MnCo₂O₄@nitrogen-doped carbon nanofiber composites with meso-microporous structure for high-performance symmetric supercapacitors

The electrochemical properties of carbon nanofibers for supercapacitor application should be improved to meet the requirement of renewable energy systems. Herein we investigate the effect of MnCo₂O₄ on the electrochemical properties of carbon nanofibers. Nitrogen-doped carbon nanofibers incorporated with MnCo₂O₄ nanoparticles are synthesized by carbonizing manganese-cobalt@polyacrylonitrile nanofibers under N₂ atmosphere. The composite electrode-based symmetric supercapacitor at an optimum loading of 1/2 mmol has an excellent specific capacitance of 871.5 F g⁻¹ (at a current density of 0.5 A g⁻¹), presents an ultra-high energy density of 30.26 Wh kg⁻¹ and delivers an excellent cycle performance (retention rate of 89.3% after 5000 cycles). The outstanding electrochemical properties of composite electrode are mainly attributed to the doping of nitrogen and the introduction of MnCo₂O₄ into carbon matrix. The adoption of PAN is aimed to produce the doped nitrogen in carbon bulk, which can generate pseudocapacitance and improve the electrical conductivity of carbon nanofibers. The introduction of MnCo₂O₄ results in the formation of meso-microporous structure in CNFs, which facilitates the rapid and efficient transfer of charges into the electrode material. Besides, MnCo₂O₄ is an active material for pseudocapacitors that can undergo redox reaction during charge/discharge process, thus enhancing the electrochemical performance of carbon nanofibers.