Search

Transition metal sulfides (TMSs) are attractive anode materials for lithium-ion batteries (LIBs) due to their cost effectiveness, impressive redox properties, and high specific capacity. Among them, NiCo 2 S 4 stands out with a substantial theoretical capacity of 703 mAh g−1 and a high electronic conductivity of 1.25 × 106 S m−1, making it a strong candidate for LIBs. However, NiCo 2 S 4 experiences volume changes and mechanical stress during long-term cycling, leading to structural degradation and rapid capacity decay, which hinders its application. To address these issues, we have developed dodecahedral NiCo 2 S 4 embedded within a nitrogen-doped porous carbon structure (NiCo 2 S 4 /NC). The optimal NiCo 2 S 4 /NC-300 material exhibits minimum charge transfer resistance, maximum pseudo-capacitive contribution, and exceptional lithium storage performance. At 0.1 A g−1, NiCo 2 S 4 /NC-300 exhibits an initial discharge/charge specific capacity of 1730.1/949.4 mAh g−1 and retains a discharge capacity of 454.4 mAh g−1 after 100 cycles. Even at 0.5 A g−1, it delivers an initial discharge/charge capacity of 1301.1/540.1 mAh g−1 with a capacity retention of 81.2 % after 500 cycles. This study presents significant potential for NiCo 2 S 4 /NC as a high-performance anode material for LIBs, providing new strategies and insights into the mechanisms for enhancing the performance of TMS-based bimetallic anode materials. [ABSTRACT FROM AUTHOR]

Great efforts have been made to increase the hydrogen evolution reaction (HER) of electrocatalysts by porous structure, dopants and heterostructure engineering. However, the HER catalytic properties have entered a bottleneck stage only depend on these methods. As a contact-free field to enhance the electrochemical reactions, magnetic field has attracted extensive attention recently. In this study, the Ni-MOF derived NiCo 2 S 4 nanostructures are prepared via a facile hydrothermal preparation. By applying an external magnetic field, the NiCo 2 S 4 delivers much better HER performance than in normal condition (without magnetic field). An overpotentials of 104 mV and a Tafel slope of 54 mV·dec−1 are attained at 10 mA cm−2 in 1 M KOH under a moderated magnetic field of 100 mT, showing that the external magnetic field taking a positive effect to enhance the kinetic process of the NiCo 2 S 4 nanostructure. The presented results can offer an alternative strategy for further improving the HER property of electrocatalysis by utilizing an external magnetic field. [ABSTRACT FROM AUTHOR]

Sonication-supported hydrothermal process was used to synthesize nanoporous carbon composites of NiCo 2 S 4 @N−MWCNT and NiCo 2 S 4 @N−MWCNT/MOF67 for supercapacitor applications. The structural, morphological, and electrochemical properties of the synthesized composites were improved the use of the hydrothermal process. The composite electrodes were assembled via three-electrode configuration using 6 M KOH as electrolyte solution. The NiCo 2 S 4 @N−MWCNT and NiCo 2 S 4 @N−MWCNT/MOF-67 composites showed the specific capacitance of (254 and ∼455) F/g, respectively, at 1 A/g. Due to the incorporation of the metal organic framework nano porous structured composite, the increment of the specific capacitance was almost 1.78-fold. The electrode shows excellent capacitance retention of 98.43% and improved the cyclic stability in presence of 6 M KOH electrolyte. [ABSTRACT FROM AUTHOR]

Herein, we have developed a novel hybrid material based on NiCo 2 S 4 (NCS), halloysite nanotubes (HNTs), and carbon as promising electrodes for supercapacitors (SCs). Firstly, mesoporous NCS nanoflakes were prepared by co-precipitation method followed by physically mixing with HNTs and carbon, and screen printed on nickel foam. After ultrasonication, a uniform distribution of the Carbon/HNTs complex was observed, which was confirmed by surface morphological analysis. When used as electrode material, the NCS/HNTs/C hybrid displayed a maximum specific capacity of 544 mAh g−1 at a scan rate of 5 mV s−1. Later, a solid-state hybrid SCs was fabricated using activated carbon (AC) as the negative and NCS/HNTs/C as the positive electrode (NCS/HNTs/C//AC). The device delivers a high energy density of 42.66 Wh kg−1 at a power density of 8.36 kW kg−1. In addition, the device demonstrates long-term cycling stability. Furthermore, the optimized NCS, NCS/HNTs, and NCS/HNTs/C nanocomposites also presented superior hydrogen evolution reaction (HER) performance of 201, 169, and 116 mV in the acidic bath at a current density of 10 mA cm−2, respectively. Thus, the synthesis of NCS/HNTs/C nanocomposite as positive electrodes for hybrid SCs opens new opportunities for the development of next-generation high energy density SCs. [Display omitted] • Synthesis of novel hierarchical NiCo 2 S 4 nanoflakes using a simple co-precipitation method with high electrochemical performance. • Preparation of final NiCo 2 S 4 /HNTs/C composite electrode by screen-printing method on Ni foam. • Improved the supercapacitor capacitive properties than the NiCo 2 S 4 /HNTs/C then the NiCo 2 S 4 and NiCo 2 S 4 /HNTs composite. • A novel NiCo 2 S 4 /HNTs/C//AC constructed solid-state hybrid device. • SSHSc shows a high energy density of 42.66 Wh kg−1 at a power density of 8.36 kW kg−1. [ABSTRACT FROM AUTHOR]

The photoelectrochemical (PEC) process is one of the most promising techniques for converting solar energy directly into clean fuels and for environmental remediation applications. One-dimensional (1D) TiO 2 nanostructure arrays are extensively studied morphologies for a wide range of catalytic processes, including photocatalysis (PC) and PEC reactions for water splitting. In this study, a well-aligned spaced TiO 2 nanorod (TNR) arrays were uniformly grown on a fluorine-doped tin oxide (FTO) substrate, and thermal exfoliation of the TNRs, which appeared as small islands, was investigated. The calcination time, which ranged from 1 to 5 h at 400 °C, had a significant impact on the agglomerated TNRs islands, which tended to be uniformly exfoliated as spaced nanorods and eventually improved the PEC performance. The regularly arranged spaced nanorods allow for the efficient transfer of internal charge carriers within the TNRs. Furthermore, the heterojunction formation with NiCo 2 S 4 via the successive ionic layer adsorption and reaction (SILAR) method, substantially improve PEC performance, owing to reduced charge carrier recombination at the interface of the heterojunction. The Mott–Schottky analysis strongly supports the improved charge carrier density at the heterojunction interface. The improved life time of the charge carriers was investigated by comparing the time-resolved photoluminescence spectra for the TiO 2 /NiCo 2 S 4 heterojunction with pristine TNRs, which was eventually confirmed by incident photon-to-current efficiency analysis. [ABSTRACT FROM AUTHOR]

NiCo 2 S 4 is one of the most promising bimetallic sulfides for use in energy-storage systems, but more studies are needed to endow NiCo 2 S 4 with a high electrochemical reaction capability and reversibility. In this work, we present rationally materials design of an optimal NiCo 2 S 4 nanoparticle in a reduced graphene oxide (RGO) matrix as a NiCo 2 S 4 / RGO nanocomposite. Furthermore, we report the improvements in the materials technology, demonstrating the NiCo 2 S 4 / RGO nanocomposite electrode with an excellent specific capacitance of 963–700 F g−1 at 1–15 A g−1, high capacitance retention of 70%, and long cycle life of 3000 cycles. The practical application is showcased in an asymmetric supercapacitor with a high active-material loading. The NiCo 2 S 4 / RGO nanocomposite shows a high energy density of 31 Wh kg−1 at a power density of 987 W kg−1 and maintains an excellent density of 23 Wh kg−1 at a high power density of 7418 W kg−1. The outstanding electrochemical utilization and stability of the NiCo 2 S 4 / RGO nanocomposite confirm that our systematic optimization in the materials science and technology in terms of the active-material synthesis, the electrode development, and the device design/fabrication would benefit the future development of high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

In this study, dicobalt tetrasulfide (NiCo 2 S 4) nanoneedles were successfully synthesized by a two-step hydrothermal method on nickel foam. A layer of polypyrrole (PPy) was further wrapped on the surface of the NiCo 2 S 4 nanoneedles by in-situ polymerization. The obtained NiCo 2 S 4 @PPy composite was investigated for supercapacitor applications, which exhibited a capacitance of 1842.8 F g−1 at 1 A g−1. An asymmetric supercapacitor device fabricated with an activated carbon negative electrode and NiCo 2 S 4 @PPy positive electrodes exhibited an energy density of 41.2 Wh kg−1 at 402.2 W kg−1 with a high charge–discharge cycling stability (92.8% after 5000 cycles). These results demonstrate that NiCo 2 S 4 @PPy electrodes have broad application prospects as energy storage electrode materials. [ABSTRACT FROM AUTHOR]

To design and prepare novel composites with strong electrode structure and superior electrochemical performances via a facile and convenient synthesis method is a significant challenge to develop the high-performance materials for energy storage and conversion devices. Herein, we fabricated a novel hybridization of two dimensional (2D) Ti 3 C 2 -MXenes nanosheets and one dimensional (1D) nickel-cobalt sulfide (NiCo 2 S 4) hollow nanotubes though the favorable electrostatic interaction between the negatively charged Ti 3 C 2 and positively charged NiCo 2 S 4 nanotubes. The electrode combined the good metallic conductivity of Ti 3 C 2 -MXenes and high pseudo-capacitance of NiCo 2 S 4 demonstrated the outstanding electrochemical performance for supercapacitors. Herein, 2D Ti 3 C 2 -MXenes/1D NiCo 2 S 4 hybrid electrode achieved an excellent specific capacitance of 1927 F g-1 at 2 mV s-1, long cycling stability for 4000 cycles and charming rate performances, which is mainly ascribed to the synergistic effect and interfacial interaction between two components. Particularly, the novel hybrid material with 1D and 2D hierarchical structures can provide additional electrochemical reaction sites, supply shorter paths for ions diffusion and electron transport, and effectively raise the charge transfer kinetics during the electrochemical process, which explores a new strategy aimed to develop 2D Ti 3 C 2 -MXenes energy storage devices with high electrochemical performance, and is possible potential for expansion into other application fields. Image 1 [ABSTRACT FROM AUTHOR]

A novel Ti 3 C 2 @PDA/NiCo 2 S 4 composites as high performance supercapacitor electrodes were synthesized by the hydrothermal treatment process. The chemical modification and uniformly coating of Ti 3 C 2 surface by polydopamine (PDA) can prevent the structural collapse and over-oxidation of Ti 3 C 2 during the hydrothermal synthesis of NiCo 2 S 4. Furthermore, the confined-synthesis of smaller NiCo 2 S 4 particles between the Ti 3 C 2 layers, not only prevent the restacking of Ti 3 C 2 that between the adjacent monolayers during cycling, but also afford high surface areas accessible to charge transfer and ion diffusion. Thereby, enhance the electrochemical cycling stability of the Ti 3 C 2 @PDA/NiCo 2 S 4 composite. It is significant to explore how NiCo 2 S 4 alters the microstructure, morphology as well as supercapacitors performance of Ti 3 C 2 to tune the microstructure and performance of Ti 3 C 2 by appropriate hydrothermal synthesis strategy. The experimental results exhibit a prominent improvement in the supercapacitor performance, the gravimetric capacitance of Ti 3 C 2 @PDA/NiCo 2 S 4 composites achieve as high as 495 F g-1 at 2 mV s-1, which increase the 10 times as compared to the pristine Ti 3 C 2. Furthermore, the cycling stability of the Ti 3 C 2 @PDA/NiCo 2 S 4 composites electrode was enhanced significantly by the hierarchical architecture, and showed exceptional capacitance retention (81.16%) even after 3000 cycles. The dramatic improvement in the supercapacitors performance of Ti 3 C 2 @PDA/NiCo 2 S 4 electrodes is attributed to impressive conductive matrix Ti 3 C 2 , the effective modification of small size Ni 2 Co 2 S 4 , and the strong interfacial interaction between Ti 3 C 2 @PDA and NiCo 2 S 4. This study demonstrating its attractive application prospect of Ti 3 C 2 Mxenes modified with bimetallic sulfide as electrode materials for high-performance supercapacitors. Image 1 [ABSTRACT FROM AUTHOR]