Ultrasmall Co3O4 Nanoparticles Confined in P, N-Doped Carbon Matrices for High-Performance Supercapacitors

Co3O4 nanoparticles with smaller particle size can expose more active sites to react with electrolytes, thereby exhibiting better supercapacitive performance. However, the size of Co3O4 nanoparticles is difficult to be effectively controlled in traditional carbon matrices. Herein, P, N-codoped carbon matrices with ultrahigh surface area and abundant nanocavities are used as a novel host to confine the growth of Co3O4 nanoparticles. The Co3O4/carbon composites with high redox activities of Co3O4 are successfully obtained, in which Co3O4 nanoparticles are strongly anchored in the carbon matrices, resulting in the enhancement of the composites’ capacitive performance (1310 F g–1 at 0.5 A g–1). Meanwhile, the strong anchoring effect of the carbon host on Co3O4 nanoparticles because of the rich doping elements and the confinement effect of the nanocavities ensure long-term stability (92% capacitance retention after 5000 cycles). Furthermore, the assembled asymmetric supercapacitor using this composite as the cathode material and activated carbon as the anode material delivers a high energy density of 47.18 W h kg–1 at 375 W kg–1.