ZIF-67 derived Co3S4 hollow microspheres and WS2 nanorods as a hybrid electrode material for flexible 2V solid-state supercapacitor

Zeolitic imidazolate framework-67-derived chalcogenides as electrode materials for supercapacitors

With the rapid development of new energy technologies, hybrid supercapacitors have received widespread attention owing to their advantages of high power density, fast charging/discharging rate and long cycle life. In this case, the selection and design of electrode materials are the key to improving the energy storage performance of supercapacitors. Herein, zeolitic imidazolate framework-67 (ZIF-67) is presented as a good candidate material for the fabrication of supercapacitor electrodes because of its controllable pore size, constant cavity size and large specific area. Moreover, pristine ZIF-67 and ZIF-67-derived porous carbon have shown exemplary performances in supercapacitors. However, they belong to the class of electric double layer capacitor materials and have a lower magnitude of energy storage compared with pseudocapacitor materials. Therefore, to improve the energy density of hybrid supercapacitors, other ZIF-67 derivatives need to be explored, especially chalcogenides. This review mainly reports the application of ZIF-67-derived transition metal chalcogenides (TMCs, C including Oxide, Sulfide, Selenide, Telluride) in supercapacitors. Moreover, the strategies for the preparation of ZIF-67-derived TMCs and their electrochemical performance in supercapacitors are further discussed. Finally, the remaining challenges and future perspectives are highlighted.

Label-free electrochemical immunoassay for ultra-sensitive detection of PSA utilizing gold nanoparticles/polyhedral hollow CoCu bimetallic sulfide nanostructure as a dual signal amplification platform

This study introduces the development of a highly sensitive label-free electrochemical immunosensor specifically designed to detect prostate-specific antigen (PSA). A glassy carbon electrode (GCE) coated with Au nanoparticles/polyhedral hollow CoCu bimetallic sulfide (CuCo2S4) was employed as a sensing interface for the fixation of the monoclonal anti-PSA antibody. The nanoarchitectures enhanced the capacity for loading prostate-specific antibodies (Ab) and effectually boosted electrical conductivity leading to enhance the electrochemical signal and greater sensitivity for the detection of PSA. The electrochemical behavior of the engineered sensor was researched via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The response of the fabricated immunosensor manifested a linearized correlation with PSA concentration, spanning from 50.0 fg/ml to 500.0 ng/ml, with a minimal detection limit (DPV: 19.0 fg/ml, EIS: 14.0 fg/ml) and superior stability. The morphological and structural features of the engineered nanomaterials were analyzed using a range of techniques, including field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The proposed immunosensor was utilized for the meticulous and ultra-sensitive analysis of PSA levels in serum specimens, providing results that align satisfactorily with those from the enzyme-linked immunosorbent assay (ELISA) the benchmark protocol. In conclusion, these outcomes underscore the potential utility of the developed immunosensor for prostate cancer screening in its initial stages.

High performance supercapacitors driven by the synergy of a redox-active electrolyte and core-nanoshell zeolitic imidazolate frameworks

The selection of appropriate electrolytes plays a crucial role in improving the electrochemical performance of the supercapacitor electrode. The electrolyte helps to select an appropriate potential window of the device, which is directly related to its energy density. Also, the selection of an appropriate electrode material targets the specific capacitance. Therefore, in this work, we targeted an electrode material based on a ZIF-8@ZIF-67 (Z867) core-nanoshell structure and tested its performance in redox active electrolyte (RAE), i.e., 0.2 M K3[Fe(CN)6] in 1 M Na2SO4. The synergy between the core-nanoshell electrode having ZIF-8 as a core and ZIF-67 as a nanoshell along with RAE further complements the redox active sites, resulting in the improved charge transport. Therefore, when the Z867 core-nanoshell electrode is tested in a three-electrode system, it outperforms pristine ZIF-8 and ZIF-67 electrode materials. The working electrode modified with the Z867 core-nanoshell showed a maximum specific capacitance of 496.4 F g-1 at 4.5 A g-1 current density with the RAE, which is much higher than that of the aqueous electrolyte. A Z867-modified working electrode was assembled as the positive and negative electrode in a symmetrical cell configuration to create a redox supercapacitor device for practical application. The constructed device displayed maximal energy and power densities of 49.6 W h kg-1 and 3.2 kW kg-1 respectively, along with a capacitance retention of 92% after 10 000 charge-discharge cycles. Hence, these studies confirm that using RAE can improve the electrochemical performance of electrodes to a greater extent than that of aqueous electrolyte-based supercapacitors.

A Comparison of the Electrical Properties of Gel Polymer Electrolyte-Based Supercapacitors: A Review of Advances in Electrolyte Materials

Flexible solid-state-based supercapacitors are in demand for the soft components used in electronics. The increased attention paid toward solid-state electrolytes could be due to their advantages, including no leakage, special separators, and improved safety. Gel polymer electrolytes (GPEs) are preferred in the energy storage field, likely owing to their safety, lack of leakage, and compatibility with various separators as well as their higher ionic conductivity (IC) than traditional solid electrolytes. This review covers the classification, properties, and configurations of different GPE-based supercapacitors and recent advancements that have occurred in this area of energy storage. Ionic liquid (IL)-based materials are popular GPEs for electrochemical energy storage and can be used to prepare unprecedented flexible supercapacitors due to their great IC and wide potential range. A comparative assessment of the GPEs-based supercapacitors reveals that in a majority of them, the value of specific capacitance is generally under 1000 F g-1, energy density reaches around 125 Wh kg-1, and the power density is seen to be less than 1500 W kg-1. The results of this research serve as an essential reference for upcoming scholars, and could significantly improve our comprehension of the efficacy of GPE-containing supercapacitors.

Synthesis of Co/Co3O4 Heterostructure in N-Doped Porous, Amorphous Carbon: A Superior Electrochemical Sensor for Sensitive Determination of Alectinib in Various Fluids

Highly crystallized Co and Co3O4 nanoparticles embedded in an N-doped amorphous carbon matrix have been successfully fabricated by the molten-salt-assisted method using KClO3 and zeolitic imidazolate framework-12 (ZIF-12). Pyrolysis of ZIF-12 with different concentrations of KClO3 leads to embedded Co and Co3O4 nanoparticles in a conductive amorphous carbon network. The impact of salt concentration on the morphology and electrochemical performance of these composites was investigated for electrochemical sensor applications. By employing a straightforward and efficient technique, Co/Co3O4 heterostructures were successfully synthesized in N-doped porous amorphous carbon. The Co/Co3O4 carbon heterostructures were optimized by varying the salt concentration, resulting in a significant electrochemical sensor performance for detecting ALC in both bulk and biological fluids. The sensor demonstrates excellent sensitivity (62.97 nmol/L) and selectivity toward ALC, with a wide linear range (0.2-2 μM) and a low detection limit (18.89 nM). Furthermore, it displays remarkable stability and reproducibility, positioning it as a strong contender for practical use in pharmaceutical analysis and biomedical research. This study presents a significant advancement in electrochemical sensing technology and underscores the potential of Co/Co3O4 heterostructures in the development of high-performance sensors for detecting bioactive compounds in complex matrices.

Construction of hierarchical MOF-derived CoS2 microsheet arrays@NiMo2S4 nanoflakes on Ni foam as a high-performance supercapacitor electrode

The reasonable design of electrode material composition and structure is an effective way to solve the low energy density of supercapacitors. In this paper, hierarchical MOF-derived CoS2 microsheet arrays@NiMo2S4 nanoflakes on Ni foam (CoS2@NiMo2S4/NF) was prepared by the co-precipitation, electrodeposition and sulfurization process. MOF-derived CoS2 microsheet arrays on NF are used as ideal backbones to provide fast transport channels, and NiMo2S4 nanoflakes with a network-like distribution on the CoS2 microsheet arrays can improve the accessible active sites and promote the penetration and transfer of electrolyte ions. Due to the synergistic effects between the multi components, CoS2@NiMo2S4 exhibits excellent electrochemical properties. The specific capacity of CoS2@NiMo2S4 is 802 C g-1 at 1 A g-1. Hybrid supercapacitor assembled by CoS2@NiMo2S4 and activated carbon exhibits an energy density of 32.1 Wh kg-1 at a power density of 1130.3 W kg-1 and a cycle stability of 87.2% after 10, 000 cycles. This confirms the great potential of CoS2@NiMo2S4 as a supercapacitor electrode material.

Synergistic 2D MoSe2@WSe2 nanohybrid heterostructure toward superior hydrogen evolution and flexible supercapacitor

Two-dimensional (2D) transition metal dichalcogenide (TMDC) heterostructure is a new age strategy to achieve high electrocatalytic activity and ion storage capacity. The less complex and cost-effective applicability of the large-area TMDC heterostructure (HS) for energy applications require more research. Herein, we report the MoSe₂@WSe₂ nanohybrid HS electrocatalyst prepared using liquid exfoliated nanocrystals, followed by direct electrophoretic deposition (EPD). The improved catalytic activity is attributed to the exposure of catalytic active sites on the edge of nanocrystals after liquid exfoliation and the synergistic effect arises at HS interfaces between the MoSe₂ and WSe₂ nanocrystals. As predicted, the HS catalyst achieves a lower overpotential of 158 mV, a smaller Tafel slope of 46 mV dec^-1 for a current density of 10 mA cm^-2, and is stable for a long time. The flexible symmetric supercapacitor (FSSC) based on the HS catalyst demonstrates the excellent specific capacitance (C_sp) of 401 F g^-1 at 1 A g^-1, 97.20% capacitance retention after 5000 cycles and high flexible stability over 1000 bending cycles. This work presents a less complex and solution-processed efficient catalyst for future electrochemical energy applications.

Honeycomb-like biomass carbon with planted CoNi3 alloys to form hierarchical composites for high-performance supercapacitors

It is a significant challenge to combine a large pseudocapacitive material with conductive honeycomb-like carbon frameworks for long-term stable supercapacitors. Herein, hierarchical composite materials are manufactured by using biomass carbon, ZIF-67, and a mild pore former (Ni(CH₃COO)₂) to generate alloy-type CoNi₃ nanoparticles planted into conductive honeycomb-like carbon frameworks (C@ZIF-67-T). Meanwhile, the effect of carbonization temperature on the honeycomb-like pore size and the structure of composite materials is systematically investigated. As the honeycomb-like carbon skeleton structure guarantees good ionic and electronic conductivities and a large contact area, whereas the alloy nanoparticles provide a rich redox reaction for Faradaic capacitance. Therefore, the as-obtained C@ZIF-67-600 electrode presents a remarkable specific capacitance of 1044.8 F · g^-1 at 1.0 A · g^-1 and an ultra-long cycling stability with 30,000 cycles at 5.0 A · g^-1 in a three-electrode system. In addition, the assembled C@ZIF-67-600//activated carbon asymmetrical supercapacitor exhibit a high specific capacitance of 274.4F · g^-1 at 1.0 A · g^-1 and a long-term stable lifespan with a capacitance retention of 87% after 20,000 cycles at 5.0 A · g^-1. Besides, the asymmetrical supercapacitor also presents a maximum energy density of 85.13 Wh · kg^-1 at a power density of 750 W · kg^-1. Such superior electrochemical performance demonstrate that the designed electrode material provides a promising energy storage application.

Noble-metal-free Fe3O4/Co3S4 nanosheets with oxygen vacancies as an efficient electrocatalyst for highly sensitive electrochemical detection of As(III)

The electrochemical method for highly sensitive determination of arsenic(III) in real water samples with noble-metal-free nanomaterials is still a difficult but significant task. Here, an electrochemical sensor driven by noble-metal-free layered porous Fe₃O₄/Co₃S₄ nanosheets was successfully employed for As(III) analysis, which was prepared via a facile two-step method involves a hydrothermal treatment and a subsequent sulfurization process. As expected, the electrochemical detection of As(III) in 0.1 M HAc-NaAc (pH 6.0) by square wave anodic stripping voltammetry (SWASV) with a considerable sensitivity of 4.359 μA/μg·L^-1 was obtained, which is better than the commonly used noble metals modified electrodes. Experimental and characterization results elucidate the enhancement of As(III) electrochemical performance could be attributed to its nano-porous structure, the presence of oxygen vacancies and strong synergetic coupling effects between Fe₃O₄ and Co₃S₄ species. Besides, the Fe₃O₄/Co₃S₄ modified screen printed carbon electrode (Fe₃O₄/Co₃S₄-SPCE) shows remarkable stability and repeatability, valuable anti-interference ability and could be used for detection in real water samples. Consequently, the results confirm that as-prepared porous Fe₃O₄/Co₃S₄ nanosheets is identified as a promising modifier to detect As(III) in real sample analysis.

Synergistically modified WS2@PANI binary nanocomposite-based all-solid-state symmetric supercapacitor with high energy density

WS2@PANI nanocomposite prepared by hydrothermal and physical blending method shows remarkably high specific capacitance and energy density while retaining excellent cyclic stability.

Heterostructured Co-NTC@Co3S4 as an anode material for asymmetric pseudocapacitors

Herein, a composite structure of ZIF-67@Co-NTC was synthesized and it was partially vulcanized to form layer-like Co3S4 nanosheets to finally successfully synthesize a composite heterostructure of Co-NTC@Co3S4.

A novel zinc sulfide impregnated carbon composite derived from zeolitic imidazolate framework-8 for sodium-ion hybrid solid-state flexible capacitors

The pyrolysis of metal-organic frameworks (MOFs) is an easy approach to prepare metal oxides as well as nanoporous carbon with high specific surface area. In the present work, for the first time, ZIF-8 (zeolitic imidazolate framework-8) has been pyrolyzed under different conditions to derive two products, i.e., highly porous carbon (C) and zinc sulfide (ZnS) infused carbon (ZnS@C). These two materials, i.e., nanoporous C and ZnS@C, have been investigated as a negative and a positive electrode, respectively, for potential application in a hybrid asymmetrical solid-state supercapacitor device (HASD). The controlled pyrolysis approach for the preparation of ZnS@C has yielded uniformly distributed ZnS nanoparticles inside the carbon structure. A 1.8 V HASD has been assembled, which delivered an excellent energy density of 38.3 W h kg^-1 (power density of 0.92 kW kg^-1) along with the greatly desirable feature of cycling stability. The proposed selection of materials as electrodes is promising to develop futuristic hybrid capacitors.

Transition metal dichalcogenide (TMDs) electrodes for supercapacitors: a comprehensive review

As globally, the main focus of the researchers is to develop novel electrode materials that exhibit high energy and power density for efficient performance energy storage devices. This review covers the up-to-date progress achieved in transition metal dichalcogenides (TMDs) (e.g. MoS₂, WS₂, MoSe_2,and WSe₂) as electrode material for supercapacitors (SCs). The TMDs have remarkable properties like large surface area, high electrical conductivity with variable oxidation states. These properties enable the TMDs as the most promising candidates to store electrical energy via hybrid charge storage mechanisms. Consequently, this review article provides a detailed study of TMDs structure, properties, and evolution. The characteristics technique and electrochemical performances of all the efficient TMDs are highlighted meticulously. In brief, the present review article shines a light on the structural and electrochemical properties of TMD electrodes. Furthermore, the latest fabricated TMDs based symmetric/asymmetric SCs have also been reported.

Amorphous Co3S4 nanoparticle-modified tubular g-C3N4 forms step-scheme heterojunctions for photocatalytic hydrogen production

An effective method to reduce the recombination rate of photogenerated electron–hole pairs was developed by the construction of heterojunctions with rationally designed photocatalysts having a matched band structure.

Fabrication of 2D/2D nanosheet heterostructures of ZIF-derived Co3S4 and g-C3N4 for asymmetric supercapacitors with superior cycling stability

Asymmetric supercapacitors with superior cycling stability are achieved by designing 2D/2D nanosheet heterostructures of ZIF-derived Co₃S₄ and g-C₃N₄.