Novel Quaternary Chalcogenide/Reduced Graphene Oxide-Based Asymmetric Supercapacitor with High Energy Density

Mechanism study of the effect of copper ions on the stability of As(III) sulfuration precipitation in acidic copper smelting wastewater

Sulfide precipitation is considered as a very efficient method for removing arsenic from actual copper smelting acidic wastewater. However, the arsenic removal process can be affected by copper ions. This study focuses on the mechanism of copper ions' influence on the stability of As(III) sulfuration precipitation. Sulfuration reaction experiments are carried out using Na2S in three different simulated highly acidic wastewaters with initial As(III) concentrations of 2000 mg/L (LAs), 5000 mg/L (MAs), and 10000 mg/L (HAs), and the implications of processes variables of S/As ratio and copper concentration on the stability of As(III) sulfuration precipitation are discussed. The results show that the As(III) sulfuration precipitation is significantly affected by copper ions in the LAs reaction systems, whereas in the MAs and HAs reaction systems, which can be noticeably affected by copper ions only when the S/As is not greater than 1.5 (≤ 1.5), i.e., when the amount of Na2S is insufficient. Person correlation analysis also demonstrates a remarkable negative correlation (correlation coefficient is around - 0.96) between the S/As ratio and copper ion concentration on As(III) removal efficiency in the LAs reaction systems. The effect of copper ions on As2S3 is further investigated, and it is detected that copper ions cause approximately 3.3% of the precipitated As2S3 to be re-dissolved. This study proves that copper ions not only compete with As(III) for S2-, but also cause the precipitated As2S3 to re-dissolve. Therefore, in the actual manufacturing process, it is essential to control not only the sulfiding dose, but also the copper ions. This study provides a specific reference for actual enterprises to sulfurize As(III) from highly acidic wastewater and is of great significance for controlling actual industrial processes.

Construction of Nickel Molybdenum Sulfide/Black Phosphorous 3D Hierarchical Structure Toward High Performance Supercapacitor Electrodes

Supercapacitors (SCs) with outstanding versatility have a lot of potential applications in next-generation electronics. However, their practical uses are limited by their short working potential window and ultralow-specific capacity. Herein, the facile one-step in-situ hydrothermal synthesis is employed for the construction of a NiMo3S4/BP (black phosphorous) hybrid with a 3D hierarchical structure. After optimization, the NiMo3S4/BP hybrid displays a high specific capacitance of 830 F/g at 1 A/g compared to the pristine NiMo3S4 electrode. The fabricated NiMo3S4/BP//NiCo2S4/Ti3C2Tx asymmetric supercapacitor exhibits a better specific capacitance of 120 F/g at 0.5 A/g, which also demonstrates a high energy density of 54 Wh/kg at 1148.53 W/kg and good cycle stability with capacity retention of 86% and 97% of Coulombic efficiency after 6000 cycles. Further from the DFT simulations, the hybrid NiMo3S4/BP structure shows higher conductivity and quantum capacitance, which demonstrate greater charge storage capability, due to enhanced electronic states near the Fermi level. The lower diffusion energy barrier for the electrolyte K+ ions in the hybrid structure is facilitated by improved charge transfer performance for the hybrid NiMo3S4/BP. This work highlights the potential significance of hybrid nanoarchitectonics and compositional tunability as an emerging method for improving the charge storage capabilities of active electrodes.

Superior Visible Photoelectric Response with Au/Cu2NiSnS4 Core-Shell Nanocrystals

The incorporation of plasmonic metal nanostructures into semiconducting chalcogenides in the form of core-shell structures provides a promising approach to enhancing the performance of photodetectors. In this study, we combined Au nanoparticles with newly developed copper-based chalcogenides Cu2NiSnS4 (Au/CNTS) to achieve an ultrahigh optoelectronic response in the visible regime. The high-quality Au/CNTS core-shell nanocrystals (NCs) were synthesized by developing a unique colloidal hot-injection method, which allowed for excellent control over sizes, shapes, and elemental compositions. The as-synthesized Au/CNTS hybrid core-shell NCs exhibited enhanced optical absorption, carrier extraction efficiency, and improved photosensing performance owing to the plasmonic-induced resonance energy transfer effect of the Au core. This effect led to a significant increase in the carrier density of the Au/CNTS NCs, resulting in a measured responsivity of 1.2 × 103 AW-1, a specific detectivity of 6.2 × 1011 Jones, and an external quantum efficiency of 3.8 × 105 % at an incident power density of 318.5 μW cm-2. These results enlighten a new era in the development of plasmonic core-shell nanostructure-based visible photodetectors.

Two-dimensional MXenes: recent emerging applications

MXenes, are a rapidly growing family of two-dimensional materials exhibiting outstanding electronic, optical, mechanical, and thermal properties with versatile transition metal and surface chemistries. A wide range of transition metals and surface termination groups facilitate the properties of MXenes to be easily tuneable. Due to the physically strong and environmentally stable nature of MXenes, they have already had a strong presence in different fields, for instance energy storage, electrocatalysis, water purification, and chemical sensing. Some of the newly discovered applications of MXenes showed very promising results, however, they have not been covered in any review article. Therefore, in this review we comprehensively review the recent advancements of MXenes in various potential fields including energy conversion and storage, wearable flexible electronic devices, chemical detection, and biomedical engineering. We have also presented some of the most exciting prospects by combining MXenes with other materials and forming mixed dimensional high performance heterostructures based novel electronic devices.

Recent Advancements in Chalcogenides for Electrochemical Energy Storage Applications

Energy storage has become increasingly important as a study area in recent decades. A growing number of academics are focusing their attention on developing and researching innovative materials for use in energy storage systems to promote sustainable development goals. This is due to the finite supply of traditional energy sources, such as oil, coal, and natural gas, and escalating regional tensions. Because of these issues, sustainable renewable energy sources have been touted as an alternative to nonrenewable fuels. Deployment of renewable energy sources requires efficient and reliable energy storage devices due to their intermittent nature. High-performance electrochemical energy storage technologies with high power and energy densities are heralded to be the next-generation storage devices. Transition metal chalcogenides (TMCs) have sparked interest among electrode materials because of their intriguing electrochemical properties. Researchers have revealed a variety of modifications to improve their electrochemical performance in energy storage. However, a stronger link between the type of change and the resulting electrochemical performance is still desired. This review examines the synthesis of chalcogenides for electrochemical energy storage devices, their limitations, and the importance of the modification method, followed by a detailed discussion of several modification procedures and how they have helped to improve their electrochemical performance. We also discussed chalcogenides and their composites in batteries and supercapacitors applications. Furthermore, this review discusses the subject’s current challenges as well as potential future opportunities.

Marigold flower like structured Cu2NiSnS4 electrode for high energy asymmetric solid state supercapacitors

The growth in energy devices and the role of supercapacitors are increasingly important in today’s world. Designing an electrode material for supercapacitors using metals that have high performance, superior structure, are eco-friendly, inexpensive and highly abundant is essentially required for commercialization. In this point of view, quaternary chalcogenide Cu₂NiSnS₄ with fascinating marigold flower like microstructured electrodes are synthesized using different concentrations of citric acid (0, 0.05 M, 0.1 M and 0.2 M) by employing solvothermal method. The electrode materials physicochemical characteristics are deliberated in detail using the basic characterization techniques. The electrochemical studies revealed better electrochemical performances, in particular, Cu₂NiSnS₄@0.1 M-CA electrode revealed high 1029 F/g specific capacitance at 0.5 A/g current density. Further, it retained 78.65% capacity over 5000 cycles. To prove the practical applicability, a full-cell asymmetric solid-state device is fabricated, and it delivered 41.25 Wh/Kg and 750 Wh/Kg energy and power density at 0.5 A/g. The optimum citric acid added Cu₂NiSnS₄ electrode is shown to be a promising candidate for supercapacitor applications.

Zn Metal Atom Doping on the Surface Plane of One-Dimesional NiMoO4 Nanorods with Improved Redox Chemistry

The effect of zinc (Zn) doping and defect formation on the surface of nickel molybdate (NiMoO₄) structures with varying Zn content has been studied to produce one-dimensional electrodes and catalysts for electrochemical energy storage and ethanol oxidation, respectively. Zn-doped nickel molybdate (Ni_1-xZn_xMoO₄, where x = 0.1, 0.2, 0.4, and 0.6) nanorods were synthesized by a simple wet chemical route. The optimal amount of Zn is found to be around 0.25 above which the NiMoO₄ becomes unstable, resulting in poor electrochemical activity. This result agrees with our density functional theory calculations in which the thermodynamic stability reveals that Ni_1-xZn_xMoO₄ crystallized in the β-NiMoO₄ phase and is found to be stable for x≤0.25. Analytical techniques show direct evidence of the presence of Zn in the NiMoO₄ nanorods, which subtly alter the electrocatalytic activity. Compared with pristine NiMoO₄, Zn-doped NiMoO₄ with the optimized Zn content was tested as an electrode for an asymmetric supercapacitor and demonstrated an enhanced specific capacitance of 122 F g^-1 with a high specific energy density of 43 W h kg^-1 at a high power density of 384 W kg^-1. Our calculations suggest that the good conductivity from Zn doping is attributed to the formation of excess oxygen vacancies and dopants play an important role in enhancing the charge transfer between the surface and OH^- ions from the electrolyte. We report electrochemical testing, material characterization, and computational insights and demonstrate that the appropriate amount of Zn in NiMoO₄ can improve the storage capacity (∼15%) due to oxygen vacancy interactions.

Synthesis of single-phase CuCo2-xNixS4 for high-performance supercapacitors

Developing safe, efficient and environment-friendly energy storage systems continues to inspire researchers to synthesize new electrode materials. Doping or substituting host material by some guest elements has been regarded as an effective way to improve the performance of supercapacitors. In this work, single-phase CuCo_2-xNi_xS₄ materials were synthesized by a facile two-step hydrothermal method, where Co in CuCo₂S₄ was substituted by Ni. Cobalt could be easily substituted with Ni in a rational range to keep its constant phase. But, a high content of Ni resulted in a multi-phase composite. Among a series of CuCo_2-xNi_xS₄ materials with different Ni/Co mole ratios, CuCo_1.25Ni_0.75S₄ material presented a significantly high specific capacitance (647 F g^-1 or 272 C g^-1 at 1 A g^-1) and the best cycling stability (∼98% specific capacitance retention after 10,000 charge-discharge cycles), which was mainly due to the modified composition, specific single phase, higher electroconductivity, more electroactive sites and the synergistic effect between Ni and Co. Moreover, the assembled asymmetric capacitor using CuCo_1.25Ni_0.75S₄ as a positive electrode and activated carbon as a negative electrode delivered a high energy density of 31.8 Wh kg^-1 at the power density of 412.5 W kg^-1. These results demonstrated that ternary metal sulfides of CuCo_2-xNi_xS₄ are promising electrode materials for high-performance supercapacitors.

Applications of 2D MXenes in energy conversion and storage systems

This article provides a comprehensive review of MXene materials and their energy-related applications.

Growth and Self-Assembly of Silicon⁻Silicon Carbide Nanoparticles into Hybrid Worm-Like Nanostructures at the Silicon Wafer Surface

This work describes the growth of silicon⁻silicon carbide nanoparticles (Si⁻SiC) and their self-assembly into worm-like 1D hybrid nanostructures at the interface of graphene oxide/silicon wafer (GO/Si) under Ar atmosphere at 1000 °C. Depending on GO film thickness, spread silicon nanoparticles apparently develop on GO layers, or GO-embedded Si⁻SiC nanoparticles self-assembled into some-micrometers-long worm-like nanowires. It was found that the nanoarrays show that carbon⁻silicon-based nanowires (CSNW) are standing on the Si wafer. It was assumed that Si nanoparticles originated from melted Si at the Si wafer surface and GO-induced nucleation. Additionally, a mechanism for the formation of CSNW is proposed.

3D nanorhombus nickel nitride as stable and cost-effective counter electrodes for dye-sensitized solar cells and supercapacitor applications

Transition metal nitride based materials have attracted significant interest owing to their excellent properties and multiple applications in the field of electrochemical energy conversion and storage devices. Herein we synthesize 3D nanorhombus nickel nitride (Ni3N) thin films by adopting a reactive radio frequency magnetron sputtering process. The as-deposited 3D nano rhombus Ni3N thin films were utilized as cost-effective electrodes in the fabrication of supercapacitors (SCs) and dye-sensitized solar cells (DSSCs). The structure, phase formation, surface morphology and elemental composition of the as-deposited Ni3N thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and atomic force microscopy (AFM). The electrochemical supercapacitive performance of the Ni3N thin films was examined by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) techniques, in 3 M KOH supporting electrolyte. The areal capacitance of the Ni3N thin film electrode obtained from CV analysis was 319.5 mF cm-2 at a lower scan rate of 10 mV s-1. Meanwhile, the Ni3N thin film showed an excellent cyclic stability and retained 93.7% efficiency of its initial capacitance after 2000 cycles at 100 mV s-1. Interestingly, the DSSCs fabricated with a Ni3N CE showed a notable power energy conversion efficiency of 2.88% and remarkable stability. The prominent performance of the Ni3N thin film was ascribed mainly due to good conductivity, high electrochemically active sites with excellent 3D nano rhombus structures and high electrocatalytic activity. Overall, these results demonstrate that the Ni3N electrode is capable of being considered for efficient SCs and DSSCs. This investigation also offers an essential directive for the advancement of energy storage and conversion devices.

Flower-like Cu2NiSnS4 microspheres for application as electrodes of asymmetric supercapacitors endowed with high energy density

Asymmetric supercapacitors with superior specific capacitance and energy density are fabricated using Cu₂NiSnS₄, a novel and environmentally benign chalcogenide material.