Facile synthesis of hybrid CNTs/NiCo2S4 composite for high performance supercapacitors

Abstract

In this work, a novel carbon nanotubes (CNTs)/NiCo 2 S 4 composite for high performance supercapacitors was prepared via a simple chemical bath deposition combined with a post-anion exchange reaction. The morphologies and phase structures of the composites were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and low-temperature sorption of nitrogen (BET). The electro-chemical tests revealed that the CNT/NiCo 2 S 4 composite exhibited high electrochemical performance, because the CNTs were used as a conductive network for the NiCo 2 S 4 hexagonal nanoplates. Compared with pure NiCo 2 S 4 and the mechanically mixed CNTs/NiCo 2 S 4 composite, the CNTs/NiCo 2 S 4 composite electrode material exhibited excellent supercapacitive performance, such as a high specific capacitance up to 1537 F/g (discharge current density of 1 A/g) and an outstanding rate capability of 78.1% retention as the discharge current density increased to 100 A/g. It is therefore expected to be a promising alternative material in the area of energy storage.Supercapacitors have attracted considerable attentions because of their fast recharge capability, higher power density, and long cycling lifespan, all of which make them an essential power source for various energy storage applications 1-3 . In general, the electrode materials applied in supercapacitors can be divided into two categories based on their energy storage mechanisms: electrical double layer capacitors (EDLCs) and pseudo-capacitors (PCs) 3 . The performance of supercapacitors mainly depends on the electrochemical properties of the electrode materials. In fact, PCs usually exhibit much higher capacitances than EDLCs, because PCs electrode materials provide energy by fast and reversible redox reactions 4 .Transition metal sulphide (or oxide) exhibits ultra-high pseudoactive capacitance among the various electrode materials 5,6 , and has a much higher specific capacitance due to its multiple oxidation states. However, the poor electrical conductivity and low energy density of these materials restrict their applications 7 . Therefore, it is imperative to develop high performance alternative materials for supercapacitors.Recently, a type of ternary nickel cobalt sulphide (NiCo 2 S 4 ) has been demonstrated as a promising electrode material for supercapacitors. NiCo 2 S 4 has possess richer redox reactions than the corresponding binary nickel sulphide and cobalt sulphide 8 . Compared with NiCo 2 O 4 , NiCo 2 S 4 shows a narrower band gap and higher conductivity, which indicate better electrochemical performance 7,8 . Park et al. 9 . determined that the replacement of oxygen (O) with sulphur (S) creates a more flexible structure because the electronegativity of Sis lower than that of oxygen (O), which prevents the disintegration of the structure by the elongation between the layers followed by the enchancement of the electron transport efficiency in the structure. These advantages make NiCo 2...

Rechargeable Photoactive Zn‐Air Batteries Using NiCo2S4 as an Efficient Bifunctional Photocatalyst towards OER/ORR at the Cathode

“…The porous structure of the urchin‐like NiCo 2 S 4 microspheres was further confirmed by nitrogen adsorption‐desorption measurement. As shown in Figure S2a–b (Supporting Information), the adsorption‐desorption isotherms of NiCo 2 S 4 and NiCo 2 O 4 show a type‐IV and a type‐II isotherms, respectively with a remarkable hysteresis loop at relatively high pressure indicating their mesoporous characteristics . The specific surface area of the NiCo 2 S 4 is about 83 m 2 g −1 , which is larger than that of the NiCo 2 O 4 (ca.…”

Graphdiyne‐Supported NiCo2S4 Nanowires: A Highly Active and Stable 3D Bifunctional Electrode Material

“…The peaks at 1926.2 and 2189.8 cm −1 correspond to vibrations of the conjugated diyne links (CCCC). In the Raman spectra of NiCo 2 S 4 NW/GDF (Figure S4b, Supporting Information), the peaks of the GD were clearly observed at 1385.0, 1588.2, 1910.2, and 2179.3 cm −1 , corresponding to the D band, G band, and vibrations of the conjugated diyne links, respectively, whereas the peaks at 523.5 and 671.2 cm −1 correspond to the T 2g and A 1g modes of NiCo 2 S 4 . Moreover, the greatly enhanced intensity ratio of the D and G bands ( I D / I G ) for NiCo 2 S 4 NW/GDF (0.98 vs 0.78 of GDF) indicates a large increase of the structural defects, implying a significant increasing of active sites, which is beneficial to improvement of both OER and HER activities.…”

Facile synthesis of CoNi 2 S 4 /Co 9 S 8 composites as advanced electrode materials for supercapacitors

“…2b, Ni 2p spectrum can be fitted with two spin-orbit doublets and two shake-up satellites. As for Ni 2p spectrum, the binding energies situated at around 853.2 and 872.5 eV of the first doublet correspond to Ni 2+ and those at around 855.8 and 873.5 eV of the second doublet correspond to Ni 3+ [34][35][36]. Regarding to Co 2p spectrum (Fig.…”