Hierarchical Nickel–Cobalt Hydroxide Composite Nanosheets-Incorporated Nitrogen-Doped Carbon Nanotubes Embedded with Nickel–Cobalt Alloy Nanoparticles for Driving a 2 V Asymmetric Supercapacitor

Abstract

A class of electrode materials with favorable structures and compositions and powerful electrochemical (EC) properties are needed to boost the supercapacitor capacity significantly. In this study, an inventive technique was established to produce a well-aligned nickel-cobalt alloy nanoparticles-encapsulated N-doped carbon nanotubes with porous structure and good conductivity on carbon cloth (NiCo@NCNTs/CC) as a substrate. Then, nanosheets of nickel-cobalt layered double hydroxide (NiCo-LDH) were grown on NiCo@NCNTs/CC via a simple EC deposition method to construct a self-supported monolithic hierarchical nanosheets/nanotubes composite electrode of NiCo-LDH/NiCo@NCNTs/CC. In such a composite electrode, the NiCo@NCNTs can act as a good conductor and structural scaffold to grow NiCo-LDH nanosheets with a three-dimensional open and porous structure, which helps to improve the electron/ion-transfer performance, increase the number of exposed reactive sites, and inhibit the aggregation of NiCo-LDH nanosheets, thereby boosting the capacitance and stability. As a positive electrode, the NiCo-LDH/NiCo@NCNTs/CC hierarchical nanosheets/nanotubes electrode displays 1898 mF cm −2 (1262 A g −1 ) of high capacitance, long-term stability with a capacitance retention of around 100% after 8000 cycles, and nearly 103% Coulombic efficiency. After assembling into an asymmetric supercapacitor with a Co(OH) 2 / NiCo@NCNTs/CC negative electrode, 2 V of operating voltage with 73.1 μW h cm −2 (52.8 W h kg −1 ) of energy density was achieved. Our investigation gives a potential approach for constructing the integrated composite electrode of transition-metal compounds-carbon materials for high-performance supercapacitors.

Defective silicotungstic acid-loaded magnetic floral N-doped carbon microspheres for ultra-fast oxidative desulfurization of high sulfur liquid fuels

“…The peak at 291.4 eV corresponds to the O–CO bonds. 60,61 The high-resolution O1s spectrum given in Fig. 4c can be fitted into four peaks at 530.7 eV, 531.8 eV, 532.8 eV, and 534.0 eV corresponding to O–W–O linkage, oxygen vacancy (O v ), Si–O and O–C bonds, respectively.…”

“…The peak at 291.4 eV corresponds to the O-CvO bonds. 60,61 Fig. 3 (a-c) SEM images of γ-Fe 2 O 3 @NC@SiW 12 -300 at different magnifications; (d) SEM image and elemental mapping images of C, N, W, Fe, Si, and O; and (e) EDX spectra of γ-Fe 2 O 3 @NC@SiW 12 -300.…”

Recent advances in Ni-materials/carbon nanocomposites for supercapacitor electrodes

“…The electrochemical properties of supercapacitors on the basis of Ni materials and CNTs composite electrodes are reported in Table 2 144–163 The nanocomposite CNTs/NiCo 2 S 4 showed remarkable capacitive properties. In the structure of the asymmetric supercapacitor, it exhibited energy and power densities of 43.3 W h kg −1 and 800 W kg −1 .…”

“…Also, its usage in a supercapacitor with a Co(OH) 2 / NiCo@NCNTs/CC negative electrode led to 52.8 W h kg À1 of energy density. 155 Yuan et al 156 investigated a supercapacitor based on the Ni-Co-Se/C-CNTs electrode and achieved a specific capacitance of 1108.2 F g À1 . They mentioned the power and energy densities of Ni-Co-Se/C-CNTs//AC supercapacitors were 38.2 W h kg À1 and 1602.1 W kg À1 , respectively.…”

“…Ternary nickel cobalt sulfide/oxides and carbon nanotube composites. The electrochemical properties of supercapacitors on the basis of Ni materials and CNTs composite electrodes are reported in Table 2 [144][145][146][147][148][149][150][151][152][153][154][155][156][157][158][159][160][161][162][163] The nanocomposite CNTs/NiCo 2 S 4 showed remarkable capacitive properties. In the structure of the asymmetric supercapacitor, it exhibited energy and power densities of 43.3 W h kg À1 and 800 W kg À1 .…”