meso-pores through unique one-pot synthesis that synergistically integrates a hard-templating method using a KIT-6 template and an activation process using ZnCl₂ reagent. As a carbon source, we use soft drink that is rich in sugar and up-convert the industrial waste into a value-added product for a series of energy systems. Nitrogen adsorption results confirm that the optimized material with a hierarchical structure exhibits larger specific surface area (2003 m² g⁻¹) than that of material with only mesoporous structure (1813 m² g⁻¹), which is ascribed not only to the synergistic co-existence of micro- and meso-pores but also to the rigid structure without any collapse and fragmentation. Further increase of the activating reagent beyond the optimal point collapses the highly ordered mesoporous structure, which leads to only a limited surface area of 167 m² g⁻¹. The optimized hierarchical structure delivers promising functionalities in lithium ion and sodium ion batteries and CO₂ capture, which can be attributed to the unique hierarchical porous structure with high interconnectivity that facilitates alkali ions and gas diffusivities and accommodations. The observed performances of the present structure are superior to those of the mesoporous carbon structures, emphasizing the effectiveness of the unique methodology in designing highly multi-functional carbon materials.