Electroactive Sites Research Articles

Unveiling the Collaborative Strategy and Synergistic Effects of Pd/V2O5‐fAC towards Glycerol Electrooxidation

AbstractA series of Pd nanoparticles supported on V2O5 immobilized on functionalized carbon, % Pd (1, 3, and 5) and % V2O5 (10, 20, and 30), were prepared by sodium borohydride‐assisted microwave polyol synthesis for glycerol oxidation reaction (GlyOR) in an alkaline medium. Electrocatalysts loading, temperature, V2O5 immobilization, and their synergistic effect on the electrocatalytic performance are systematically studied. The electrocatalysts′ morphology and electronic properties were investigated using X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, Transmission electron microscopy, and X‐ray photoelectron spectroscopy. A significantly improved GlyOR is observed with increased V2O5 content and Pd percentage. The 5 %Pd/30 %V2O5‐fAC showed the highest mass activity of 2157.3 mA . mgPd−1, a more negative onset potential of 0.62 VRHE, versus the commercial equivalent, and possessed high stability and durability. The increase in electrocatalytic activity is attributed to the effective immobilization of V2O5 on fAC efficient synergism between Pd and V2O5, strong metal support interaction (SMSI), and great exposure of the electroactive sites. The results herein contribute significantly to the understanding of the physicochemical and electrochemical effects of metal oxide immobilization, microwave irradiation, % Pd/% Metal oxide optimization, and SMSI on metal oxide‐carbon hybrid electrocatalysts for GlyOR, opening new avenues for fabricating high‐performance direct alkaline glycerol fuel cells.

Heterostructured flower‐like NiO/Co3O4 microspheres modified by bifunctional carbon quantum dots as a battery‐type cathode for high energy and power density hybrid supercapacitors

AbstractHybrid supercapacitors (HSCs) comprising a battery‐type cathode and capacitive anode have recently become a research hotspot. Nevertheless, the low capacity utilization, poor kinetic behavior, and unstable structure of a single battery‐type oxide cathode restrict the overall performance of the device. Herein, the carbon quantum dots (CQDs) modified NiO/Co3O4 heterostructured flower‐like microspheres are constructed, and enhanced specific capacity, rate capability, and cycling performance are achieved when used as the cathode for HSCs. This is attributed to the fact that the modification of bifunctional CQDs as size regulators and conductive agents and the construction of heterostructure can not only improve the specific surface area and provide more electroactive sites, thereby enhancing the charge storage performance but also regulate the electronic structure and boost the interface charge transfer capability and electronic conductivity, thereby boosting the reaction kinetics and cycle stability. The enhanced electrochemical kinetic behavior is revealed by electrochemical kinetic analyses based on cyclic voltammetry, electrochemical impedance spectroscopy tests and density functional theory calculations. Meanwhile, the electrochemical reaction process and energy storage mechanism are illustrated by ex‐situ X‐ray diffraction and X‐ray photoelectron spectroscopy characterizations. Furthermore, an HSC is further constructed using the CQDs/NiO/Co3O4 heterostructured flower‐like microspheres as the cathode, simultaneously achieving high energy density (40.9 Wh kg−1), high power density (24 kW kg−1), and splendid cyclic stability (94.2% capacity retention after 5000 cycles at 10 A g−1). These synergistic modification strategies of bifunctional CQDs modification and heterostructure design provide a valuable direction for the design and development of HSCs with both high energy density and high power density.

Heterostructured Ni2P/NiMo-layered double hydroxide nanoarrays with enriched redox active sites for supercapacitors

The electroactivity and cyclic stability of transition metal phosphides (TMPs) for supercapacitors are restricted by inadequate redox active sites and huge volume changes during the charging/discharging process. Herein, a three-dimensional (3D) porous Ni2P/NiMo-layered double hydroxide (NiMo-LDH) heterostructure with large specific surface and abundant pore channels is explored as a self-supporting supercapacitor electrode. The well-defined hierarchical pore structure can offer numerous electroactive sites and short ion/electron pathways. The generation of heterointerfaces between multi-dimensional Ni2P and two-dimensional (2D) NiMo-LDH nanosheets endows the hybrid composite with improved electrical conductivity and structural robustness. Consequently, the special nanoarchitecture design achieves a specific capacity of 198.6 mAh g−1 (2.28 mAh cm−2) at 1 A g−1 and an impressive rate performance of 78.3% at 20 A g−1. More importantly, the assembled Ni2P/NiMo-LDH//orange peel-derived porous carbon (OPC) asymmetric supercapacitor (ASC) device delivers a remarkable specific energy of 63.7 Wh kg−1 at a specific power of 1138.3 W kg−1 and long-term cycling stability (91.7% over 10,000 cycles). The research highlights that the hybridization of TMPs and other nanostructured battery-type materials may produce a synergistic effect and boost the capacitive properties.

Nanoparticles of poly(3-hexylthiophene): Toward a solvent-independent performance of electrochromic films

Nanoparticles of poly(3-hexylthiophene), P3HT(NP), uniquely enable the preparation of stable dispersions in environmentally-friendly media and thus offer a sustainable liquid phase fabrication of electrochromic device structures. In this work, we assess the electrochromic performance of P3HT(NP) films spray-coated from either tetrahydrofuran (THF)-water or chloroform (CHCl3)-ethanol dispersions on ITO substrates. The nanoparticle films exhibit consistent and reproducible high optical contrast values of around 50 %, t90-switching speeds of about 0.45 s and a cycling stability of approximately 200 cycles for a 20 % performance retention, independent of the solvent being used. Conversely, non-nanostructured P3HT films spray-coated from THF or CHCl3 reveal a strong solvent dependent variability in their electrochromic behavior presenting low optical contrast, high switching speeds and fast degradation rates in the case of CHCl3. The solvent independent electrochromic characteristics of P3HT nanoparticle films is related to a consistent availability of accessible electroactive sites provided by a homogeneous porous P3HT network structure formed on the underlying substrate, as probed by SEM and profilometric studies. Our findings reveal that the use of nanoparticles of P3HT and its environmentally benign liquid phase processing, a concept which is extendable to other electrochromic polymers, opens a sustainable pathway toward the large-area fabrication of electrochromic device structures with favorable and consistent performance parameters.

Robust water splitting based on new microporous hybrid iron cobalt phosphonate as efficient bifunctional electrocatalyst

The facile synthesis of microporous hybrid bimetallic iron-cobalt phosphonate (FeCoNAPH) has been reported under easy hydrothermal condition without using any kind of template. With the lower overpotential values of 154 and 132 mV at 10 mA cm−2 and having lower Tafel slopes, the electrocatalyst displays outstanding catalytic activities for OER and HER, repetitively in basic medium. The as-synthesized FeCoNAPH is a cost-effective material employed in practical applications, and it is analogous to the standard catalysts such as IrO2 and Pt/C (10 wt%). Having a high specific surface area with regular microporosity, the FeCoNAPH displays exceptional electrocatalytic activity, which could be utilized for commercialization purposes in the future to substitute the high-cost effectiveness and scarcity of noble metals. Additionally, the as-synthesized electrocatalyst exhibits long-term durability with the required cell potential of 1.43 V to attain 10 mA cm−2 for a two-electrode overall water splitting (OWS) system. Notably, the spherical structure helps in the production of a greater number of electroactive sites, which leads to a faster rate of kinetics of the development of electroactive intermediate species.

Wire-type flexible micro-supercapacitor based on MOF-assisted sulfide nano-arrays on dendritic CuCoP and V2O5-polypyrrole/nanocellulose hydrogel

Wire/fiber-type micro-supercapacitors (micro-SCs) have great potentials in next-generation wearable and portable energy supply devices, due to their low weight, high flexibility, small size and excellent reliability. Herein, we designed 2D-3D S-doped CoZnNi-OH/CuCoP positive microelectrode with hierarchical structure on 1D metal fiber substrate for high-capacitance fibrous micro-SCs. Such unique architecture, which 2D S-doped CoZnNi-OH nanosheet arrays vertically aligned on 1D Cu wire garnished with 3D dendritic CuCoP through CoZn-MOF template, exposed ample electroactive sites, created robust electrical and mechanical joint between nanostructured material and metal fiber, and promote the transport/diffusion rate of ions. The achieved 2D-3D S-doped CoZnNi-OH/CuCoP/CW microelectrode exhibited the areal/volumetric/length capacitances of 2.9 F cm−2, 290.07 F cm−3, and 348 mF cm−1 at 4 mA cm−2, respectively, which is 18 times of the sulfide directly co-electrodeposited on 3D CuCoP foam without MOF template. Besides, negative microelectrode was prepared through electrochemical deposition of V2O5-PPy on 1D carbon fiber substrate decorated with rGO-nanocellulose (NC) hydrogel. The electrical double layer capacitance behavior combined with pseudocapacitive properties enhances charge storage performance of fibrous microelectrode in terms of specific capacitance, cycle stability and rate capability. The fabricated solid-state 2D-3D S-doped CoZnNi-OH/CuCoP/CW//V2O5-PPy/rGO-NC/CF micro-SC presents high areal energy density of 127.62 µWh cm−2 at a power density of 1.83 mW cm−2 and durability (93.7 % retention after 5000 cycles) with excellent mechanical flexibility. Giving the versatility of 1D carbon/metal fiber substrates, template-assisted 3D architecture, MOF-derived sulfide nanoarrays, and NC chemical reactivity, the proposed strategy can be used for construction of other next-generation miniaturized portable electronics.

Can perfluorooctanoic acid be effectively degraded using β-PbO2 reactive electrochemical membrane?

Aqueous perfluorooctanoic acid (PFOA) elimination has raised significant concerns due to its persistence and bioaccumulation. Although β-PbO2 plate anodes have shown efficient mineralization of PFOA, it remains unclear whether PFOA can be effectively degraded using β-PbO2 reactive electrochemical membrane (REM). Herein, we assessed the performance of Ti/SnO2-Sb/La-PbO2 REM for PFOA removal and proposed a possible degradation mechanism. At a current density of 10 mA/cm2 and a membrane flux of 8500 (liters per square meter per hour, LMH), the degradation efficiency of 10 mg/L PFOA was merely 8.8%, whereas the degradation efficiency of 0.1 mg/L PFOA increased to 96.6%. Although the porous structure of the β-PbO2 REM provided numerous electroactive sites for PFOA, the generated oxygen bubbles in the pores could block the pore channels and adsorb PFOA molecules. These hindered the protonation process and significantly impeded the degradation of high-concentration PFOA. Quenching experiments indicated that •OH played dominant role in PFOA degradation. The electrical energy per order to remove 0.1 mg/L PFOA was merely 0.74 Wh/L, which was almost an order of magnitude lower than that of other anode materials. This study presents fresh opportunities for the electrochemical degradation of low-concentration PFOA using β-PbO2 REM.

Cactus-like (Ni,Co)Se2 nanosheets with 3D structure decorated on the conductive substrate for efficient hydrogen evolution reaction

Transition metal selenides are a fascinating class of substitute for traditional noble metal electrocatalysts for hydrogen evolution reaction (HER). However, the monometallic selenides still have the disadvantages of low electroactive sites and electrical conductivity. To address such drawbacks, three-dimensional (3D) hierarchical nanostructures composed of bimetallic compounds have aroused great attention. In this study, cactus-like bimetallic nickel–cobalt nanosheets with a 3D nanostructure are successfully prepared on the surface of conductive substrate by a one-step hydrothermal reaction. Then a high-efficiency bimetallic catalyst ((Ni,Co)Se2/CFP) is obtained by a facile chemical vapor deposition. Benefiting from bimetallic components and the unique 3D structure, the cactus-like (Ni,Co)Se2/CFP only requires a low overpotential of 154 mV to reach the current density of 10 mA cm−2. The Tafel slope of (Ni,Co)Se2/CFP (67 mV dec−1) further shows that (Ni,Co)Se2/CFP has faster HER kinetics. Besides, the long-term stability test demonstrates the excellent durability of (Ni,Co)Se2/CFP in 0.5 M H2SO4. This research offers a useful technique and guide for improving the structure of bimetallic selenides based on transition metals to design high-efficient HER electrocatalysts.

Structural reconstruction of N/S-assisted carbon polyhedral matrix endowed with bimetallic phosphide heterostructures for energy storage

The synergism of heteroatom-doped carbon polyhedral with mixed-metal networks offers a myriad of electroactive sites that aid in excellent capacitive performance. Herein, a simple precipitation method was implemented to synthesis thiourea functionalized bimetallic ZIF-67 polyhedral as a sacrificial template, facilitating the construction of a superior N/S‑carbon matrix with a Co-Ni-P (CNS/CNP) architecture through various thermal phosphorization processes. The CNS/CNP-2 revealed remarkable attributes after phosphorization at 500 °C, including a maximum specific capacitance of 588 F g−1 at a specific current of 1 A g−1 in 3 M KOH electrolyte. This outstanding performance arises from the synergy of N/S carbon matrix, which significantly increases electroactive sites and structural stability, and Co-Ni-P network, which enhances both redox-active site density and conductivity, facilitating rapid ion diffusion. Furthermore, an asymmetrical supercapacitor was integrated as CNS/CNP-2//AC and revealed a maximum specific energy and power of 30.3 W h kg−1 and 12,489 W kg−1, respectively, with capacitance retention of 90% even for 10,000 cycles. The ASC device was designed as a coin-cell to facilitate real-time applications. The study demonstrates that a synergistic effect between CoNi metal ions and a heteroatom matrix can yield an electrode material with a high specific capacity for energy storage devices.

Synthesis of Quaternary (Ni, Co, Cu)Se2 Nanosheet Arrays on Carbon Cloth for Non-Enzymatic Glucose Determination

Unlike transition metal oxides and sulfides, transition metal-based selenides display higher electrical conductivity, more electroactive unsaturated edge sites, and better chemical stability, which have found extensive usage in electrocatalysis. In this work, simple hydrothermal and solvothermal procedures were employed to synthesize quaternary (Ni, Co, Cu)Se2 nanosheet arrays on carbon cloth (CC) to measure glucose. The conductivity of the material can be effectively elevated by adding Se element to form selenides, and the synergistic effect between the three selenides can improve the electrocatalytic performance. Consequently, in the ranges of 0.01–600 μM and 600–9000 μM, respectively, the current response of the synthesized material to glucose concentration exhibited linear relationships. The sensor demonstrated excellent sensitivity and a low detection limit of 5.82 nM. Furthermore, the practical applicability of the constructed biosensor was proved by using it to quantify the amount of glucose in human serum.

Facile Synthesis of Microsphere-like Co0.85Se Structures on Nickel Foam for a Highly Efficient Hydrogen Evolution Reaction.

Microsphere-shaped cobalt selenide (Co0.85Se) structures were efficiently synthesized via a two-step hydrothermal process. Initially, cobalt hydroxide fluoride (Co(OH)F) microcrystals were prepared using a hydrothermal method. Subsequently, Co0.85Se microsphere-like structures were obtained through selenization. Compared to Co(OH)F, the microsphere-like Co0.85Se structure exhibited outstanding catalytic activity for the hydrogen evolution reaction (HER) in a 1.0 M KOH solution. Electrocatalytic experiments demonstrated an exceptional HER performance by the Co0.85Se microspheres, characterized by a low overpotential of 148 mV and a Tafel slope of 55.7 mV dec-1. Furthermore, the Co0.85Se electrocatalyst displayed remarkable long-term stability, maintaining its activity for over 24 h. This remarkable performance is attributed to the excellent electrical conductivity of selenides and the highly electroactive sites present in the Co0.85Se structure compared to Co(OH)F, emphasizing its promise for advanced electrocatalytic applications.

Self-supporting hierarchical porous NiCo2S4/RGO/CNTs nanohybrids with abundant exposed electroactive redox sites for excellent hybrid supercapacitor

Bimetallic sulfide NiCo2S4 is a highly promising electrode material for applications in novel sustainable high-performance energy storage devices, but its poor rate capability and cycling life need to be enhanced. Herein, we report a novel self-supporting hierarchical porous NiCo2S4/RGO/CNTs nanohybrids (NCSRCs) by co-modification of NiCo2S4 nanoparticles with RGO and CNTs. The synergistic effect of RGO and CNTs not only constructs a hierarchical porous conductive network that facilitates charge transport kinetic and ion diffusion kinetic, but also provides abundant induced sites for the dispersion anchoring of NiCo2S4 nanoparticles due to their high specific surface area with rich functional groups, which reduces the stacking of NiCo2S4 nanoparticles and provides abundant exposed electroactive redox sites. Therefore, the electrochemical performance test results demonstrate that the NCSRCs electrodes exhibit significantly enhanced charge storage performance, showing a high specific capacity of 257.1 mAh g−1 at 0.3 A g−1 and good rate capability. In addition, the optimal NCSRC-24//N-RGO aqueous hybrid supercapacitor delivered a high specific energy of 33.67 Wh kg−1 and ultra-long durability with 82.44% capacity retention after 22,000 cycles. These results provide a facile approach to design and synthesize novel NCSRCs nanohybrids with superior properties for high-safety, sustainable and efficient aqueous energy storage devices.

Bifunctional CoxP-FeP@C for overall water splitting realized by manipulating the electronic states of Co via phosphorization

The electronic properties and structural characteristics of transition metal materials have a significant impact on their electrocatalytic performance. Therefore, precisely controlling the electronic states of core metals and fabricating catalysts with advanced structures are conducive to facilitating electrolysis process. Herein, we manipulate the electronic properties of the electroactive sites of catalysts by controlling the degree of phosphorization during the phosphorization process. The CoxP-FeP@C electrocatalysts, characterized by their sea-urchin morphology, were synthesized by subjecting CoFc-metal organic framework (MOF) precursors to phosphorization for specific time intervals. The optimized Co2P-FeP@C-5 electrocatalyst showed the optimum performance towards the oxygen evolution reaction (OER) catalytic efficiency with 239 mV overpotential and the hydrogen evolution reaction (HER) activity with 169 mV overpotential to reach 10 mA·cm−2 in 1.0 M KOH (PH = 13.8).For comparison, the extended duration of phosphorization resulted in the formation of CoP-FeP@C-15 and CoP-FeP@C-30 electrocatalysts, which exhibited compromised electrocatalytic performance due to the transformation of the electroactive core Co2P to CoP during subsequent phosphorization processes.The improved interfacial properties between Co2P and FeP play a crucial role in enhancing the efficiency of water decomposition, attributed to the higher density of states (DOS) at the Fermi Level and the increased availability of electroactive sites for the adsorption of intermediates and electrolysis. These findings are substantiated by density functional theory (DFT) calculations. This approach offers a highly effective means of manipulating the electronic properties of the electroactive transition metal core by controlling the degree of phosphorization, with the ultimate goal of achieving efficient water splitting.

Rapid cold plasma synthesis of cobalt metal–organic framework/reduced graphene oxide nanocomposites for use as supercapacitor electrodes

Metal–organic frameworks (MOFs) are recognized as a desirable class of porous materials for energy storage applications, despite their limited conductivity. In the present study, Co-MOF-71 was fabricated as a high-performance supercapacitor electrode at ambient temperature using a fast and straightforward, one-pot cold plasma method. A supercapacitor electrode based on Co-MOF@rGO was also synthesized by adding reduced graphene oxide (rGO) during processing to increase the capacitance retention and stability after 4000 cycles from 80 to 95.4%. The Co-MOF-71 electrode provided a specific capacitance (Cs) of 651.7 Fg−1 at 1 Ag−1, whereas the Co-MOF@rGO electrode produced a Cs value of 967.68 Fg−1 at 1 Ag−1. In addition, we fabricated an asymmetric device (Co-MOF@rGO||AC) using Co-MOF-rGO as a high-rate positive electrode and activated carbon (AC) as a negative electrode. This hybrid device has a remarkable specific energy and power density. The combination of MOFs with reduced graphene oxide (rGO) in a cold plasma environment resulted in the formation of a three-dimensional nanostructure composed of nanosheets. This nanostructure exhibited an increased number of electroactive sites, providing benefits for energy storage applications.

Constructing metal organic framework derived manganese cobalt layered double hydroxide nanosheets on Ni foam as cost-effective binder-free electrodes of high-performance supercapacitors

A vital aspect of energy storage devices is the development of novel materials with excellent electrical conductivity and rational structures. In combination with alkaline electrolytes, the manganese-cobalt layered double hydroxide (MnCo-LDH) cathode material has long been recognized as a highly desirable cathode material. Nevertheless, the synthesis of MnCo-LDH is time-consuming and required high temperatures. Therefore, it is important to find simple routes for the synthesis of MnCo-LDH. Herein, we propose a synthesis of metal organic framework (MOF)-derived MnCo-LDH nanosheets on conductive nickel foam (NF) for the supercapacitor (SC) application. The CoMOF decorated NF was fabricated by simple precipitation method, and then it was converted to MnCo-LDH by etching process at 80 °C for 5 min (MnCo-LDH/80 °C). The MOF-derived MnCo-LDH/80 °C electrode provides large accessible regions for electrolytes, low charge transfer resistance, and rich electroactive sites. Therefore, the MnCo-LDH/80 °C electrode demonstrates preferable energy storage property with a high areal capacitance of 2.62 F/cm2 at 20 mV/s. In this study, an asymmetric supercapacitor (ASC) is constructed using MnCo-LDH/80 °C and activated carbon (AC) on NF as the positive and negative electrodes, respectively. The optimized MnCo-LDH//AC device provides the maximum energy of 0.116 mWh/cm2 at the maximum power density of 2.49 mW/cm2. Added to that, the ASC has excellent cyclic stability with 78% as the capacitance retention and Coulombic efficiency of 94.3% after 5000 charge-discharge cycles.

Tuning Electrochemical Stability of 5,10-Ditolylphenazine-Based Antiaromatic Materials for Unipolar Memristor toward Artificial Synapses Application.

Three organic conjugated small molecules, DTA-DTPZ, Cz-DTPZ, and DTA-me-DTPZ comprising an antiaromatic 5,10-ditolylphenazine (DTPZ) core and electron-donating peripheral substituents with high HOMOs (-4.2 to -4.7 eV) and multiple reversible oxidative potentials are reported. The corresponding films sandwiched between two electrodes show unipolar and switchable hysteresis current-voltage (I-V) characteristics upon voltage sweeping, revealing the prominent features of nonvolatile memristor behaviors. The numerical simulation of the I-V curves suggests that the carriers generated by the oxidized molecules lead to the increment of conductance. However, the accumulated carriers tend to deteriorate the device endurance. The electroactive sites are fully blocked in the dimethylated molecule DTA-me-DTPZ, preventing the irreversible electrochemical reaction, thereby boosting the endurance of the memristor device over 300 cycles. Despite the considerable improvement in endurance, the decrement of on/off ratio from 105 to 101 after 250 cycles suggests that the excessive charge carriers (radical cations) remains a problem. Thus, a new strategy of doping an electron-deficient material, CN-T2T, into the unipolar active layer was introduced to further improve the device stability. The device containing DTA-me-DTPZ:CNT2T (1:1) blend as the active layer retained the endurance and on/off ratio (∼104) upon sweeping 300 cycles. The molecular designs and doping strategy demonstrate effective approaches toward more stable metal-free organic conjugated small-molecule memristors.

Engineering 2D/2D oxygen vacancy-rich CoAl LDH/rGO sheet-on-sheet heterostructures with improved charge storage for supercapacitors

Layered double hydroxides (LDHs) as electrode materials for supercapacitors still suffer from limited actual specific capacities and unsatisfactory cycling performance owing to their poor intrinsic electrical conductivity and insufficient electroactive sites. Herein, oxygen vacancy (Ov)-rich CoAl-LDH nanosheets are attached onto reduced graphene oxide (rGO) nanosheets to form 2D/2D Ov-CoAl-LDH/rGO sheet-on-sheet heterostructures via a facile precipitation-reduction reaction followed by hydrothermal treatment. The introduction of rich Ov defects in CoAl-LDHs enhances the electrical conductivity, while the attachment of Ov-CoAl-LDH nanosheets on the surface of rGO nanosheets not only reduces the aggregation of Ov-CoAl-LDH nanosheets and thus exposes abundant electroactive sites, but also maintains good structural stability. Theory calculations indicate that the Fermi-level difference of two components triggers interfacial charge separation while creating a built-in electric field at the Ov-CoAl-LDH/rGO interface, which favors rapid electron/ion migration and accelerates charge storage kinetics. The optimized Ov-CoAl-LDH/rGO nanocomposites deliver specific capacities of 984 C g−1 at 3 A g−1 and 708 C g−1 at 20 A g−1 and retain an initial capacity of 90 % after 10,000 cycles at 10 A g−1. These findings showcase a feasible strategy to endow 2D/2D LDHs/graphene heterostructures with enhanced charge storage performance.

The cold plasma synthesis of hierarchical MOF-based nanocomposites with improved electrochemical properties for energy storage devices

Metal-organic frameworks (MOFs) have become known as an attractive group of materials for energy storage applications because of their spectacular characteristics, like porous properties, tunable chemical compositions, and adaptable geometry morphologies. Herein, we produce hierarchical nanostructures based on MOF-71 by using a straightforward one-pot cold plasma method to prepare a high-performance dual Ni/Co-MOF-reduced graphene oxide (Ni/Co-MOF@rGO) material as a supercapacitor electrode. Interestingly, the as-synthesized nanostructure displays a special morphology with superior energy storage capability (3093.72 F g−1 at 1 A g−1). Furthermore, we fabricated an asymmetric device using Ni/Co-MOF@rGO as a high-rate positive electrode and activated carbon (AC) as a negative electrode (Ni/Co-MOF@rGOǁAC). This hybrid device presents an impressive specific energy of 81.82 W h k g−1, a specific power of 2750 W k g−1, and superior cycling stability (94.7% initial capacity retention after 3700 cycles) at a current density of 1 A g−1. The synergistic effect of metal cores and reduced graphene oxide features in a cold plasma atmosphere produced a hierarchical three-dimensional nanostructure with more electroactive sites, which was advantageous for high-efficiency redox processes. This work clearly states the cold-plasma synthesis of MOF nanocomposite with desired morphological characteristics for energy storage applications.

Direct growth of MnCoSe2 nanoneedles on 3D nickel foam for supercapacitor application

The present work reports the fabrication and performance studies of supercapacitors using MnCoSe2 nanoneedles-based electrodes. The MnCoSe2 nanoneedles-based supercapacitor electrode with a unique nanostructure exhibits an enhanced specific capacitance of 820 F g−1 and 386 F g−1 at 1 A g−1 in three-electrode and symmetric two-electrode configurations, respectively. The MnCoSe2 nanoneedles-based supercapacitor device has a specific energy of 54 Wh kg−1 at a specific power of 1 kW kg−1 and a superior cyclic stability of 95% retention after 10,000 charge-discharge cycles at 5 A g−1. Additionally, an asymmetric supercapacitor (ASC) device has been developed employing an anode based on rGO and a cathode based on MnCoSe2 nanoneedles. The asymmetric supercapacitor demonstrates an excellent gravimetric capacitance of 71 F g−1 at 1 A g−1 and an exceptional cycle life of 96% after 10,000 cycles. At a gravimetric power density of 227 W kg−1, the device produces a gravimetric energy density of 32 W h kg−1. The increased electrochemical performance can be ascribed to the three-dimensional nanowire-like surface morphology with a large electroactive site for enhanced redox reaction. Furthermore, high conductivity due to the presence of selenium provides rapid electron transfer and improves the electrochemical properties of supercapacitors. Accordingly, the present work indicates that the MnCoSe2 nanoneedles can be used as a potential electrode material for electrochemical energy storage applications.

Constructing highly stable and biomimetic supercapacitor materials of 2D MoS2 coupled with NiCoLDH @chitosan carbon microsphere

Due to the growing demand for clean and renewable energy, the effective utilization of renewable resources in energy storage and has been concerned. And high specific capacitance and stable electrochemistry for energy storage devices are challenging to develop. Learning from unique structure of goniastrea coral, we design to construct three-dimensional layered conductive electrodes material made of MoS2@chitosan carbon spheres (MNCCS) composite. The NiCoLDH nanosheets construct on the surface of conductive chitosan carbon spheres to effectively form open permeable channels and rich conductive networks, improves the efficient energy storage and electrochemical stability. MoS2 is strongly coupled with NiCoLDH nanosheets through heterointerface, which resembles tentacles on the surface of coral, exposing more active sites to efficiently trap ions. Besides, the obtained material possesses favorable heterojunction interface and defects, which provide sufficient available electroactive sites and numerous storage charge area. Hence, The MNCCS presents an outstanding specific capacitance of 2605.9 F g−1 at 1 A g−1. Notably, a supercapacitor fitted with MNCCS electrode and CCS electrode achieves high specific capacitance (234.4 F g−1 at 1 A g−1), the maximum energy density of 77.0W h kg−1 at highest power density of 667.4W kg−1, along with the excellent cycling stability of 90.8% retention over 10,000 cycles. This work provides a new perspective for fabricating high-performance and stable supercapacitors electrode material for clean energy storage.