Mesoporous Nickel Cobaltite Research Articles

Chemically synthesized mesoporous nickel cobaltite electrodes of different morphologies for high-performance asymmetric supercapacitors

A facile, inexpensive, and template-free strategy has been investigated for the synthesis of nickel cobaltite (NiCo2O4; NCO) for different morphologies on conducting nickel foam using two different complexing agents' ammonia solution (AMM) and hexamethyltetrammine (HMT) and investigated for supercapacitor applications. The nickel cobaltite exhibits a mesoporous structure with pore diameters of 16 and 19 nm and provides a high specific surface area of 150, and 100 m2·g−1 for NCO-AMM and NCO-AMM, respectively. The NCO-HMT electrode exhibit higher specific capacities (2195.8 C·g−1/2744.8 F g−1 at 4 A.g−1) than the NCO-AMM electrode (1579.7 C·g−1/ 1974.6 F g−1 at 4 A. g−1) with high capacity retention ( ̴ 86 %). Excellent cyclic stabilities of 95 and 97 % are obtained from NCO-AMM and NCO-HMT electrodes over 10,000 cycles. A fabricated ASC coin cell (NCO-HMT//rGO) enables a high operation potential window (1.6 V), and an excellent energy density of 60 Wh·kg−1 with a power density of 5500 W·kg−1. The NCO-HMT//rGO also exhibits outstanding cyclic stability of 90 % over 10,000 charge-discharge cycles at 10 A·g−1 current density. This facile synthesis approach provides a superior strategy for producing mesoporous nanomaterials for high-performance ASC.

Oxalic acid assisted rapid synthesis of mesoporous NiCo2O4 nanorods as electrode materials with higher energy density and cycle stability for high-performance asymmetric hybrid supercapacitor applications

In this study, mesoporous nickel cobaltite (NiCo2O4) nanorods as electrode materials for high-performance hybrid supercapacitor were fabricated onto Ni foam by a simple and cost effective oxalic acid (OA) assisted rapid co-precipitation method. The effects of different metal precursors (NCO-Nitrate, NCO-Chloride and NCO-Acetate) on the electrochemical capacitive properties were studied. FE-SEM analysis confirmed that all samples exhibited highly dense mesoporous NiCo2O4 nanorods vertically grown on the surface of Ni foam with excess accessible surfaces and unique sizes and morphologies. The resultant NiCo2O4 nanorod electrodes (for NCO-Nitrate, NCO-Chloride and NCO-Acetate) delivered the maximum specific capacitances of 790, 784, 776 F g−1 at the current density of 1 A g−1 with ultra-high capacitance retention of 82.27, 81.63 and 81.71% even at 20 A g−1 and excellent cyclic stability of 84.25, 83.33 and 83.24% capacitance retention at 5 A g−1 after 5000 cycles. The asymmetric supercapacitor (ASC) device was also sandwiched by using NCO-Nitrate as positive electrode and N-doped graphene hydrogel (NGH) as negative electrode. The fabricated ASC device delivered superior energy density (42.5 W h kg−1) at high power density (746.34 W kg−1) with excellent long cyclic stability (90% initial capacitance retention after 5000 cycles at 5 A g−1).

Solvent-Tuned Synthesis of Mesoporous Nickel Cobaltite Nanostructures and Their Catalytic Properties

In this paper, we prepared mesoporous nickel cobaltite (NiCo2O4) nanostructures with multi-morphologies by simple solvothermal and subsequent heat treatment. By adjusting the solvent type, mesoporous NiCo2O4 nanoparticles, nanorods, nanowires, and microspheres were easily prepared. The as-prepared products were systematically characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) method. Furthermore, the catalytic activities towards the thermal decomposition of ammonium perchlorate (AP) of as-prepared NiCo2O4 nanostructures were investigated.

Microwave-assisted synthesis of porous nickel cobaltite with different morphologies in ionic liquid and their application in supercapacitors

A facile and one-step strategy was used to synthesize one-dimensional (1D) and 2D mesoporous nickel cobaltite (NiCo2O4) rods and sheets, which are conducted in a mixture of ionic liquid and water under microwave irradiation. The as-prepared product electrode exhibited high specific capacitance (879 F g−1 at 0.5 A g−1) and excellent cycling stability (only ca. 4.7% loss after 1500 cycles), suggesting its promising application as an efficient electrode material for supercapacitors. The high performance capacitance is mainly attributed to its binary electroactive surface area of Co and Ni species, and its fast electron and ion transport of the mesoporous structure.

An investigation of the electrochemically capacitive performances of mesoporous nickel cobaltite hollow spheres

Mesoporous NiCo2O4 hollow spheres are prepared by a soft template method utilizing a hydrothermal route. Three kinds of NiCo2O4 morphologies can be obtained, including solid sphere, hollow sphere and collapsed hollow sphere with the adjustment of the concentration of hexamethylenetetramine (HMT). Compared with solid spheres and collapsed hollow spheres, the as-prepared NiCo2O4 hollow spheres show enhanced electrochemical properties, manifesting a high specific capacitance (204.4mAhg−1 at 2Ag−1), exceptional rate capability (62.8% capacity retention at 50Ag−1) and good cycling stability (93.2% capacity retention after 1000 cycles). Such remarkable electrochemical properties of the NiCo2O4 hollow spheres can be primarily ascribed to the high specific surface area and uniform mesoporous hollow structure that can increase the exposure of active sites available for reaction on the surface, shorten transport pathways for both electrons and ions, and alleviate the volume change during charge–discharge process. This work is significant because the unique mesoporous NiCo2O4 hollow spheres demonstrate the great potential in the development of high-performance electrode materials for supercapacitors. Additionally, this soft template method can be extended to the fabrication of other binary or even ternary metal oxides hollow micro-/nanostructure materials.

Mesoporous NiCo2O4 nanoneedles grown on three dimensional graphene networks as binder-free electrode for high-performance lithium-ion batteries and supercapacitors

Mesoporous nickel cobaltite (NiCo2O4) nanoneedles grown on three dimensional graphene networks have been successfully prepared by a facile solvothermal reaction with subsequent annealing treatment. The NiCo2O4/3DGN hybrid is then used as binder-free electrode for high-performance lithium-ion batteries and supercapacitors. The three dimensional graphene based binder-free electrode is considered more desirable than powder nanostructures in terms of shorter Li+ ion diffusion and electron transportation paths, good strain accommodation, better interfacial/chemical distributions and high electrical conductivity. As a result, when used as an anode material for lithium-ion batteries (LIBs), it exhibits high specific discharge capacity as well as superior cycling stability up to 2000 cycles. When it is used for supercapacitor application, this hybrid delivers a high specific capacitance of 970Fg−1 at a high current density of 20Ag−1 with excellent capacitance retention of ∼96.5% after 3000 cycles. Moreover, this synthesis strategy is simple and effective, which could be extended to the construction of other three dimensional graphene based metal oxides hybrid for energy applications.

Novel low temperature synthesis and electrochemical characterization of mesoporous nickel cobaltite-reduced graphene oxide (RGO) composite for supercapacitor application

A simple low temperature method was formulated for the synthesis of mesoporous nickel cobaltite and graphene-nickel cobaltite composite nanoparticles. Self-combustion of urea-nitrate complexant yields high crystalline single phase NiCo2O4 nanoparticles. As expected, graphene prevents the agglomeration of the nanoparticles and restacking of graphene sheets were avoided mutually. FTIR analysis reveals the successful reduction of RGO and composite formation. Qualitative analysis of RGO was obtained from Raman spectrum, which further confirms the composite formation. Chemical purity of the compound was evaluated from XPS studies. Nickel and cobalt ions were found to be in the mixed oxidation state typical of NiCo2O4. Porous morphology of the prepared samples was observed from the FESEM images. BET analysis reveals the significant increase in the specific surface area and mesopores distribution in the composite. Gn-NiCo demonstrates excellent capacitive performance. High specific capacity of 662.3Cg−1 was determined for Gn-NiCo against 485.5Cg−1 exhibited by bare nickel cobaltite at 5mV/s scan rate. Composite material also shows excellent rate characteristics and long cycling stability. This superior performance can be attributed to the porous morphology and high electrical conductivity of graphene sheets. Symmetrical capacitor fabricated using Gn-NiCo electrode material operates within 0–0.8V potential window. Specific capacity of 169.6Cg−1 was obtained in the real capacitor mode. Gn-NiCo prepared by combustion technique is a promising electrode material for supercapacitor applications.

Microwave assisted synthesis of mesoporous NiCo2O4nanosheets as electrode material for advanced flexible supercapacitors

Mesoporous nickel cobaltite (NiCo2O4) nanosheets are synthesized using a cost effective, ultra fast and environmentally friendly microwave assisted heating method followed by a post-calcination process of the as-prepared precursors.

High rate sodium ion battery anodes from block copolymer templated mesoporous nickel–cobalt carbonates and oxides

A soft templating approach enables facile synthesis of ordered mesoporous nickel cobaltite. These materials act as efficient anodes for high rate sodium ion batteries.

Hierarchical mesoporous nickel cobaltite nanoneedle/carbon cloth arrays as superior flexible electrodes for supercapacitors

Hierarchical mesoporous NiCo2O4 nanoneedle arrays on carbon cloth have been fabricated by a simple hydrothermal approach combined with a post-annealing treatment. Such unique array nanoarchitectures exhibit remarkable electrochemical performance with high capacitance and desirable cycle life at high rates. When evaluated as an electrode material for supercapacitors, the NiCo2O4 nanoneedle arrays supported on carbon cloth was able to deliver high specific capacitance of 660 F g-1 at current densities of 2 A g-1 in 2 M KOH aqueous solution. In addition, the composite electrode shows excellent mechanical behavior and long-term cyclic stability (91.8% capacitance retention after 3,000 cycles). The fabrication method presented here is facile, cost-effective, and scalable, which may open a new pathway for real device applications.

Sodium dodecyl sulfate-assisted hydrothermal synthesis of mesoporous nickel cobaltite nanoparticles with enhanced catalytic activity for methanol electrooxidation

Mesoporous nickel cobaltite (NiCo2O4) nanoparticles have been synthesized via a facile hydrothermal strategy with the assistance of sodium dodecyl sulfate (SDS) soft template (ST). Their physicochemical properties have been characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and nitrogen sorption measurements. Their electrocatalytic performances have been examined by cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) tests. The obtained NiCo2O4 materials exhibit a typical nanoscale crystalline hexagonal morphology with specific surface area (SSA) and mesopore volume of 88.63 m2 g−1 and 0.298 cm3 g−1. Impressively, the SDS-assisted NiCo2O4 electrode shows a catalytic current density of 125 mA cm−2 and 72% retention for consecutive 1000 s at 0.6 V in 1 M KOH and 0.5 M CH3OH electrolytes towards methanol (CH3OH) electrooxidation, which is better than the one without SDS assistance. The pronounced electrocatalytic activity is largely ascribed to their higher surface intensities of Co and Ni species and superior mesoporous nanostructures, which provide the richer electroactive sites and faster electrochemical kinetics, leading to the enhanced electrocatalytic activity.

Hydrothermal and soft-templating synthesis of mesoporous NiCo2O4 nanomaterials for high-performance electrochemical capacitors

Mesoporous nickel cobaltite (NiCo2O4) nanoparticles were synthesized via a hydrothermal and soft-templating method through quasi-reverse-micelle mechanism. The physicochemical properties of the NiCo2O4 materials were characterized via X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectra, and nitrogen sorption isotherms measurements. The electrochemical performances of the NiCo2O4 electrode were investigated by cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy tests. The obtained NiCo2O4 materials exhibit typical mesoporous structures, with an average particle size of about 200 nm, a specific surface area of 88.63 m2 g−1, and a total pore volume of 0.337 cm3 g−1. The facile electrolytes penetration for the mesoporous structures favors high-performance of the NiCo2O4 electrode. The NiCo2O4 electrode shows a high specific capacitance (591 F g−1 at 1 A g−1), high-rate capability (248 F g−1 at 20 A g−1), and a good cycling behavior for tested 3,000 cycles, indicating a promising application for electrochemical capacitors.

Ordered mesoporous nickel cobaltite spinel with ultra-high supercapacitance

Mesoporous nickel cobaltite supercapacitor electrodes with ultra-high capacitance were developed by simultaneously tailoring electrode conductivity, pore size dispersion, and crystallinity. High active mass loading (>10 mg cm−2) enables the feasibility for such electrodes being used in practical devices. At a current density of 28.6 A g−1 (equivalent to 10 kW kg−1 power density), the best performance of 8.2 F cm−2 was achieved. The principles illustrated as the motivation of the current work are believed to be able to serve as guidelines for designing future high-performance electrodes.

A facile and cost-effective synthesis of mesoporous NiCo2O4 nanoparticles and their capacitive behavior in electrochemical capacitors

Mesoporous nickel cobaltite (NiCo2O4) nanoparticles were synthesized via a facile and cost-effective ball milling solid-state method and followed by a simple thermal treatment. The physical structures of the materials were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectrum, and Brunauer–Emmett–Teller methods. The electrochemical performances of the materials were investigated by cyclic voltammetry, chronopotentiomerty, electrochemical impedance spectra, and cycling life measurements. The physical characterizations show that the obtained materials consist of nanostructured NiCo2O4 spinels of hexagonal morphology and a spot of nanosized NiO spherical particles and display a layer-stacked mesoporous structure. Electrochemical measurements display that the NiCo2O4 electrode exhibits mainly a Faradaic pseudocapacitive behavior and possesses high performance even after 5,000 cycles with a specific capacitance value of 554 F g−1 at 2 mV s−1 in 1 M KOH electrolytes, a power density and energy density respective value of 2,318 W kg−1 and 5.15 W h kg−1 at a current density of 8 A g−1 in 1 M KOH electrolytes, and an excellent cycling behavior with no capacitance decays and high coulombic efficiency close to 100 % during 5,000 cycles at a current density of 2 A g−1 in 1 M KOH electrolytes, indicating a promising application for electrochemical capacitors.

Ultrathin Mesoporous NiCo2O4 Nanosheets Supported on Ni Foam as Advanced Electrodes for Supercapacitors

AbstractA facile two‐step method is developed for large‐scale growth of ultrathin mesoporous nickel cobaltite (NiCo2O4) nanosheets on conductive nickel foam with robust adhesion as a high‐performance electrode for electrochemical capacitors. The synthesis involves the co‐electrodeposition of a bimetallic (Ni, Co) hydroxide precursor on a Ni foam support and subsequent thermal transformation to spinel mesoporous NiCo2O4. The as‐prepared ultrathin NiCo2O4 nanosheets with the thickness of a few nanometers possess many interparticle mesopores with a size range from 2 to 5 nm. The nickel foam supported ultrathin mesoporous NiCo2O4 nanosheets promise fast electron and ion transport, large electroactive surface area, and excellent structural stability. As a result, superior pseudocapacitive performance is achieved with an ultrahigh specific capacitance of 1450 F g−1, even at a very high current density of 20 A g−1, and excellent cycling performance at high rates, suggesting its promising application as an efficient electrode for electrochemical capacitors.

Facile template-free synthesis of ultralayered mesoporous nickel cobaltite nanowires towards high-performance electrochemical capacitors

In this work, we proposed a facile and scalable template-free strategy to synthesize one-dimensional (1D) ultralayered mesoporous nickel cobaltite (NiCo2O4) nanowires (NWs), which are constructed from lots of quasi-single-crystalline NiCo2O4 nanosheet building blocks. The unique ultralayered mesoporous nanowire electrode exhibited high specific capacitance (401 F g−1 at 1 A g−1), good rate capability (75% capacity retention at 8 A g−1) and excellent cycling stability (only ca. 10% loss after 5000 cycles), exhibiting its great potential application in high-performance electrochemical capacitors as an advanced electrode material. The desirable capacitive performance is mainly attributed to its binary electroactive sites of Co and Ni species, and its intriguing ultralayered mesoporous NWs features.