Synthesis of copper sulfide nanowire arrays for high-performance supercapacitors

Recent achievements and performance of nanomaterials in microwave absorption and electromagnetic shielding

Due to the swift advancement of the electronic industry and information technology, electromagnetic wave absorption materials are gaining significance in the field of intelligent equipment and weaponry. Nanomaterials were developed to investigate wave absorbing materials that can achieve both impedance matching and attenuation balance. Nanomaterials possess the properties of being thin, lightweight, and capable of absorbing microwave radiation across a wide range of frequencies. This work aims to present a systematic overview of the recent advancements in core-shell materials, specifically carbon, oxide, and sulfide nanomaterials, with regards to their applications in electromagnetic absorption and electromagnetic shielding. This review intends to emphasize the core principles of electromagnetic interference (EMI) shielding and microwave absorption in different systems documented in the literature, along with diverse methods of synthesis and fabrication for creating effective wideband electromagnetic absorbers/shields. Lastly, we also endeavor to offer a comprehensive view and insight into the areas where future research will thrive. This study provides a comprehensive assessment of the current advancements in the field of microwave absorption and electromagnetic shielding of nanomaterials.

Mo4+-Doped CuS Nanosheet-Assembled Hollow Spheres for CO2 Electroreduction to Ethanol in a Flow Cell

Electrocatalytic CO2 reduction reaction (CO2RR) to ethanol has been widely researched for potential commercial application. However, it still faces limited selectivity at a large current density. Herein, Mo4+-doped CuS nanosheet-assembled hollow spheres are constructed to address this issue. Mo4+ ion doping modifies the local electronic environments and diversifies the binding sites of CuS, which increases the coverage of linear *COL and produces bridge *COB for subsequent *COL-*COH coupling toward ethanol production. The optimal Mo9.0%-CuS can electrocatalyze CO2 to ethanol with a faradaic efficiency of 67.5% and a partial current density of 186.5 mA cm-2 at -0.6 V in a flow cell. This work clarifies that doping high valence transition metal ions into Cu-based sulfides can regulate the coverage and configuration of related intermediates for ethanol production during the CO2RR in a flow cell.

Application of Copper-Sulfur Compound Electrode Materials in Supercapacitors

Supercapacitors (SCs) are a novel type of energy storage device that exhibit features such as a short charging time, a long service life, excellent temperature characteristics, energy saving, and environmental protection. The capacitance of SCs depends on the electrode materials. Currently, carbon-based materials, transition metal oxides/hydroxides, and conductive polymers are widely used as electrode materials. However, the low specific capacitance of carbon-based materials, high cost of transition metal oxides/hydroxides, and poor cycling performance of conductive polymers as electrodes limit their applications. Copper-sulfur compounds used as electrode materials exhibit excellent electrical conductivity, a wide voltage range, high specific capacitance, diverse structures, and abundant copper reserves, and have been widely studied in catalysis, sensors, supercapacitors, solar cells, and other fields. This review summarizes the application of copper-sulfur compounds in SCs, details the research directions and development strategies of copper-sulfur compounds in SCs, and analyses and summarizes the research hotspots and outlook, so as to provide a reference and guidance for the use of copper-sulfur compounds.

Tailoring the phase composition of carbon-coated nickel sulfides to achieve a high specific capacitance

As significant transition metal sulfides, nickel sulfides integrated with carbon were successfully synthesized in the presence of polyethylenimine and glutaraldehyde with a solvothermal route at 180 °C followed by carbonization. Glutaraldehyde prevented complete sulfur loss and allowed the formation of a mixed phase of nickel sulfide. The electrochemical performances of pure NiS2, NiS@C0, NiS2/NiS@C1, and NiS2/NiS@C2 electrodes were tested by a series of measurements. The specific capacitances obtained from GCD analysis were 698, 1160, 1484, and 908 F g-1 at 1 A g-1 for NiS2, NiS@C0, NiS2/NiS@C1, and NiS2/NiS@C2 electrodes, respectively. The results implied that the NiS2/NiS@C1 electrode possessed the highest specific capacitances and this study can be a good reference for the preparation of other hybrid metal sulfides as pseudocapacitive electrode materials.

The Facile Synthesis of Hollow CuS Microspheres Assembled from Nanosheets for Li-Ion Storage and Photocatalytic Applications

Herein, well-defined hollow CuS microspheres assembled from nanosheets were successfully synthesized through a facile solvothermal method. Hollow CuS microspheres have an average diameter of 1.5 μm; moreover, the primary CuS nanosheets have an ultrathin thickness of about 10 nm and are bound by {0001} polar facets. When used as anodes for lithium-ion batteries (LIBs), hollow CuS microspheres exhibit excellent electrochemical properties, including a large discharge capacity (610.1 mAh g^-1 at 0.5 C), an excellent rate capability (207.6 and 143.4 mAh g^-1 at 1 and 5 C), and a superior cyclic stability (196.3 mAh g^-1 at 1 C after 500 cycles). When used as photocatalysts for Rhodamine B (RhB), hollow CuS microspheres can degrade more than 99% of the initial RhB within 21 min. These excellent Li-ion storage properties and photocatalytical performances are attributed to their unique hierarchical hollow structure.

Copper (II) Heterocyclic Thiosemicarbazone Complexes as Single-Source Precursors for the Preparation of Cu9S5 Nanoparticles: Application in Photocatalytic Degradation of Methylene Blue

In this study, two copper(II) complexes, [Cu(C6H8N3S2)2]Cl2 (1) and [Cu(C7H10N3S2)2]Cl2·H2O (2), were synthesized from 2-(thiophen-2-ylmethylene)hydrazine-1-carbothioamide (L1H) and 2-(1-(thiophen-2-yl)ethylidene)hydrazine-1-carbothioamide (L2H) respectively and characterized using various spectroscopic techniques and elemental analyses. The as-prepared complexes were used as single-source precursors for the synthesis of oleylamine-capped (OLA@CuxSy), hexadecylamine-capped (HDA@CuxSy), and dodecylamine-capped (DDA@CuxSy) copper sulphide nanoparticles (NPs) via the thermolysis method at 190 °C and 230 °C and then characterized using powder X-ray diffraction (p-XRD), UV-visible spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The p-XRD diffraction patterns confirmed the formation of crystalline rhombohedral digenite Cu9S5 with the space group R-3m. The TEM images showed the formation of nanoparticles of various shapes including hexagonal, rectangular, cubic, truncated-triangular, and irregularly shaped Cu9S5 nanomaterials. The SEM results showed aggregates and clusters as well as the presence of pores on the surfaces of nanoparticles synthesized at 190 °C. The UV-visible spectroscopy revealed a general blue shift observed in the absorption band edge of the copper sulphide NPs, as compared to bulk CuxSy, with energy band gaps ranging from 2.52 to 3.00 eV. Energy-dispersive X-ray spectroscopy (EDX) confirmed the elemental composition of the Cu9S5 nanoparticles. The nanoparticles obtained at 190 °C and 230 °C were used as catalysts for the photocatalytic degradation of methylene blue (MB) under UV irradiation. Degradation rates varying from 47.1% to 80.0% were obtained after 90 min of exposure time using only 10 mg of the catalyst, indicating that Cu9S5 nanoparticles have potential in the degradation of organic pollutants (dyes).

Supercapacitor electrode materials: addressing challenges in mechanism and charge storage

In recent years, rapid technological advances have required the development of energy-related devices. In this regard, Supercapacitors (SCs) have been reported to be one of the most potential candidates to meet the demands of human’s sustainable development owing to their unique properties such as outstanding cycling life, safe operation, low processing cost, and high power density compared to the batteries. This review describes the concise aspects of SCs including charge-storage mechanisms and scientific principles design of SCs as well as energy-related performance. In addition, the most important performance parameters of SCs, such as the operating potential window, electrolyte, and full cell voltage, are reviewed. Researches on electrode materials are crucial to SCs because they play a pivotal role in the performance of SCs. This review outlines recent research progress of carbon-based materials, transition metal oxides, sulfides, hydroxides, MXenes, and metal nitrides. Finally, we give a brief outline of SCs’ strategic direction for future growth.

Enhanced Supercapacitor Performance and Electromagnetic Interference Shielding Effectiveness of CuS Quantum Dots Grown on Reduced Graphene Oxide Sheets

This study is focused on the preparation of the CuS/RGO nanocomposite via the hydrothermal method using GO and Cu-DTO complex as precursors. X-ray diffraction, Fourier-transform infrared spectroscopy, and Raman and X-ray photoelectron spectroscopy study revealed the formation of the CuS/RGO nanocomposite with improved crystallinity, defective nanostructure, and the presence of the residual functional group in the RGO sheet. The morphological study displayed the transformation of CuS from nanowire to quantum dots with the incorporation of RGO. The galvanostatic charge/discharge curve showed that the CuS/RGO nanocomposite (12 wt % Cu-DTO complex) has tremendous and outperforming specific capacitance of 3058 F g-1 at 1 A g-1 current density with moderate cycling stability (∼60.3% after 1000 cycles at 10 A g-1). The as-prepared nanocomposite revealed excellent improvement in specific capacitance, cycling stability, Warburg impedance, and interfacial charge transfer resistance compared to neat CuS. The fabricated nanocomposites were also investigated for their bulk DC electrical conductivity and EMI shielding ability. It was observed that the CuS/RGO nanocomposite (9 wt % Cu-DTO) exhibited a total electromagnetic shielding efficiency of 64 dB at 2.3 GHz following absorption as a dominant shielding mechanism. Such a performance is ascribed to the presence of interconnected networks and synergistic effects.

Copper sulfide nanostructures: easy synthesis, photocatalytic and doxorubicin anticancer drug delivery applications

Copper sulfide nanostructures with different morphologies were used as a photocatalyst and antitumor drug delivery.

Organic-Inorganic Complexation Chemistry-Mediated Synthesis of Bismuth-Manganese Bimetallic Oxide for Energy Storage Application

An organic-inorganic complexation method was applied for the synthesis of bismuth-manganese bimetallic oxide (BMO) nanoparticles where highly dispersed oxide particles were stabilized in an organic matrix (hexamethylenediamine). The as-synthesized hybrid material was subjected to microscopic, optical, and structural studies to gain comprehensive insights into the system. In the X-ray diffraction pattern, the majority of the diffracted peaks are matched to the orthorhombic phase of the Bi₃Mn₂O₇ structure. To extract the electrochemical property, the hybrid system was applied as an anode material and investigated for supercapacitive performance under alkaline conditions. The specific capacitance obtained was 612 F·g^-1 at the current density of 1 A·g^-1, and under the same current density, the energy density and power density achieved were 137.78 W·h·kg^-1 and 0.90 kW·kg^-1, respectively.

Giant Dielectric Constant of Copper Nanowires/Amorphous SiO2 Composite Thin Films for Supercapacitor Application

Transparent thin films comprising ultralong (within the range 52-387 μm) copper nanowires with diameter ∼7-9 nm encapsulated in amorphous silica have been successfully fabricated using an electrodeposition technique. The length and number density were controlled by electrodeposition time and concentration of precursor materials, respectively. Giant dielectric constant values (∼10¹⁰) obtained from these systems were quantitatively explained as a function of the length of the nanowires on the basis of quantum mechanical theory derived by Rice and Bernasconi. These transparent thin films offer a specific capacitance value of 550 F/g with more than 73% cyclic stability over a period of 900 cycles. Our findings demonstrate a facile pathway to control and improve the properties of metal nanowire-based transparent materials for use in supercapacitor applications.

Electrochemical Fingerprint of CuS-Hexagonal Chemistry from (Bis(N-1,4-Phenyl-N-(4-Morpholinedithiocarbamato) Copper(II) Complexes) as Photon Absorber in Quantum-Dot/Dye-Sensitised Solar Cells

The main deficit of quantum dot/dye-sensitised solar cells (QDSSCs) remains the absence of a photosensitiser that can absorb the entire visible spectrum and increase electrocatalytic activity by enhancing the conversion efficiency of QDSSCs. This placed great emphasis on the synthesis route adopted for the preparation of the sensitiser. Herein, we report the fabrication of hexagonal copper monosulfide (CuS) nanocrystals, both hexadecylamine (HDA) capped and uncapped, through thermal decomposition by thermogravimetric analysis (TGA) and a single-source precursor route. Morphological, structural, and electrochemical instruments were used to assert the properties of both materials. The CuS/HDA photosensitiser demonstrated an appropriate lifetime and electron transfer, while the electron back reaction of CuS lowered the electron lifetime in the QDSSCs. The higher electrocatalytic activity and interfacial resistance observed from current density-voltage (I–V) results agreed with electrochemical impedance spectroscopy (EIS) results for CuS/HDA. The successful fabrication of hexagonal CuS nanostructures of interesting conversion output suggested that both HDA capped and uncapped nanocrystals could be adopted in photovoltaic cells.

Development of Crystalline Cu2S Nanowires via a Direct Synthesis Process and Its Potential Applications

Large-scale and uniform copper(I) sulfide (Cu₂S) nanowires have been successfully synthesized via a cheap, fast, easily handled, and environmentally friendly approach. In addition to the reductive properties of the biomolecule-assisted method, they also have a strong shape- or size-directing functionality in the reaction process. The field-emission properties of the Cu₂S nanowires in a vacuum were studied by the Folwer–Nordheim (F–N) theory. The Cu₂S nanowires have a low turn-on field at 1.19 V/μm and a high enhancement factor (β) of 19,381. The photocatalytic degradation of Cu₂S nanowires was investigated by the change in the concentrations of rhodamine B (RhB) under UV illumination. These outstanding results of Cu₂S nanowires indicate that they will be developed as good candidates as electron field emitters and chemical photocatalysts in future nanoelectronic devices.

In-situ Functionalization of Metal Electrodes for Advanced Asymmetric Supercapacitors

Nanostructured metal-based compound electrodes with excellent electrochemical activity and electrical conductivity are promising for high-performance energy storage applications. In this paper, we report an asymmetric supercapacitor based on Ti and Cu coated vertical-aligned carbon nanotube electrodes on carbon cloth. The active material is achieved by in-situ functionalization using a high-temperature annealing process. Scanning and transmission electron microscopy and Raman spectroscopy confirm the detailed nanostructures and composition of the electrodes. The TiC@VCC and CuxS@VCC electrodes show a high specific capacity of 200.89 F g-1 and 228.37 F g-1, respectively, and good capacitive characteristics at different scan speeds. The excellent performance can be attributed to a large surface area to volume ratio and high electrical conductivity of the electrodes. Furthermore, an asymmetric supercapacitor is assembled with TiC@VCC as anode and CuxS@VCC as cathode. The full device can operate within the 0-1.4 V range, and shows a maximum energy density of 9.12 Wh kg-1 at a power density of 46.88 W kg-1. These findings suggest that the metal-based asymmetric electrodes have a great potential for supercapacitor applications.

A cabbage leaf like nanostructure of a NiS@ZnS composite on Ni foam with excellent electrochemical performance for supercapacitors

In the present study, a NiS@ZnS composite nanostructure was synthesized on a nickel foam substrate by a facile chemical bath deposition (CBD) method.

Electrodeposited Ni(OH)2-modified CuS core–shell-like hybrids as binder-free electrodes for high-performance supercapacitors

In this work, binder-free electrodes of CuS@Ni(OH)₂ were fabricated by hydrothermal and electrodeposition methods.

Hierarchical Cu2S nanorods with different crystal phases for asymmetrical supercapacitors and visible-light photocatalysis

Nanomaterials with hierarchical structures have attracted much attention recently due to their impressive behavior in many fields. Herein, hierarchical Cu2S nanorods with monoclinic and hexagonal phases are first in situ grown on copper sheets by simple hydrothermal methods. The solvent largely influences the feature of Cu2S nanorods during the growth process and the proposed mechanism is elaborately elucidated for these different Cu2S nanorods. Owing to their wheat-like architecture and higher electrical conductivity, the hexagonal Cu2S nanorods exhibit superior electrochemical performance with a specific capacitance of 346 mF cm-2 at 5 mA cm-2 and more than 90% capacitance after 2000 cycles. The solid-state asymmetrical supercapacitors based on the hexagonal Cu2S electrodes have a specific capacitance of 172 mF cm-2 at 5 mA cm-2 and excellent electrochemical stability with ∼90% capacitance after 2000 cycling tests. Moreover, the hierarchical Cu2S nanorods show great photocatalytic ability in the degradation of methylene blue (MB) and rhodamine B (RhB) dyes with the assistance of H2O2 under visible light. This work provides a way to fabricate copper sulfides with hierarchical structures and multi-functions.

Rational Design of Sulfur-Doped Copper Catalysts for the Selective Electroreduction of Carbon Dioxide to Formate

The selective electroreduction of CO₂ to formate (or formic acid) is of great interest in the field of renewable-energy utilization. In this work, we designed a sulfur-doped Cu₂ O-derived Cu catalyst and showed that the presence of sulfur can tune the selectivity of Cu significantly from the production of various CO₂ reduction products to almost exclusively formate. Sulfur is doped into the Cu catalysts by dipping the Cu substrates into ammonium polysulfide solutions. Catalyst films with the highest sulfur content of 2.7 at % showed the largest formate current density (jHCOO- ) of -13.9 mA cm^-2 at -0.9 V versus the reversible hydrogen electrode (RHE), which is approximately 46 times larger than that previously reported for Cu(110) surfaces. At -0.8 V versus RHE, the faradaic efficiency of formate was maintained at approximately 75 % for 12 h of continuous electrolysis. Through the analysis of the evolution of the jHCOO- and jH2 values with the sulfur content, we show that sulfur doping increases formate production and suppresses the hydrogen evolution reaction. Ag-S and Cu-Se catalysts did not exhibit any significant enhancement towards the reduction of CO₂ to formate. This demonstrates clearly that sulfur and copper acted synergistically to promote the selective formation of formate. A hypothesis about the role of sulfur is proposed and discussed.

Synthesis of nanostructured metal sulfides via a hydrothermal method and their use as an electrode material for supercapacitors

Metal sulfides have attracted considerable interest owing to their notable electrochemical properties and multiple application areas, such as solar cells and supercapacitors (SCs).

Diversified copper sulfide (Cu2-xS) micro-/nanostructures: a comprehensive review on synthesis, modifications and applications

As a significant metal chalcogenide, copper sulfide (Cu_2-xS, 0 < x < 1), with a unique semiconducting and nontoxic nature, has received significant attention over the past few decades. Extensive investigations have been employed to the various Cu_2-xS micro-/nanostructures owing to their excellent optoelectronic behavior, potential thermoelectric properties, and promising biomedical applications. As a result, micro-/nanostructured Cu_2-xS with well-controlled morphologies, sizes, crystalline phases, and compositions have been rationally synthesized and applied in the fields of photocatalysis, energy conversion, in vitro biosensing, and in vivo imaging and therapy. However, a comprehensive review on diversified Cu_2-xS micro-/nanostructures is still lacking; therefore, there is an imperative need to thoroughly highlight the new advances made in function-directed Cu_2-xS-based nanocomposites. In this review, we have summarized the important progress made in the diversified Cu_2-xS micro-/nanostructures, including that in the synthetic strategies for the preparation of 0D, 1D, 2D, and 3D micro-/nanostructures (including polyhedral, hierarchical, hollow architectures, and superlattices) and in the development of modified Cu_2-xS-based composites for enhanced performance, as well as their various applications. Furthermore, the present issues and promising research directions are briefly discussed.

Compound Copper Chalcogenide Nanocrystals

This review captures the synthesis, assembly, properties, and applications of copper chalcogenide NCs, which have achieved significant research interest in the last decade due to their compositional and structural versatility. The outstanding functional properties of these materials stems from the relationship between their band structure and defect concentration, including charge carrier concentration and electronic conductivity character, which consequently affects their optoelectronic, optical, and plasmonic properties. This, combined with several metastable crystal phases and stoichiometries and the low energy of formation of defects, makes the reproducible synthesis of these materials, with tunable parameters, remarkable. Further to this, the review captures the progress of the hierarchical assembly of these NCs, which bridges the link between their discrete and collective properties. Their ubiquitous application set has cross-cut energy conversion (photovoltaics, photocatalysis, thermoelectrics), energy storage (lithium-ion batteries, hydrogen generation), emissive materials (plasmonics, LEDs, biolabelling), sensors (electrochemical, biochemical), biomedical devices (magnetic resonance imaging, X-ray computer tomography), and medical therapies (photochemothermal therapies, immunotherapy, radiotherapy, and drug delivery). The confluence of advances in the synthesis, assembly, and application of these NCs in the past decade has the potential to significantly impact society, both economically and environmentally.

Enhanced Electrochemical and Photocatalytic Performance of Core-Shell CuS@Carbon Quantum Dots@Carbon Hollow Nanospheres

A controlled structural morphology, high specific surface area, large void space, and excellent biocompatibility are typical favorable properties in electrochemical energy storage and photocatalytic studies; however, a complete understanding about this essential topic still remains a great challenge. Herein, we have developed a new type of functionalized carbon hollow-structured nanospheres based on core-shell copper sulfide@carbon quantum dots (CQDs)@carbon hollow nanosphere (CHNS) architecture. This CuS@CQDs@C HNS is accomplished by a simple, scalable, in situ single-step hydrothermal method to produce the material that can be employed as an electrode for electrochemical energy storage and photocatalytic applications. Impressively, the CuS@CQDs@C HNS nanostructure delivers exceptional electrochemical energy storage characteristics with high specific capacitance (618 F g^-1 at a current density of 1 A g^-1) and an excellent rate capability with an extraordinary capacitance (462 F g^-1 at current density of 20 A g^-1) and long cycle life (95% capacitance retention after 4000 cycles). Further, the proposed photocatalyst exhibited superior photocatalytic activity under solar light due to the efficient electron transfer, which was revealed by photoluminescence studies. Such superior electrochemical and photocatalytic performance can be ascribed to the mutual contribution of CuS, CQDs, and CHNS and unique core-shell architecture. These results exhibit that the core-shell CuS@CQDs@C HNS nanostructure is one of the potential candidates for supercapacitors and photocatalytic applications.