Facile and binder-free synthesis of N-doped carbon/ZnCo2O4 hybrid nanostructures on nickel foam for high-performance solid-state asymmetric supercapacitor

A high-performance supercapacitor electrode was fabricated through a facile and binder-free hydrothermal method based on N-doped carbon/ZnCo2O4 honey nest nanostructures (N-C/ZnCo2O4). High-fructose corn syrup (HFCS55) was used as a new, green, and inexpensive carbon source. The structure and morphology of the electrode material were investigated using scanning electron microscopy (SEM) and Transmission electron microscopy (TEM), in addition to spectroscopic methods including X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) methods. XRD and FTIR methods confirmed the formation of N-C/ZnCo2O4 nanostructures. Moreover, electron microscopy showed that the nanoflakes of N-C/ZnCo2O4 with an average dimension of 22 nm formed on the electrode surface. Electrochemical studies revealed that the N-C/ZnCo2O4-based electrode maintains good electrochemical reversibility and excellent capacitive performance. A maximum specific capacitance of 1289 F g(- 1) at 3.5 A g(- 1) was obtained and supercapacitor maintained almost 86% of its initial capacitance after 2000 cycles. The electrochemical results showed that our electrode can be used as a promising electrode material for high-performance supercapacitor devices. A solid-state asymmetric supercapacitor (ASC) was fabricated using polyvinyl alcohol/KOH electrolyte, activated carbon, and N-C/ZnCo2O4 electrode. Our ASC device exhibited good electrochemical behavior with a high energy density of 41.9 Wh kg(- 1) and excellent capacitance retention (94%) after 2000 cycles.