Extraordinary Electrochemical Properties Research Articles

Hierarchical porous 3D Ni3N-CoN/NC heterojunction nanosheets with nitrogen vacancies for high-performance flexible supercapacitor

In the realm of everyday existence, the allure of flexible portable electronic devices has captured widespread attention. Consequently, the imperative to conceive and fabricate flexible energy storage/conversion systems assumes paramount significance. Transition metal nitrides (TMNs), distinguished by their extraordinary electrochemical properties, emerge as compelling candidates for electrode materials in high-performance energy storage devices. This study undertakes the synthesis of three-dimensional Ni3N-CoN/NC heterojunction nanosheets via a meticulous two-step in situ growth process involving metal organic frameworks (MOFs) on carbon cloth (CC), succeeded by annealing in an ammonia-rich environment. The ensuing nitridation engenders copious ion pathways, engrossing a considerable specific surface area of 233.2 m2 g−1 and endowing nitrogen vacancies in abundance. The augmented conductivity of the nitrogen-vacancy-rich heterojunction is corroborated through density functional theory calculations. Employed as a flexible freestanding supercapacitor electrode, the Ni3N-CoN/NC/CC configuration evinces a marked enhancement in electrochemical performance attributable to its superior intrinsic conductivity and heightened active sites. Notably, the synthesized Ni3N-CoN/NC/CC flexible electrode showcases a remarkable specific capacitance of 468.3 mA h g−1 at a current density of 3 A g−1. Moreover, the integration of the Ni3N-CoN/NC/CC cathode with an activated carbon (AC) anode in a flexible asymmetric supercapacitor (ASC) yields an impressive energy density of 0.2144 mWh cm−2 and a maximum power density of 80 mW cm−2, exhibiting exceptional cycling stability of 92.3% even after 15,000 cycles. The exceptional performance exhibited by the synthesized freestanding Ni3N-CoN/NC/CC composite underscores its tremendous potential in the development of flexible energy storage devices.

Weaving Aerogels into 3D Ordered Hyperelastic Hybrid Carbon Assemblies.

The development of a 3D carbon assembly with a combination of extraordinary electrochemical and mechanical properties is desirable yet challenging. Herein, an ultralight and hyperelastic nanofiber-woven hybrid carbon assembly (NWHCA) is fabricated by nanofiber weaving of isotropic porous and mechanical brittle quasi-aerogels. Upon subsequent pyrolysis, metallogel-derived quasi-aerogel hybridization and nitrogen/phosphorus co-doping are integrated into the NWHCA. Finite element simulation indicates that the 3D lamella-bridge architecture of NWHCA with the quasi-aerogel hybridization contributes to resisting plastic deformation and structural damage under high compression, experimentally demonstrated by complete deformation recovery at 80% compression and unprecedented fatigue resistance (>94% retention after 5000cycles). Due to the superelasticity and quasi-aerogel integration, the zinc-air battery assembled based on NWHCA shows excellent electrochemical performance and flexibility. A proof-of-concept integrated device is presented, in which the flexible battery powers a piezoresistive sensor, using the NWHCA as the air cathode and the elastic conductor respectively, which can detect full-range and sophisticated motions while attached to human skin. The nanofiber weaving strategy allows the construction of lightweight, superelastic, and multifunctional hybrid carbon assemblies with great potential in wearable and integrated electronics.

Carbon superstructure nanoflower derived from self-assembly of polyimide for superior lithium storage

In this paper, three-dimensional carbon superstructures (CSSs) have been proposed through an effective method. Specifically, the hierarchical self-assembly of polyimide (PI) is followed by thermal annealing. Moreover, the structural evolution of PI under the various pyrolysis time was also comprehensively studied. It is noted that the as-prepared CSSs as anode composites for LIBs, especially CSS-5 h, exhibited extraordinary electrochemical properties, exhibiting a high reversible performance, great rate performance, and excellent cycling stability. As expected, the superior electrochemical capability can be ascribed to the synergistic effect of combining the nanoflower-like carbon superstructures with nitrogen contents. Such a method might encourage the inspirations to devise and obtain various heteroatom-modulated and hierarchical polymer-derived carbon composites for LIBs.

Molecular and atomic manipulation of metal-organic framework-derived LiCoMnO4: An oxygen-deficient strategy for advanced lithium storage

As a novel class of high-voltage cathode materials, spinel lithium transition metal oxides have been faced with demerits including pronounced structural instability caused by Jahn-Teller distortion (especially at the lower voltage region) and severe capacity degradation despite their intriguing electrochemical properties. To extend their functionalities as broad-voltage cathodes, the sacrificial template method has been regarded as a promising way to realize structural and compositional control for desirable electrochemical behaviors. Herein, we report a synthetic protocol to directionally prepare LiCoMnO4 (LCMO) using carboxyl-based metal-organic frameworks (MOFs) as self-sacrificing templates. Impressively, LCMO derived from CoMn-BDC (H2BDC = 1,4-benzenedicarboxylate) displays superior electrochemical performances with a specific capacity of 151.6 mAh g−1 at 1 C (150 mA g−1) after 120 cycles and excellent rate capacity of 91.9 mAh g−1 at 10 C due to the morphology control, microstructural modulation, and atomic manipulation of the MOF precursor. Bestowed by the optimized atomic and electronic structure, abundant oxygen vacancies, and the nanostructure retained from MOF precursors, LCMO materials display extraordinary electrochemical properties, which have been extensively verified by both experimental and theoretical studies. This work not only provides guidelines for the directional design of spinel materials at molecular and atomic levels but also sheds light on the practical use of LIBs with broad range voltage.

Formation mechanism of nano graphitic structures during microwave catalytic graphitization of activated carbon

Catalytic graphitization of biomass-based carbon has been used to synthesize graphene nanostructures with extraordinary electrochemical properties. To further improve the structural properties of these graphene nanostructures, it is critical to gain a deeper understanding of the formation mechanism and influence of process variables on the structural features of the resulting material. Here, we report the impact of various parameters such as catalyst loading, temperature, holding time, and catalyst salt precursor on the low-temperature catalytic graphitization of activated carbon (AC). Quantitative X-ray diffraction (XRD) analysis results show that at 20 wt% catalyst loading, reaction temperature of 1400 °C, and holding time of 30 min, a complete graphitization of amorphous carbon was achieved. In situ XRD and transmission electron microscopy (TEM) results indicated that the dissolution-precipitation and metal-induced graphitization are the primary mechanisms under which graphitized carbon was formed. Furthermore, it was found that the rate of graphitization under microwave irradiation is significantly higher than conventional heating, mainly owing to the enhanced precipitation of graphitic carbon caused by both carbon saturation and temperature fluctuation of the catalyst particles.

Nest-Like MnO2 Nanowire/Hierarchical Porous Carbon Composite for High-Performance Supercapacitor from Oily Sludge.

In the aim to go beyond the performance tradeoffs of classic electric double-layer capacitance and pseudo-capacitance, composites made out of carbon and pseudo-capacitive materials have been a hot-spot strategy. In this paper, a nest-like MnO2 nanowire/hierarchical porous carbon (HPC) composite (MPC) was successfully fabricated by a controllable in situ chemical co-precipitation method from oily sludge waste. Due to the advantages of high surface area and fast charge transfer for HPC as well as the large pseudo-capacitance for MnO2 nanowires, the as-prepared MPC has good capacitance performance with a specific capacitance of 437.9 F g−1 at 0.5 A g−1, favorable rate capability of 79.2% retention at 20 A g−1, and long-term cycle stability of 78.5% retention after 5000 cycles at 5 A g−1. Meanwhile, an asymmetric supercapacitor (ASC) was assembled using MPC as the cathode while HPC was the anode, which exhibits a superior energy density of 58.67 W h kg−1 at the corresponding power density of 498.8 W kg−1. These extraordinary electrochemical properties highlight the prospect of our waste-derived composites electrode material to replace conventional electrode materials for a high-performance supercapacitor.

Leaf-like integrated hierarchical NiCo2O4 nanorods@Ni-Co-LDH nanosheets electrodes for high-rate asymmetric supercapacitors

In order to diminish charge transfer resistance and improve rapid reversible redox reactions of supercapacitors, leaf-like hierarchical NiCo2O4 nanorods@Ni-Co-layered double hydroxide nanosheets (NCO@Ni-Co-LDH) core/shell nanostructure was synthesized by two-step oxalic acid-assisted and metal organic framework (MOF)-derived method. Firstly, NCO nanorods as a core structure were synthesized in the presence of oxalic acid as an oxidizing agent. Then, Ni-Co-LDH as a shell structure was prepared by MOF-based synthesis. As-prepared hybrid core/shell NCO@Ni-Co-LDH electrodes displayed the highest capacitance (2370 F g−1 under 1 A g−1), exceptional rate-capability (78.2% at 30 A g−1) and a remarkable lifespan of 86.4% after successive 5000 charge/discharge performance. These extraordinary electrochemical properties are ascribed to the synergistic effects of NCO nanorods and Ni-Co-LDH nanosheets in a single core/shell structured framework, providing more accessible electroactive sites for rapid redox reactions with superior mechanical stability for longer cycle during charge-discharge cycles. Furthermore, an asymmetric NCO@Ni-Co-LDH//N-doped graphene hydrogel (NGH) supercapacitor delivered excellent energy density (50.71 Wh kg−1), high power density (773.54 W kg−1), and remarkable cyclic lifespan (89% after 5000 cycles under 5 A g−1).

Interfacial adsorption–insertion mechanism induced by phase boundary toward better aqueous Zn‐ion battery

AbstractBiphasic and multiphasic compounds have been well clarified to achieve extraordinary electrochemical properties as advanced energy storage materials. Yet the role of phase boundaries in improving the performance is remained to be illustrated. Herein, we reported the biphasic vanadate, that is, Na1.2V3O8/K2V6O16·1.5H2O (designated as Na0.5K0.5VO), and detected the novel interfacial adsorption–insertion mechanism induced by phase boundaries. First‐principles calculations indicated that large amount of Zn2+ and H+ ions would be absorbed by the phase boundaries and most of them would insert into the host structure, which not only promote the specific capacity, but also effectively reduce diffusion energy barrier toward faster reaction kinetics. Driven by this advanced interfacial adsorption–insertion mechanism, the aqueous Zn/Na0.5K0.5VO is able to perform excellent rate capability as well as long‐term cycling performance. A stable capacity of 267 mA h g−1 after 800 cycles at 5 A g−1 can be achieved. The discovery of this mechanism is beneficial to understand the performance enhancement mechanism of biphasic and multiphasic compounds as well as pave pathway for the strategic design of high‐performance energy storage materials.image

The influence of reduced graphene oxide on stem cells: a perspective in peripheral nerve regeneration.

Graphene and its derivatives are fascinating materials for their extraordinary electrochemical and mechanical properties. In recent decades, many researchers explored their applications in tissue engineering and regenerative medicine. Reduced graphene oxide (rGO) possesses remarkable structural and functional resemblance to graphene, although some residual oxygen-containing groups and defects exist in the structure. Such structure holds great potential since the remnant-oxygenated groups can further be functionalized or modified. Moreover, oxygen-containing groups can improve the dispersion of rGO in organic or aqueous media. Therefore, it is preferable to utilize rGO in the production of composite materials. The rGO composite scaffolds provide favorable extracellular microenvironment and affect the cellular behavior of cultured cells in the peripheral nerve regeneration. On the one hand, rGO impacts on Schwann cells and neurons which are major components of peripheral nerves. On the other hand, rGO-incorporated composite scaffolds promote the neurogenic differentiation of several stem cells, including embryonic stem cells, mesenchymal stem cells, adipose-derived stem cells and neural stem cells. This review will briefly introduce the production and major properties of rGO, and its potential in modulating the cellular behaviors of specific stem cells. Finally, we present its emerging roles in the production of composite scaffolds for nerve tissue engineering.

Three‐dimensional printing of high‐mass loading electrodes for energy storage applications

AbstractNanostructured materials afford a promising potential for many energy storage applications because of their extraordinary electrochemical properties. However, the remarkable electrochemical energy storage performance could only be harvested at a relatively low mass‐loading via the traditional electrode fabrication process, and the scale of these materials into commercial‐level mass‐loading remains a daunting challenge because the ion diffusion kinetics deteriorates rapidly along with the increased thickness of the electrodes. Very recently, three‐dimensional (3D) printing, a promising additive manufacturing technology, has been considered as an emerging method to address the aforementioned issues where the 3D printed electrodes could possess elaborately regulated architectures and rationally organized porosity. As a result, the outstanding electrochemical performance has been widely observed in energy storage devices made of 3D printed electrodes of high‐mass loading. In this review, we systemically introduce the basic working principles of various 3D printing technologies and their practical applications to manufacture high‐mass loading electrodes for energy storage devices. Challenges and perspectives in 3D printing technologies for the construction of electrodes at the current stage are also outlined, aiming to offer some useful opinions for further development for this prosperous field.image

Predictive data regression technique based carbon nanotube biosensor for efficient patient health monitoring system

In many ways, monitoring the patient's health with appropriate sensors to monitor the hospital’s connection, as if the patient is lying in bed. The previous method of monitoring can be uncomfortable for a variety of reasons. Tracking a growing number of patients requires many trained health professionals and doctors. The proposed predictive data regression technique (PDRT) based carbon nanotubes (CNT) biosensor system has been introduced in the fields like Biomedical. In this analysis technique, the sensor value is compared to the threshold value; if any changes occur, the controller sends the user alert via IoT. The patients are present in this area so that their physicians and many physiological measurements and applications can be seen. Carbon nanotubes (CNT) have been used as electronic mediators and adsorption substrates in biosensors due to their extraordinary electrochemical properties. Explore its potential biosensing applications, platinum, carbon nanomaterials, electrochemical electrode preparation and features. The purpose of this proposal is to maintain a system of inpatient physiological parameters and activity. The physician can see a graphical view of the patient's parameters and a computer system worn by the patient, the Wi-Fi network, and the display. Abnormalities inpatient data are messages sent to the doctor via an IoT system to remind them of the situation. The Proposed Predictive Data Regression Technology (PDRT) system is given a better performance to the user, and it provides the output accuracy.

Forest-like carbon foam templated rGO/CNTs/MnO2 electrode for high-performance supercapacitor

Inspired by the unique structure of the forest in nature, a hierarchical carbon foam templated rGO/CNTs/MnO2 composite has been successfully fabricated by electrophoresis deposition, chemical vapor deposition and electrochemical deposition, in aims of combining the high mechanical stability of porous 3D carbon foam framework, the large specific surface area of 2D graphene and the fast charge transfer property of 1D CNTs, as well as the large pseudo-capacitance of MnO2 nanoparticles. The electrochemical performances were carefully investigated in a three-electrode system and compared with CF-rGO and CF-rGO/CNTs prepared by the same method. The results reveal that, CF-rGO/CNTs/MnO2 exhibits the highest specific capacitance (332.5 F/g at 0.5 A/g) among the three electrodes, with an excellent capacitance retention as high as 89.2% after running for 10,000 cycles at 5 A/g. Meanwhile, an asymmetric supercapacitor was assembled using CF-rGO/CNTs/MnO2 as positive electrode while active carbon as negative electrode, which exhibits an extended operating potential window ranging from 0 to 1.8 V and a superior energy density of 41.6 Wh/kg at corresponding power density of 513.7 W/kg. These extraordinary electrochemical properties give the as-prepared composite great potential to replace conventional electrode materials as high energy storage supercapacitors.

Tailoring the surface in copper manganese oxide materials and enhanced redox nature by graphitic carbon nitride sheets with ultra-long life for electrochemical applications

Designing different micro/nanostructured materials with high electrical conductivity and porosity has attracted great attention, making their extraordinary electrochemical properties available in energy storage fields.

Flexible supercapacitor of high areal performance with vanadium/cobalt oxides on carbon nanofibers as a binder-free membrane electrode

For flexible capacitive energy storage units in wearable devices, areal metrics, such as areal capacitance and energy density, are exceptionally important, because of limitations on device volume and weight. One-dimensional carbon nanofibers composited with active metal oxides, such as cobalt monoxide (CoO), possess extraordinary electrochemical properties. However, low areal metrics and the polarity in the flexible asymmetric supercapacitor device are two crucial challenges. Herein, vanadium/cobalt oxides on carbon nanofibers (VCO/CNFs) are purposely designed and fabricated by electrospinning and controllable post-calcination, which can be used as a binder-free non-polarity membrane electrode for the assembly of high-performance flexible supercapacitor (FSC). Importantly, the rational incorporation of vanadium with varying valence states helps promote the formation of CoO phase, enriches the reaction sites and enhances the capability of local electron transport. As expected, the single electrode of VCO/CNFs yields an extraordinarily high areal capacitance of 1.83 F cm−2 at the current density of 8 mA cm−2. The as-obtained FSC with VCO/CNFs as both anode and cathode delivers an excellent areal energy density of 44.2 μWh cm−2 at a power density of 2.8 mW cm−2, a long-term cycling stability (retention rate of 95.2% over 10,000 cycles), and a good flexibility under even various bending conditions. To our best knowledge, these areal metrics are among the superior values reported.

CoFe2O4 Nanoparticle-Decorated 2D MXene: A Novel Hybrid Material for Supercapacitor Applications

The development of highly efficient electrode materials for high power devices is one of the cutting-edge research areas in advanced energy applications. Recently, MXene has gained tremendous interest among the research community because of its extraordinary electrochemical properties as compared to other two-dimensional layered materials such as graphene/MoS₂. However, the supercapacitive performance of MXene as an electrode material is hindered by the restacking of its layers due to functional group interactions. To overcome this problem, here in this article, we explored MXene and its composites with cobalt ferrite [CoFe₂O₄] nanoparticles (CoF NPs) for battery-like hybrid supercapacitor applications. NPs were applied to use them as interlayer spacers between MXene layers. By the electrochemical studies, it is proved that the composite (CoF/MXene) can provide better electrochemical properties than individual ferrite or MXene. The maximum specific capacitance (Cₛₚ) of CoF NPs, MXene, and CoF/MXene composites was observed to be about 594, 1046.25, and 1268.75 Fg–¹ at 1 A g–¹, respectively. The calculated specific capacity (sp. capacity) of the CoF/MXene composite was about 440 Cg–¹ at 1 A g–¹ and proved to be an excellent hybrid electrode material by providing only 0.25 Ω charge transfer resistance. The as-synthesized material demonstrated the excellent capacitance retention, about 97%, up to 5000 cycles.

Facile Synthesis of Hierarchical MgCo2O4@MnO2 Core-Shell Nanosheet Arrays on Nickel Foam as an Advanced Electrode for Asymmetric Supercapacitors

Ternary transition metal oxides (TTMOs) material has recently drawn significant interests to researchers, as a potential electrode material to advance the energy storage technology. In this paper, the hierarchical MgCo2O4@MnO2 core-shell nanosheet arrays (CNAs) were resoundingly fabricated on nickel foam using a simple solvothermal reaction and a calcination afterwards. The assembled MgCo2O4@MnO2 electrode had a specific capacity of 968.98 C g−1 under 1 mA cm−2 in a 1 M KOH solution. Additionally, two asymmetric supercapacitors (ASCs) were assembled, one with PVA-KOH gel (PKG) as electrolyte and the other with KOH solution as electrolyte. Both of the ASCs were made with MgCo2O4@MnO2 CNAs/Ni foam as the positive electrode and the activated carbon (AC) as the negative electrode, and both exhibited extraordinary electrochemical properties. The remarkable electrochemical performance revealed that the MgCo2O4@MnO2 nanomaterial was a prospective electrode material and can be applied potentially in energy storage field.

Advanced Ultrathin RuPdM (M = Ni, Co, Fe) Nanosheets Electrocatalyst Boosts Hydrogen Evolution.

The hydrogen evolution reaction (HER) is one of the most significant reactions in the electrolysis water process, and electrocatalysts which possess high mass activity and excellent stability are the most important driving factors to improve the efficiency of HER. As for the efficient commercially electrocatalyst, Pt/C is limited in development because of its high cost. Therefore, the study of non-Pt high-efficiency catalysts is particularly important at this moment. Here, we creatively report for the first time a kind of RuPdM (M= Ni, Co, Fe) ultrathin nanosheets (NSs), which exhibit extraordinary electrochemical properties for HER under alkaline conditions. The overpotential of optimized trimetallic Ru38Pd34Ni28 ultrathin NSs is only 20 mV (10 mA cm–2), and the mass activity reaches 6.15 A mg–1noble metal at −0.07 V vs RHE. It can be compared to Pt-based electrocatalysts, which have the highest mass activity currently reported. The durability tests also prove that the stability of the electrocatalyst is outstanding. DFT calculations disclose that the flexible modulation of electronic structures of RuPd ultrathin NSs is achieved by utilizing the additional 3d transition metals Fe, Co, and Ni. In particular, the Ni-3d bands act as the continuous electron-supply center for Ru to ensure an efficient electron transfer toward the adsorbates. Meanwhile, the stable Pd sites are critical for coupling the O-2pπ orbital in the initial H2O splitting with a facile barrier. This work will open up a new era of non-Pt materials for alkaline hydrogen evolution toward practical application.

Graphene Quantum Dots in Electrochemical Sensors/Biosensors

Background:Graphene and its derivatives, as most promising carbonic nanomaterials have been widely used in design and making electrochemical sensors and biosensors. Graphene quantum dots are one of the members of this family which have been mostly known as fluorescent nanomaterials and found extensive applications due to their remarkable optical properties. Quantum confinement and edge effects in their structures also cause extraordinary electrochemical properties.Objective:Recently, graphene quantum dots besides graphene oxides and reduced graphene oxides have been applied for modification of the electrodes too and exposed notable effects in electrochemical responses. Here, we are going to consider these significant effects through reviewing some of the recent published works.

Cryptomelane-type MnO2/carbon nanotube hybrids as bifunctional electrode material for high capacity potassium-ion full batteries

Potassium-ion batteries (PIBs) have been receiving a great deal of attention owing to abundant and cost-effective potassium resources. However, the key issue is to explore suitable electrode materials for accommodating the large size K-ions reversibly. In this report, K1.06Mn8O16/CNT hybrids are systematically studied for the first time as bifunctional PIBs-electrodes, in which Mn-ions play as the redox center. As the cathode, it exhibits excellent electrochemical kinetics and reversibility, as well as highly structure stability. The cathode displays an unprecedented capacity of 309.4 mA h g−1 at 20 mA g−1 with the energy density of 733.3 Wh kg−1 and outstanding rate performance (187.1 mA h g−1 at 500 mA g−1). In addition, the high capacity of 636.6 mA h g−1 at 20 mA g−1, ultra-long cycling lifespan over 500 cycles and remarkable rate capability can also be acquired when the material was tested as the anode. The extraordinary electrochemical properties are ascribed to the well-developed conductive network and robust microstructure stability. Meanwhile, the symmetrical K-ions full cell exhibits high discharge capacity of 241.0 mA h g−1 at 100 mA g−1. This work reveals the K-ions storage mechanism in cryptomelane bifunctional electrodes in depth and the fundamental understanding help us open up a new direction for PIBs.

Strong interface coupling and few-crystalline MnO2/Reduced graphene oxide composites for supercapacitors with high cycle stability

Long cycle life has been the key factor that inhibits the practical application of transition metal oxides (TMOs)-based pseduocapacitors, due to their poor electrical conductivity and the limited interface charge transfer between TMOs and conductive substrates. We here demonstrate a novel strategy to address this issue by constructing strongly coupled, few-crystalline MnO2 nanosheets/reduced graphene oxide (rGO) composites. The covalent linkage of COMn at the interface effectively improves the charge transfer efficiency, avoiding the detachment of MnO2 nanosheets from rGO surfaces during the charge/discharge. Meanwhile, the few-crystalline MnO2 nanosheets are able to retain good structural integrity for the long cycling duration at large current densities. In the process of galvanostatic charge/discharge, the resulting composite electrode reveals a specific capacitance up to 234.8 F g−1 at 0.1 A g−1 and a 100% of capacitance retention after 20,000 cycles at 10 A g−1 in neutral Na2SO4 electrolyte. These extraordinary electrochemical properties reflect the synergistic role that the interface design and crystal structure control play in optimizing the performance of TMO-based pseduocapacitors.