Linoleic Acid-Derived Carbon Microspheres with Hierarchical Porous Structure and Controllable Surface Groups toward Application in Supercapacitors

Hierarchical porous carbons (HPCs) with optimized porosity and enriched surface functional groups are a promising carbon material for supercapacitor development. However, it is a challenge to realize the selective regulation of surface functional groups. In this study, the HPCs with enriched carbonyl (CO) and carboxyl (O–CO) groups were prepared from linoleic acid by using the carbonization under autogenic pressure at elevated temperatures (CAPET) method followed by KOH activation. In the CAPET process, no liquid phase was generated and the yields of carbonized particles and combustible gas were about 43 and 57%, respectively, at 600 °C. After KOH activation, the activated HPCs possess enriched microporous and mesoporous channels and the high specific surface area (SSA) of 1992–2414 m2 g–1 was generally obtained for HPCs-600, HPCs-700, and HPCs-800. The maximum SSA was obtained in HPCs-600, whereas the higher faction of the mesopore structure was found in the HPCs with a higher activation temperature, e.g., V meso/V total of 53.3% in HPCs-800. When acting as an electrode material in supercapacitors, HPCs-700 displayed an outstanding electrochemical performance and cycling stability, i.e., a specific capacitance of 365 F g–1 at a current density of 0.5 A g–1 in KOH electrolyte. This study provides great insights into the structure design of HPCs and the smart resource utilization of waste cooking oil into valuable products.