Direct Growth of Oxygen Vacancy-Enriched Co₃O₄ Nanosheets on Carbon Nanotubes for High-Performance Supercapacitors

Ultrathin Co 3 O 4 nanosheets (NSs) with abundant oxygen vacancies on conductive carbon nanotube (CNT) nanocomposites (termed as Co 3 O 4 -NSs/CNTs) are easily achieved by an effective NaBH 4 -assisted cyanogel hydrolysis strategy under ambient conditions. The specific capacitance of Co 3 O 4 -NSs/CNTs with 5% CNT mass can reach 1280.4 F g –1 at 1 A g –1 and retain 112.5% even after 10 000 cycles, demonstrating very high electrochemical capability and stability. When assembled in the two-electrode Co 3 O 4 -NSs/CNTs-5%//reduced graphene oxide (rGO) system, a maximum specific energy density of 37.2 Wh kg –1 (160.2 W kg –1 ) is obtained at room temperature. Ultrathin structure of nanosheets, abundant oxygen vacancies, and the synergistic effect between Co 3 O 4 -NSs and CNTs are crucial factors for excellent electrochemical performance. Specifically, these characteristics favor rapid electron transfer, complete exposure of the active interface, and sufficient adsorption/desorption of electrolyte ions within the active material. This work gives insights into the efficient construction of two-dimensional hybrid electrodes with high performance for the new-generation energy storage system.