Functionalized co-doped microporous carbon spheres for eco-friendly, high-performance and flexible supercapacitors

Abstract

Microporous carbon spheres co-doped with nitrogen and sulfur (NS-MCS) are synthesized by hydrothermal carbonization of glucose, pyrrole, and SDS. Interdigitated supercapacitors (IDE-SCs) are fabricated by integrating the NS-MCS with laser-induced graphene (LIG-IDEs). A significant enhancement in the electrocapacitive performance of the LIG-IDEs is accomplished upon integrating the NS-MCS ink, formulated using sodium alginate biopolymer. NS-MCS surface functionalization (FNS-MCS) leads to further enhancements in their electrocapacitive performance. Physicochemical analysis is conducted to investigate the whole profile of NS-MCS. DFT calculations are also conducted relying on the XPS results proposing two structures for the NS-MCS and FNS-MCS revealing that the inclusion of oxygen and nitrogen electronegative atoms besides less electronegative sulfur atoms to the NS-MCS surface creates highly polarized bonds with the carbon atoms accompanied by π-bonds delocalization which could provide multiple active centers for charge storage, facilitating charges mobility, thereby positively impacting the NS-MCS electrical and electrocapacitive performances. The fabricated IDE-SCs with FNS-MCS atop LIG could attain notable performance: specific areal capacitance of 47.03 F m− 2, high energy density of 5.4 mWh m− 2, and high-power density of 965.8 mW m− 2, surpassing bare LIG, besides excellent capacitance retention (106.65 %) after 5000 cycles, along with impressive flexibility proposing them for flexible and wearable electronics applications.