Interfacial synthesis of micro-cuboid Ni0.55Co0.45C2O4 solid solution with enhanced electrochemical performance for hybrid supercapacitors

Fabrication of composite GO/NiFe2O4-MnFe2O4-CoFe2O4 anode material: Toward high performance hybrid supercapacitors

Here, NiFe2O4, MnFe2O4, and CoFe2O4 nanoferrites are prepared by coprecipitation synthesis technique from nickel, manganese, and cobalt chloride precursors. Synthesized nanoferrites are annealed by calcination process at 800°C for 2 h. To produce a novel anode electrode material for asymmetric supercapacitors (ASCs), the composite material of GO/NiFe2O4-MnFe2O4-CoFe2O4 is fabricated. Physicochemical aspects of the synthesized nanoferrites are evaluated. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy tests are conducted, respectively. The electrochemical activities are studied by cyclic voltammetry, glavanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS) in 2 M KOH as the electrolyte. In three electrode system, the novel GO/NiFe2O4-MnFe2O4-CoFe2O4 electrode displays a high specific capacity of 325 C g-1 and preserves about 99.9% of its initial specific capacity. The GO/NiFe2O4-MnFe2O4-CoFe2O4//GO ASCs device is assembled using GO/NiFe2O4-MnFe2O4-CoFe2O4, GO, and 2 M KOH solution as the positive electrode, negative electrode, and electrolyte, respectively. Significantly, the GO/NiFe2O4-MnFe2O4-CoFe2O4//GO ASCs represent an outstanding energy density of 50.5 W h kg-1 at power density of 2560 W kg-1. Through the long-term charge discharge cycling tests, this ASC device illustrates about 93.7% capacity retention after 3000 cycles. Then, the present study provides the NiFe2O4-MnFe2O4-CoFe2O4 composite nanoferrites as a novel favorable candidate for anode material. RESEARCH HIGHLIGHTS: Simple and green synthesis of magnetic NiCo2O4/NiO/rGO composite nanostructure using natural precursor. Fabricating and designing an efficient semiconductor for degradation ability. NiCo2O4/NiO/rGO nanocomposite with advanced photo elimination catalytic routine. The photocatalytic performance of NiCo2O4/NiO/rGO was surveyed for the degradation of various antibiotics below visible radiation. Efficiency was 92.9% to eliminate tetracycline. We developed a synergetic approach to prepare a novel active material composed of GO/ NiFe2O4-MnFe2O4-CoFe2O4 by a hybrid electrode material. Green synthesis method was accomplished to attain NiCo2O4/NiO/rGO nanocomposite with advanced photo elimination catalytic routine. The oxide nanobundles were prepared with a rapid and eco-friendly method. In order to investigation of the effect of natural precursor, morphology and shape of nanoproducts was compared. NiCo2O4/NiO/rGO nanobundles possess a suitable bandgap in the visible area.

Exploring the potential of CuCoFeTe@CuCoTe yolk-shelled microrods in supercapacitor applications

Driven by their excellent conductivity and redox properties, metal tellurides (MTes) are increasingly capturing the spotlight across various fields. These properties position MTes as favorable materials for next-generation electrochemical devices. Herein, we introduce a novel, self-sustained approach to creating a yolk-shelled electrode material. Our process begins with a metal-organic framework, specifically a CoFe-layered double hydroxide-zeolitic imidazolate framework67 (ZIF67) yolk-shelled structure (CFLDH-ZIF67). This structure is synthesized in a single step and transformed into CuCoLDH nanocages. The resulting CuCoFeLDH-CuCoLDH yolk-shelled microrods (CCFLDH-CCLDHYSMRs) are formed through an ion-exchange reaction. These are then converted into CuCoFeTe-CuCoTe yolk-shelled microrods (CCFT-CCTYSMRs) by a tellurization reaction. Benefiting from their structural and compositional advantages, the CCFT-CCTYSMR electrode demonstrates superior performance. It exhibits a fabulous capacity of 1512 C g-1 and maintains an impressive 84.45% capacity retention at 45 A g-1. Additionally, it shows a remarkable capacity retention of 91.86% after 10 000 cycles. A significant achievement of this research is the development of an activated carbon (AC)||CCFT-CCTYSMR hybrid supercapacitor. This supercapacitor achieves a good energy density (Eden) of 63.46 W h kg-1 at a power density (Pden) of 803.80 W kg-1 and retains 88.95% of its capacity after 10 000 cycles. These results highlight the potential of telluride-based materials in advanced energy storage applications, marking a step forward in the development of high-energy, long-life hybrid supercapacitors.

Nonporous, conducting bimetallic coordination polymers with an advantageous electronic structure for boosted faradaic capacitance

Conductive coordination polymers (c-CPs) are promising electrode materials for supercapacitors (SCs) owing to their excellent conductivity, designable structures and dense redox sites. However, despite their high intrinsic density and outstanding electrical properties, nonporous c-CPs have largely been overlooked in SCs because of their low specific surface areas and deficient ion-diffusion channels. Herein, we demonstrate that the nonporous c-CPs Ag5BHT (BHT = benzenehexathiolate) and CuAg4BHT are both battery-type capacitor materials with high specific capacitances and a large potential window. Notably, nonporous CuAg4BHT with bimetallic bis(dithiolene) units exhibits superior specific capacitance (372 F g-1 at 0.5 A g-1) and better rate capability than isostructural Ag5BHT. Structural and electrochemical studies showed that the enhanced charge transfer between different metal sites is responsible for its outstanding capacitive performance. Additionally, the assembled CuAg4BHT//AC SC device displays a favorable energy density of 17.1 W h kg-1 at a power density of 446.1 W kg-1 and an excellent cycling stability (90% capacitance retention after 5000 cycles). This work demonstrates the potential applications of such nonporous redox-active c-CPs in SCs and highlights the roles of bimetallic redox sites in capacitive performance, which hold promise for the future development of c-CP-based energy storage technologies.

Fabrication of nanosheet-assembled hollow copper-nickel phosphide spheres embedded in reduced graphene oxide texture for hybrid supercapacitors

Owing to their metalloid characteristics with high electrical conductivity, transition metal phosphides (TMPs) have attracted considerable research attention as prospective cathodes for hybrid supercapacitors. Unfortunately, they usually exhibit low rate performance as well as poor longevity, which does not meet the demands of hybrid supercapacitors. The nanocomposite constructed from reduced graphene oxide (rGO) and TMPs with a highly porous nature can effectively overcome the above-mentioned issues, greatly widening their utilization. In this work, we fabricated nanosheet-assembled hollow copper-nickel phosphide spheres (NH-CNPSs) by the controllable phosphatizing of copper-nickel-ethylene glycol (CN-EG) precursors. Then, porous NH-CNPSs were embedded in rGO texture (NH-CNPS-rGO) to form a unique porous nanoarchitecture. The obtained NH-CNPS-rGO has several advantages benefiting as the cathode electrode, such as (i) the hollow structure as well as porous nanosheets are conducive to fast electrolyte diffusion, (ii) the electrical conductivity of NH-CNPS is further enhanced when coupled with the rGO texture, hence promoting electron transfer in the whole structure, (iii) wrapping NH-CNPSs within the rGO texture endows the nanocomposite with much better structural stability, resulting in longer durability of the electrode, And (iv) the porous structures generated in the nanocomposite provide a perfect space for reducing the mass transfer resistance and accessing the electrolyte, thereby boosting the reaction kinetics. The tests demonstrated that the optimal NH-CNPS-rGO electrode revealed a capacity of up to 1075 C g^-1, a superior rate capacity, and exceptional longevity of 94.7%. Moreover, a hybrid supercapacitor (NH-CNPS-rGO‖AC) equipped with the NH-CNPS-rGO-cathode electrode and activated carbon (AC)-anode electrode represented a satisfactory energy density of 64 W h kg^-1 at 801 W kg^-1 and amazing longevity (91.8% retention after 13 000 cycles), which endorses the promising potential of NH-CNPS-rGO for high-efficiency supercapacitors. This research showcases an appropriate method to engineer hollow TMP-rGO nanocomposites as effective materials for supercapacitors.

Synthesis, Characterizations, and Electrochemical Performances of Highly Porous, Anhydrous Co0.5Ni0.5C2O4 for Pseudocapacitive Energy Storage Applications

Electrochemical energy storage relies essentially on the development of innovative electrode materials with enhanced kinetics of ion transport. Pseudocapacitors are excellent candidates to bridge the performance gap between supercapacitors and batteries. Highly porous, anhydrous Ni0.5Co0.5C2O4 is envisaged here as a potential electrode for pseudocapacitor applications, mainly because of its open pore framework structure, which poses inherent structural stability due to the presence of planar oxalate anions (C2O4 2-), and active participation of Ni2+/3+ and Co2+/3+ results in high intercalative charge storage capacity in the aqueous KOH electrolyte. The Ni0.5Co0.5C2O4 electrode shows specific capacitance equivalent to 2396 F/g at 1 A/g in the potential window of 0.6 V in the aqueous 2 M KOH electrolyte by galvanostatic charge/discharge experiments. Predominant pseudocapacitive mechanism seems to operative behind high charge storage due to active participation of Ni2+/3+ and Co2+/3+ redox couple as intercalative (inner) and surface (outer) charges stored by porous anhydrous Co0.5Ni0.5C2O4 were close to high 38 and 62% respectively. Further, in full cell asymmetric supercapacitors (ASCs) in which porous anhydrous Co0.5Ni0.5C2O4 was used as the positive electrode and activated carbon (AC) was utilized as the negative electrode, in the operating potential window 1.6 V, the highest specific energy of 283 W h/kg and specific power of ∼817 W/kg were achieved at 1 A/g current rates. Even at a very high power density of 7981 W/kg, the hybrid supercapacitor still attains an energy density of ∼75 W h/kg with high cyclic stability at a 10 A/g current rate. The detailed electrochemical studies confirm higher cyclic stability and a superior electrochemical energy storage property of porous anhydrous Co0.5Ni0.5C2O4, making it a potential pseudocapacitive electrode for large energy storage applications.

Synthesis, characterizations and electrochemical performances of anhydrous CoC2O4 nanorods for pseudocapacitive energy storage applications

To overcome the environmental challenges caused by utilization of fossil fuel based energy technologies and to utilize the full potential of renewable energy sources such as solar, wind and tidal, high power and high energy density containing large scale electrochemical energy storage devices are a matter of concern and a need of the hour. Pseudocapacitors with accessibility to multiple oxidation states for redox charge transfer can achieve a higher degree of energy storage density compared to electric double layer capacitors (EDLC) and the hybrid supercapacitor is one of the prominent electrochemical capacitors that can resolve the low energy density issues associated with EDLCs. Due to its open pore framework structure with superior structural stability and accessibility of Co^2+/3+/4 redox states, porous anhydrous CoC₂O₄ nanorods are envisaged here as a potential energy storage electrode in a pseudo-capacitive mode. Superior specific capacitance equivalent to 2116 F g^-1 at 1 A g^-1 in the potential window of 0.3 V was observed for anhydrous CoC₂O₄ nanorods in aqueous 2 M KOH electrolyte. A predominant pseudo-capacitive mechanism seems to be operative behind the high charge storage at electrodes as intercalative (Inner) and surface (outer) charge storage contributions were found to be 75% and 25% respectively. Further, in full cell asymmetric supercapacitor (ASC) mode in which porous anhydrous CoC₂O₄ nanorods were used as positive electrodes and activated carbon (AC) was utilised as negative electrodes within an operating potential window of 1.3 V, a highest specific energy of W h kg^-1 and specific power of ∼647 W kg^-1 at 0.5 A g^-1 current density were obtained with superior cycling stability. High cycling stability coupled with superior electrochemical storage properties make anhydrous CoC₂O₄ nanorods potential pseudo-capacitive electrodes for large scale energy storage applications.

Rod-like Ni0.5Co0.5C2O4·2H2O in-situ formed on rGO by an interface induced engineering: Extraordinary rate and cycle performance as an anode in lithium-ion and sodium-ion half/full cells

Transition metal oxalates have attracted wide attention due to the characteristics of the conversion reaction as anode materials in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), However, there are huge volume expansion and sluggish circulation dynamics during the reversible Li⁺ and Na⁺ insertion/extraction process, which would lead to unsatisfactory reversible capacity and stability. In order to solve these problems, a rod-like structure Ni_0.5Co_0.5C₂O₄·2H₂O is in-situ formed on the reduced graphene oxide layer (Ni_0.5Co_0.5C₂O₄·2H₂O/rGO) in a glycol-water mixture medium via an interface induced engineering strategy. Benefitting from the synergistic cooperation of nano-diameter rod-like structure and high conductive rGO networks, the experimental results show that the prepared Ni_0.5Co_0.5C₂O₄·2H₂O/rGO electrode has predominant rate performance and ultra-long cycle stability. For the LIBs, it not only exhibits an ultrahigh reversible capacity (1179.9 mA h g^-1 at 0.5 A g^-1 after 300 cycles), but also presents outstanding rate and cycling performance (646.5 mA h g^-1 at 5 A g^-1 after 1200 cycles). Besides, the Ni_0.5Co_0.5C₂O₄·2H₂O/rGO electrode displays remarkable sodium storage capacity of 221.6 mA h g^-1 after 100 cycles at 0.5 A g^-1. Further, the extraordinary electrochemical capability of Ni_0.5Co_0.5C₂O₄·2H₂O/rGO active material is also reflected in two full-cells, assembled using commercial LiCoO₂ as cathode for LIBs and commercial Na₃V₂(PO₄)₃ as cathode for SIBs, both of which can show wonderful specific capacity and cycling stability. It is found in in-situ Raman experiments that the reversible changes of oxalate peaks are monitored in a charge/discharge process, which is scientific evidence for the transform reaction mechanism of metal oxalates in LIBs. These findings not only provide important ideas for studying the charge/discharge storage mechanism but also give scientific basis for the design of high-performance electrode materials.

Highly porous Co-doped NiO nanorods: facile hydrothermal synthesis and electrocatalytic oxygen evolution properties

Highly porous 3d transition metal oxide nanostructures are opening up the exciting area of oxygen evolution reaction (OER) catalysts in alkaline medium thanks to their good thermal and chemical stability, excellent physiochemical properties, high specific surface area and abundant nanopores. In this paper, highly porous Co-doped NiO nanorods were successfully synthesized by a simple hydrothermal method. The porous rod-like nanostructures were preserved with the added cobalt dopant ranging from 1 to 5 at% but were broken into aggregated nanoparticles at higher concentrations of additional cobalt. The catalytic activity of Co-doped NiO nanostructures for OER in an alkaline medium was assayed. The 5%Co-NiO sample showed a drastically enhanced activity. This result could originate from the combination of advantageous characteristics of highly porous NiO nanorods such as large surface area and high porosity as well as the important role of Co dopant that could provide more catalytic active sites, leading to an enhanced catalytic activity of the nanocatalyst.

Nickel-cobalt oxalate as an efficient non-precious electrocatalyst for an improved alkaline oxygen evolution reaction

The quest for developing next-generation non-precious electrocatalysts has risen in recent times. Herein, we have designed and developed a low cost electrocatalyst by a ligand-assisted synthetic strategy in an aqueous medium. An oxalate ligand-assisted non-oxide electrocatalyst was developed by a simple wet-chemical technique for alkaline water oxidation application. The synthetic parameters for the preparation of nickel-cobalt oxalate (Ni_2.5Co₅C₂O₄) were optimized, such as the metal precursor (Ni/Co) ratio, oxalic acid amount, reaction temperature, and time. Microstructural analysis revealed a mesoporous block-like architecture for nickel-cobalt oxalate (Ni_2.5Co₅C₂O₄). The required overpotential of Ni_2.5Co₅C₂O₄ for the alkaline oxygen evolution reaction (OER) was found to be 330 mV for achieving 10 mA cm_geo ^-2, which is superior to that of NiC₂O₄, CoC₂O₄, NiCo₂O₄ and the state-of-the-art RuO₂. The splendid performance of Ni_2.5Co₅C₂O₄ was further verified by its low charge transfer resistance, impressive stability performance, and 87% faradaic efficiency in alkaline medium (pH = 14). The improved electrochemical activity was further attributed to double layer capacitance (C _dl), which indefinitely divulged the inferiority of NiCo₂O₄ compared to Ni_2.5Co₅C₂O₄ for the alkaline oxygen evolution reaction (OER). The obtained proton reaction order (ρ _RHE) was about 0.80, thus indicating the proton decoupled electron transfer (PDET) mechanism for OER in alkaline medium. Post-catalytic investigation revealed the formation of a flake-like porous nanostructure, indicating distinct transformation in morphology during the alkaline OER process. Further, XPS analysis demonstrated complete oxidation of Ni²⁺ and Co²⁺ centres into Ni³⁺ and Co³⁺, respectively under high oxidation potential, thereby indicating active site formation throughout the microstructural network. Additionally, from BET-normalised LSV investigation, the intrinsic activity of Ni_2.5Co₅C₂O₄ was also found to be higher than that of NiCo₂O₄. Finally, Ni_2.5Co₅C₂O₄ delivered a TOF value of around 3.28 × 10^-3 s^-1, which is 5.56 fold that of NiCo₂O₄ for the alkaline OER process. This report highlights the unique benefit of Ni_2.5Co₅C₂O₄ over NiCo₂O₄ for the alkaline OER. The structure-catalytic property relationship was further elucidated using density functional theory (DFT) study. To the best of our knowledge, nickel-cobalt oxalate (Ni_2.5Co₅C₂O₄) was introduced for the first time as a non-precious non-oxide electrocatalyst for alkaline OER application.

Heterogeneous assembly of Ni-Co layered double hydroxide/sulfonated graphene nanosheet composites as battery-type materials for hybrid supercapacitors

Graphene-based hybrid composites as positive electrodes have aroused great interest in the field of hybrid supercapacitors. However, the charge storage capability of hybrid composites suffers from the scarce interaction between their end members to some extent. Herein, a hybrid composite with electrostatic interaction was obtained by employing a heterogeneous assembly strategy of Ni-Co layered double hydroxide (LDH) and sulfonated graphene nanosheets (SGN). Depending on the substitution of the negatively charged SGN for the interlayer nitrate anions compensating for the positively charged LDH host slabs, the abundance of Ni³⁺ on the surface of the hybrid composite could be increased to intensify the electrostatic interaction within hybrid composites. As expected, the effective coupling of LDH with SGN ensured the uniform incorporation of heterogeneous components. The unique structure of the hybrid composite accelerated electron transfer and ion diffusion processes during electrochemical reactions, which is beneficial to improve the electrochemical performance of battery-type electrodes. Further evaluation showed that the specific capacity of the LDH/SGN hybrid composite is 1177 C g^-1 (2354 F g^-1) at 1 A g^-1. Additionally, the LDH/SGN//AC hybrid supercapacitor achieved an energy density of 43 W h kg^-1 at 800 W kg^-1 and still retained 94% of its initial specific capacitance over 10 000 cycles. The boosting effect of the electrostatic interaction within the hybrid composite on electrochemical properties offers a novel pathway for the development of supercapacitors.

A high-energy-density supercapacitor with multi-shelled nickel-manganese selenide hollow spheres as cathode and double-shell nickel-iron selenide hollow spheres as anode electrodes

Thanks to the attractive structural characteristics and unique physicochemical properties, mixed metal selenides (MMSes) can be considered as encouraging electrode materials for energy storage devices. Herein, a straightforward and efficient approach is used to construct multi-shelled nickel-manganese selenide hollow spheres (MSNMSeHSs) as cathode and double-shell nickel-iron selenide hollow spheres (DSNFSeHSs) as anode electrode materials by tuning shell numbers for supercapacitors. The as-designed MSNMSeHS electrode can deliver a splendid capacity of ∼339.2 mA h g-1/1221.1 C g-1, impressive rate performances of 78.8%, and considerable longevity of 95.7%. The considerable performance is also observed for the DSNFSeHS electrode with a capacity of 258.4 mA h g-1/930.25 C g-1, rate performance of 75.5%, and longevity of 90.9%. An efficient asymmetric apparatus (MSNMSeHS||DSNFSeHS) fabricated by these two electrodes depicts the excellent electrochemical features (energy density of ≈112.6 W h kg-1 at 900.8 W kg-1) with desirable longevity of ≈94.4%.

Understanding the High-Performance Anode Material of CoC2 O4 ⋅2 H2 O Microrods Wrapped by Reduced Graphene Oxide for Lithium-Ion and Sodium-Ion Batteries

Metal oxalate has become a most promising candidate as an anode material for lithium-ion and sodium-ion batteries. However, capacity decrease owing to the volume expansion of the active material during cycling is a problem. Herein, a rod-like CoC₂ O₄ ⋅2 H₂ O/rGO hybrid is fabricated through a novel multistep solvo/hydrothermal strategy. The structural characteristics of the CoC₂ O₄ ⋅2 H₂ O microrod wrapped using rGO sheets not only inhibit the volume variation of the hybrid electrode during cycling, but also accelerate the transfer of electrons and ions in the 3 D graphene network, thereby improving the electrochemical properties of CoC₂ O₄ ⋅2 H₂ O. The CoC₂ O₄ ⋅2 H₂ O/rGO electrode delivers a specific capacity of 1011.5 mA h g^-1 at 0.2 A g^-1 after 200 cycles for lithium storage, and a high capacity of 221.1 mA h g^-1 at 0.2 A g^-1 after 100 cycles for sodium storage. Moreover, the full cell CoC₂ O₄ ⋅2 H₂ O/rGO//LiCoO₂ consisting of the CoC₂ O₄ ⋅2 H₂ O/rGO anode and LiCoO₂ cathode maintains 138.1 mA h g^-1 after 200 cycles at 0.2 A g^-1 and has superior long-cycle stability. In addition, in situ Raman spectroscopy and in situ and ex situ X-ray diffraction techniques provide a unique opportunity to understand fully the reaction mechanism of CoC₂ O₄ ⋅2 H₂ O/rGO. This work also gives a new perspective and solid research basis for the application of metal oxalate materials in high-performance lithium-ion and sodium-ion batteries.

Hierarchical ultrathin defect-rich CoFe2O4@BC nanoflowers synthesized via a temperature-regulated strategy with outstanding hydrogen evolution reaction activity

Graphical illustration of the synthesis and the electrocatalytic performance of CoFe₂O₄@BC 500 °C nanoflowers.

Design of nickel cobalt molybdate regulated by boronizing for high-performance supercapacitor applications

Nickel-cobalt-based molybdates have been intensively investigated because of their high theoretical specific capacitance and multifarious oxidation states. Here, we have successfully synthesized hierarchical structures (Ni₃B/Ni(BO₂)₂@Ni_xCo_yMoO₄) by boronizing Ni_xCo_yMoO₄ nanosheets on flexible carbon cloth substrates. Benefitting from the synergistic effect among Ni₃B, Ni(BO₂)₂ and Ni_xCo_yMoO₄ in hybrid architectures, the electrode material possesses higher capacity of 394.7 mA h g^-1 at 1 A g^-1 and a good rate performance (309.5 mA h g^-1 maintained at 20 A g^-1). Then, a hybrid supercapacitor assembled with Ni₃B/Ni(BO₂)₂@Ni_xCo_yMoO₄ and activated carbon as the positive and the negative electrode, displays a high specific capacitance of 370.7 F g^-1 at 1 A g^-1 (210 F g^-1 at 10 A g^-1), a high voltage of 1.7 V, and a high energy density of 131.8 W h kg^-1 at the power density of 800 W kg^-1 (still 74.7 W h kg^-1 maintained at 8000 W kg^-1). This study widens the research scope of boronizing pseudocapacitance materials and reveals a high application potential of Ni₃B/Ni(BO₂)₂@Ni_xCo_yMoO₄ for energy storage devices in the future.

Novel Two-Dimensional Porous Materials for Electrochemical Energy Storage: A Minireview

Two dimensional (2D) porous materials have great potential in electrochemical energy conversion and storage. Over the past five years, our research group has focused on Simple, Mass, Homogeneous and Repeatable Synthesis of various 2D porous materials and their applications for electrochemical energy storage especially for supercapacitors (SCs). During the experimental process, through precisely controlling the experimental parameters, such as reaction species, molar ratio of different ions, concentration, pH value of reaction solution, heating temperature, and reaction time, we have successfully achieved the control of crystal structure, composition, crystallinity, morphology, and size of these 2D porous materials including transition metal oxides (TMOs), transition metal hydroxides (TMHOs), transition metal oxalates (TMOXs), transition metal coordination complexes (TMCCs) and carbon materials, as well as their derivatives and composites. We have also named some of them with CQU-Chen (CQU is the initialism of Chongqing University, Chen is the last name of Lingyun Chen), such as CQU-Chen-Co-O-1, CQU-Chen-Ni-O-H-1, CQU-Chen-Zn-Co-O-1, CQU-Chen-Zn-Co-O-2, CQU-Chen-OA-Co-2-1, CQU-Chen-Co-OA-1, CQU-Chen-Ni-OA-1, CQU-Chen-Gly-Co-3-1, CQU-Chen-Gly-Ni-2-1, CQU-Chen-Gly-Co-Ni-1, etc. The introduction of 2D porous materials as electrode materials for SCs improves the energy storage performances. These materials provide a large number of active sites for ion adsorption, supply plentiful channels for fast ion transport and boost electrical conductivity and facilitate electron transportation and ion penetration. The unique 2D porous structures review is mainly devoted to the introduction of our contribution in the 2D porous nanostructured materials for SC. Finally, the further directions about the preparation of 2D porous materials and electrochemical energy conversion and storage applications are also included.

Redox Tuning in Crystalline and Electronic Structure of Bimetal-Organic Frameworks Derived Cobalt/Nickel Boride/Sulfide for Boosted Faradaic Capacitance

The development of efficient electrode materials is a cutting-edge approach for high-performance energy storage devices. Herein, an effective chemical redox approach is reported for tuning the crystalline and electronic structures of bimetallic cobalt/nickel-organic frameworks (Co-Ni MOFs) to boost faradaic redox reaction for high energy density. The as-obtained cobalt/nickel boride/sulfide exhibits a high specific capacitance (1281 F g^-1 at 1 A g^-1 ), remarkable rate performance (802.9 F g^-1 at 20 A g^-1 ), and outstanding cycling stability (92.1% retention after 10 000 cycles). An energy storage device fabricated with a cobalt/nickel boride/sulfide electrode exhibits a high energy density of 50.0 Wh kg^-1 at a power density of 857.7 W kg^-1 , and capacity retention of 87.7% (up to 5000 cycles at 12 A g^-1 ). Such an effective redox approach realizes the systematic electronic tuning that activates the fast faradaic reactions of the metal species in cobalt/nickel boride/sulfide which may shed substantial light on inspiring MOFs and their derivatives for energy storage devices.