Direct conversion of CO2 to meso/macro-porous frameworks of surface-microporous graphene for efficient asymmetrical supercapacitors

Abstract

CO₂ conversion to useful materials is the most attractive approach to control its content in the atmosphere. An ideal electrode material for supercapacitors should possess suitable meso/macro-pores as electrolyte reservoirs and rich micro-pores as places for the adsorption of electrolyte ions. Herein, we designed and synthesized such an ideal material, meso/macro-porous frameworks of surface-microporous graphene (MFSMG), from CO₂via its one-step exothermic reaction with potassium. Furthermore, the MFSMG electrode exhibited a high gravimetric capacitance of 178 F g⁻¹ at 0.2 A g⁻¹ in 2 M KOH and retained 85% capacitance after increasing current density by 50 times. The combination of the MFSMG electrode and the activated carbon (AC) electrode constructed an asymmetrical AC//MFSMG capacitor, leading to a high capacitance of 242.4 F g⁻¹ for MFSMG and 97.4 F g⁻¹ for AC. With the extended potential, the asymmetrical capacitor achieved an improved energy density of 9.43 W h kg⁻¹ and a power density of 3504 W kg⁻¹. This work provides a novel solution to solve the CO₂ issue and creates an efficient electrode material for supercapacitors.