Ni-Co Double Hydroxide Research Articles

Highly dispersive nickel vanadium oxide nanoparticles anchored on nickel cobalt phosphate micron-sheets as cathodes for high-energy hybrid supercapacitor devices

The effective strategies of customizing suitable orientation and rationalizing structures are significant for developing high-performance energy storage materials applied in supercapacitors, which are regarded as promising clean energy storage devices. To obtain highly efficient MOF (metal-organic framework)-derived phosphate electrode, it is necessary to combine it with highly conductive materials for a synergistical effect. So, in this work, the Ni-Co DH (double hydroxide) is used as sacrificial template to prepare MOF through a reverse strategy, which makes a foundation for shaping anisotropic orientation to impede structural stack. The Ni3V2O8 nanoparticles are dispersedly anchored on NiCo-P micron-sheet through a conversion from nanostructured MOF/Ni3V2O8. The evolution in structural size avoids agglomeration of Ni3V2O8 nanoparticles, which also leads to shaggy and intact NiCo-P micron-sheets, thereby improving fully contact with electrolyte. As a result, the obtained NiCo-P/Ni3V2O8 with abundant electroactive sites and valences displays extraordinary specific capacitance of 2520 F g−1 (1134 mA h g−1) at 1 A g−1 with capacitance retention of 89.05 % even when the current density increases to 10 A g−1. The NiCo-P/Ni3V2O8 and AC as cathode and anode, respectively, are assembled into a hybrid supercapacitor (HSC) device to fulfil requirement for high-performance supercapacitor devices. As-made NiCo-P/Ni3V2O8//AC HSC delivers preeminent specific energy density (SE) of 65 Wh Kg−1 at specific power density (SP) of 750 W Kg−1.

Preparation and electrochemical performance of PPyNTs/NiCo-LDH for asymmetric supercapacitors

Supercapacitors possess remarkable benefits in terms of electrochemical energy storage, whereas the inherent defects, such as suboptimal power density, limit commercial employment. Here, NiCo double hydroxide (NiCo-LDH) nanosheets with ZIF-67 as the precursor were fabricated and anchored on the surface of polypyrrole nanotubes (PPyNTs) to prepare composite electrode materials (PPyNTs/NiCo-LDH). Electrochemical test results show that the electrode material possesses 1802 F g−1 specific capacitance under a 1 A g-1 current density. Furthermore, it shows a retention of 50.2 % for capacitance after 5000 cycles with 10 A g-1 current density. To examine the practical performance of the materials, aqueous asymmetric supercapacitors PPyNTs/NiCo-LDH//AC were assembled, with up to 115 F g−1 specific capacitance at 1 A g-1 under a stabilized output voltage of 1.5 V, and possessing a high energy density of 35.94 Wh kg−1 at a power density of 760.2 W kg−1. Meanwhile, the capacitance retention of 65.3 % after 5000 cycles.

Developing a high-performance hybrid supercapacitor with the controlled assembly of a hierarchical 3D flower-like NiCo double hydroxide nano/microarchitecture electrode material

The design of hierarchical nano/microarchitectures containing multiple elemental compositions has attracted significant interest due to their ability to offer morphological, enhanced conductive, and exceptional electrochemical capabilities in the field of energy storage. Herein, a 3D flower-like porous nano/microarchitecture of NiCo double hydroxide (NCDH-1) was synthesized using a facile hydrothermal technique for supercapacitor electrode materials. The 3D hierarchical structure formed by the network arrangement of 2D nanosheets comprises of many open spaces between the nanosheets. These nanosheets lead to a large specific surface area, abundant active sites, and multiple channels for the transport of electrons/ions. These factors boost redox processes and facilitate the rapid transfer of electrons/ions into the electrode material. The NCDH-1 electrode material, with its hierarchical 3D nano/microarchitecture, exhibits the supreme capacitance (Csp) of 2199 F g−1 at 1 A g−1 and demonstrates excellent rate capability, retaining 58.2 % at 20 A g−1. The hybrid supercapacitor configured using 3D flower-like NCDH-1 and commercial grade activated carbon (AC; MSP-20) electrodes demonstrates an impressive Csp of 232 F g−1 at 1 A g−1, a superior energy density of 72.5 Wh kg−1, and an excellent cycle lifetime. Thus, the approach outlined in this work offers a promising strategy for developing 3D nano/microarchitecture metal hydroxides with potential applications in energy storage systems.

Electrodepositing NiCo-double hydroxides with high electrochemical performance by adjusting the rheological behavior of electrolyte

Electrodeposition is a facile and convenient method to prepare NiCo double hydroxides for binder-free electrode materials that are equipped with superior electrochemical performance. But the samples synthesized by electrodeposition exhibit monotonous nanosheets array morphology and poor durability. In this paper, we proposed a novel electrodeposition way by introducing a water-soluble polymer, i.e. polyacrylamide (PAM) with different molecular weights (Mw) into the electrolyte to manipulate the morphology and electrochemical property. By adjusting the rheological behavior of the electrolyte, the NiCo hydroxides with different morphology can be acquired as the active materials can grow along the soft template constructed by polymer chains. The morphology of the active materials varies along with the concentration and molecular weight of the polymer as well. Furthermore, amorphous phases are accompanied by the crystal during the deposition. Benefit from the unique multilevel morphology and high specific surface area, the electrodes synthesized at the electrolyte containing an appropriate concentration of polymer exhibit higher specific capacitance and longer cycling performance than that prepared in the pure water system. This work provides a novel strategy to prepare double hydroxides with diverse morphology and electrochemical performance.

Sulfidation of ZIF-Derived Core-Shell NiCo LDH/Ni MOF Heterostructure toward Supercapacitor Electrodes with Enhanced Performance

Developing electrodes in a reasonable structure is essential to boost the performance of supercapacitors. Self-supporting heterostructures enriched active sites are promising as binder-free electrodes for supercapacitors. Here, core-shell layered double hydroxide (LDH)/Metal organic frame (MOF) heterostructure was directly grown on carbon cloth (CC) substrate derived from L-Co ZIF NWAs. Subsequently, the composite was treated with a sulfidation process to optimize its electrical conductivity. Thanks to its unique network structure, it facilitates active site exposure and efficient charge transfer, together with the synergetic effect between NiCo double hydroxide and Ni MOF nanosheets. This hybrid electrode possesses an excellent specific capacity (1200 F g−1 at 1 A g−1) and stable cycle performance with 86% capacity maintained after 4000 cycles, indicating its potential superiority for use in high-efficiency electrochemical capacitors.

Electrode made of NiCo double hydroxide on oxidized activated carbon for asymmetric supercapacitors

NiCo double hydroxide (NiCo-DH) and oxidized activated carbon (OAC) were used to synthesize a three-dimensional (3D) NiCo-DH@OAC via hydrothermal method. OAC acts as the support for in-situ growth of NiCo-DH nanowires, and oxygen-containing groups on the surface of OAC are crucial for the uniform loading of NiCo-DH and keeping structural stability of the composites. Due to the synergistic effect between NiCo-DH and OAC, NiCo-DH@OAC presents an excellent specific capacitance (1990 F g−1 at 1 A g−1). The asymmetric supercapacitor (ASC) is assembled with NiCo-DH@OAC as the positive electrode and OAC as the negative electrode, and exhibits a superior energy density (46.5 Wh kg−1 at 800 W kg−1) and a cycling stability (90.7% after 10,000 cycles). Furthermore, ASC has been demonstrated effective in solar panel integrated supercapacitors.

An Unveiled Electrocatalysis Essence of NiCo Hydroxides through in Situ Raman Spectroscopy for Urea Oxidation

The electrochemical urea oxidation reaction (UOR) is the performance‐limiting half reaction of urea electrolysis for producing renewable hydrogen energy. Nevertheless, the essence of electrode function mechanism of catalysts remains unclear. Therefore, design and optimization of catalysts are restricted. Herein, an in situ Raman spectroscopy method is employed to directly measure the electrode properties of the NiCo double hydroxides (NiCo DHs) under working conditions. Given definitely evidence, the evolution process of in situ Raman spectra shows that the Ni element is converted to NiOOH under UOR potentials, while the Co dopant is converted to CoOOH and further to higher‐valence CoO2 species. Obviously, the catalytically active phase toward UOR is really a complex NiOOH–CoOOH–CoO2 phase. Accurately matched spectral wavenumbers and electrochemical measurements of the catalytic electrodes explicitly reveal that the addition of Co assuredly reduces the onset potential for electroactive NiOOH formation. The Raman results also indicate effects of the NiO bond elongation and increased disorder caused by Co doping. Herein, an important understanding and new mechanistic perspectives for the electrode reaction process of UOR with NiCo binary catalysts are provided.

Highly Stable Nico Double Hydroxide @Oxidation Modification Activated Carbon for High-Performance Asymmetric Supercapacitors

Highly Stable Nico Double Hydroxide @Oxidation Modification Activated Carbon for High-Performance Asymmetric Supercapacitors

Electrochemical investigation of NiCo double hydroxides for supercapacitors

NiCo-layered double hydroxides (NCLDH) synthesized by a simple one pot sol–gel process using propylene oxide as gelation agent. Synthesized material is investigated for its crystal structure, morphology including specific surface area and electrochemical performance as supercapacitor electrodes. The specific capacitance of as-synthesized NCLDH is 1166F/g, when the electrodes undergone charge/discharge cycling in 6 M potassium hydroxide at 1 A/g specific current. Enthrallingly, retention of capacity over 1000 and 2000 cycles found up to correspondingly 80% and 64%, at relatively high 30 A/g specific current. High capacity is ascribed to uniform porous nature of the material with considerable surface area. With an appreciable cycle life and charge storage capacity, the material prepared is an able contender for supercapacitor electrodes.

NCoCu Carbon Dots Intertwined NiCo Double Hydroxide Nanorod Array for Efficient Electrocatalytic Hydrogen Evolution

AbstractElectrocatalytic production of hydrogen from water is a faster and environmentally friendly way of producing bulk hydrogen with the highest purity. Herein, a highly efficient mesh‐like cobalt hydroxide self‐supporting catalyst coupled with NCoCu‐5 carbon dots (CDs) on Ni foam (NF) is reported by a common hydrothermal way. The type of carbon dots on NiCo double hydroxide has a great effect on the morphology of the catalyst (NCoCu‐5 CDs/NF−CoNi). The intertwined mesh‐like NCoCu‐5 CDs/NF−CoNi catalyst has an excellent HER performance, exhibiting a low overpotential of 65 mV at 10 mA cm−2. After coupling with NCoCu‐5 CDs, a new Co−N electronic transfer channel is created in composite, and a suitable electronic environment is produced between Co and NCoCu‐5 CDs. Copper cations react with NF to generate Cu+ intermediate ions, thus further promoting the formation of Co3+. It supplies a high‐speed charge channel for the transmission of ions and increases the active sites.

Multilayered and hierarchical structured NiCo double hydroxide nanosheets generated on porous MgCo2O4 nanowire arrays for high performance supercapacitors

In this work, MgCo2O4@NiCo layered double hydroxide (LDH) hierarchical structure nanocomposites on Ni foam (NF) are synthesized by facile hydrothermal and calcination methods. MgCo2O4/NF is synthesized first via a hydrothermal reaction and annealing treatment and then utilized to prepare MgCo2O4@NiCo-LDH/NF hierarchical structure nanocomposites via the second hydrothermal process. It is found that the MgCo2O4@NiCo-LDH/NF nanocomposite prepared from 9 h hydrothermal reaction (MC@NC-LDH-2) exhibits an excellent specific capacitance of 5701.2 F g−1 at the current density of 1 A g−1. Moreover, a high capacitance retention (83.7% maintained after 5000 cycles) and a low internal resistance (Rs) (0.783 Ω) can be achieved. Furthermore, a quasi-solid state asymmetric supercapacitor (ASC) is assembled using MgCo2O4@NiCo-LDH/NF-2 as positive electrode and activated carbon (AC) as negative electrode. The as-fabricated MgCo2O4@NiCo-LDH/NF-2//AC ASC shows a high energy density of 89.79 Wh kg−1 at 800 W kg−1. Meanwhile, the MgCo2O4@NiCo-LDH/NF-2//AC ASC device possesses an excellent cycling stability of 89.03% retention of the initial capacitance after 5000 cycles and two ASC devices connected in series can light up a LED bulb for 15 min. Our results manifest that these hierarchical MgCo2O4@NiCo-LDH composites could envision huge potential application in energy storage devices.

Acetamide-assisted hydrothermal growth of NiCo double hydroxide on graphene modified Ni foam for high-performance supercapacitor

The free-standing hierarchical flower-like NiCo-double hydroxide/reduced graphene oxide composite (NiCo-DH/RGO) on Ni foam (NiF) was synthesized with a facile two-step method. First, the growth of partially reduced graphene oxide (PRGO) membrane on NiF was achieved via the direct reduction of graphene oxide (GO) by NiF, which acted as not only the reducing agent but also the current collector. Then, the growth of high mass-loading NiCo-DH on PRGO/NiF was realized with a hydrothermal process, in which acetamide plays a crucial role. The high mass-loading of NiCo-DH is due to the addition of acetamide into the hydrothermal bath, in which PRGO reacted with the solution, containing Ni(II), Co(II), acetamide and urea, to form a thick gelatinous membrane on Ni foam. During the hydrothermal process, PRGO was further reduced to RGO while both Ni(II) and Co(II) reacted with ammonium, released by the hydrolysis of urea, to form NiCo-DH. Used as the positive electrode of supercapacitor, NiCo-DH/RGO/NiF displays an ultrahigh areal capacity of 6.15 C cm−2 at 10 mA cm−2 and 94.6% capacity retention after 1000 GCD cycles at 10 mA cm−2. An asymmetric supercapacitor (ASC) is also assembled with NiCo-DH/rGO/NiF as the positive electrode and activated carbon (AC) as the negative electrode. The ASC exhibits a prominent energy density of 61.81 Wh kg−1 at a high power density of 842.63 W kg−1. It is especially worth noting that the ASC exhibited remarkable capacity retention of 84.53% even after 1000 GCD cycles at a current density of 10 mA cm−2.

Ni-Co Double Hydroxide Grown on Graphene Oxide for Enhancing Lithium Ion Storage

It still remains a major challenge to maintain the excellent lithium ion-storage performance of layered double hydroxide (LDH) for lithium ion battery anodes at high current density and long cycle ...

Heterojunction induced activation of iron oxide anode for high-power aqueous batteries

Aqueous Ni-Fe batteries show promise for grid level energy storage due to their high safety and low cost. However, high capacities of Fe-based anodes can only be achieved under slow discharging rates. Moreover, an activation process is often required, the mechanism of which has not been fully understood. Herein, we present a facile and controllable method to uniformly deposit Fe3O4 nanoparticles on a 3D graphite substrate. Post-mortem analysis demonstrates the partial conversion of Fe3O4 to FeOOH during the subsequent in-situ electrochemical activation process, forming a Fe3O4/FeOOH heterostructure. Density functional theory calculations suggest that a built-in electric field is formed near the Fe3O4/FeOOH interface, which facilitates the charge transfers and lowers the adsorption energy of OH−. The above modification on the active material significantly improves its electrochemical activity. The activated electrode delivers a high capacity of 509 mAh g−1 at the ultra-high current density of 100 A g−1. A Ni-Fe cell assembled with activated Fe3O4/FeOOH anode and Ni-Co double hydroxide cathode provides a high energy density of 161.3 Wh kg−1 and a maximum power density of 43 kW kg−1, making it a good candidate for high safety, low cost, and environmental friendliness energy storage systems.

The composite of 3D carbon nanotube architecture and NiCo double hydroxide for high-performance supercapacitor

A three-dimensional porous architecture of multiwalled carbon nanotubes (MWCNT), denoted as 3D-MWCNT, was fabricated on Ni foam (NiF) via a simple hydrothermal method. The 3D-MWCNT, constructed with interlaced carbon nanotubes, is a highly porous network structure and is subsequently used as the electrical conductive platform for the fabrication of positive electrode of faradaic supercapacitor. The obtained positive electrode was denoted as NiCo-DH/3D-MWCNT/NiF, which was produced via the electrodeposition of NiCo double hydroxide (NiCo-DH) on 3D-MWCNT/NiF. The 3D-MWCNT platform not only endows NiCo-DH/3D-MWCNT/NiF large surface area but also enhanced electrical conductivity. NiCo-DH/3D-MWCNT/NiF displays an ultrahigh areal capacity of 6.142 C cm−2 at 60 mA cm−2 and 96.31% capacity retention after 2000 cycles at 60 mA cm−2. An asymmetrical supercapacitor (ASC) is also assembled with NiCo-DH/3D-MWCNT/NiF as the positive electrode and activated carbon (AC) as the negative electrode. The ASC exhibits a prominent specific energy of 30.99 Wh kg−1 at a high specific power of 427.46 W kg−1. It is especially worth noting that the ASC exhibited remarkable capacity retention of 84.7% even after 2000 galvanostatic charge–discharge cycles at a high current density of 30 mA cm−2.

Hierarchical nanoflake-assembled flower-like NiCo double hydroxide@NiC2O4 microspheres for high-performance supercapacitor

ABSTRACTAssembly of NiCo double hydroxide@NiC2O4 porous microspheres on Ni foam was fabricated by the direct anodisation of nickel foam (NF) and the subsequent electrodeposition of NiCo double hydroxide (NiCo-DH). The obtained Ni foam-supported NiCo-DH@NiC2O4 (NiCo-DH@NiC2O4/NF) was used as the binder-free electrode for electrochemical capacitor (EC). The combination of NiC2O4 and NiCo-DH increases the amount of active sites for redox reactions while the hierarchical porous morphology significantly enhances the diffusion of electrolyte. With Ni foam as 3D conductive substrate and current collector, the electronic conductivity of the electrode material was significantly improved and the diffusion of the electrolyte on the electrode surface was effectively enhanced. NiCo-DH@NiC2O4/NF demonstrates a high areal capacity, a good cycling stability and a good rate capability . In addition, a hybrid supercapacitor (HSC) assembled with NiCo-DH@NiC2O4/NF as the positive electrode and activated carbon (AC) as the negative electrode exhibited good performance with high energy density and power density.

Facile Synthesis of Ni-Co Double Hydroxide on Carbonized Cotton Cloth for High Performance Supercapacitor

Facile Synthesis of Ni-Co Double Hydroxide on Carbonized Cotton Cloth for High Performance Supercapacitor

Microwave-power-enabled tuning of NiCo double hydroxide nanostructures

Microwave heating has been widely used to enhance the fabricating rate of nanomaterials in the past few decades. However, the application of interaction between microwave and chemical reaction in tuning nanomaterials morphology is yet to be explored, while strategies to manipulate material nanostructures are of great importance for enhanced function. In this work, we demonstrate the potential of microwave in tuning the morphology of nanostructured NiCo DHs by accurate temperature control through the precise design of microwave reacting system. We find that 200-W microwave irradiation gives yield to unique flower-on-sheet hierarchical structure of NiCo DHs, while microspheres are derived from oil-bath heating. Microwave power is found to play a vital role in the tuning process. When microwave power decreases to 50 W, assembled nanoflakes are obtained; when microwave power increases to 300 W, microspheres are obtained. Further, fluid permittivity is monitored and field intensity in the reacting region is simulated and found to increase with time. Taken together, it is proposed that field-induced de-solvation possibly exists and is the main tuning mechanism. When tested as electrode materials in supercapacitor, products obtained from 200 W microwave treatment show enhanced storage capacities, especially at high current density.

Hierarchical Ni–Co double hydroxide nanosheets on reduced graphene oxide self-assembled on Ni foam for high-energy hybrid supercapacitors

This work presents a novel method for the self-assembly of reduced graphene oxide (rGO) on nickel foam (NF) and the subsequent electrodeposition of hierarchical Ni-Co double hydroxide (NiCo-DH) nanosheets (NS) on rGO as a supercapacitor electrode. The self-assembly of rGO on NF is achieved by the direct reduction of graphene oxide at 50 °C. NF is not only used as the support of rGO but also the reducing agent for the reduction of GO. As the battery-type electrode material for supercapacitor, NiCo-DH supported on rGO modified NF (Ni-Co DHNS@rGO-NF) displays an ultrahigh areal capacity of 5.820 C cm−2 at 20 mA cm−2, a 100% coulombic efficiency and a 78% capacity retention after 2000 cycles at 100 mA cm−2. An hybrid supercapacitor (HSC) is also assembled based on Ni-Co DHNS@rGO-NF as the positive electrode and active carbon (AC) as the negative electrode. The ASC exhibits a prominent energy density of 45.83 Wh kg−1 at a high power density of 396.15 W kg−1. The excellent electrochemical performance is attributed to the large surface area of the hierarchical NiCo-DH nanosheets array and the synergistic effect between Ni-Co DHNS and rGO.

Morphology engineering of electro-deposited iron oxides for aqueous rechargeable Ni/Fe battery applications

Aqueous rechargeable Ni/Fe batteries possess potential advantages for large-scale energy storage applications due to their low cost, high safety and fast ion diffusions in electrolyte. However, the electrochemical performance of the iron-based anode is still far from ideal due to particle aggregations. Herein, we carry out the morphology engineering on the iron oxide active materials via a facile electrochemical method to improve its charge storage capability. The morphology transition from zero-dimensional particles to one-dimensional nanorods is realized by tuning the electrolyte composition, while subsequent annealing treatment results in further morphology modification into 3D interconnected nanoparticles (10–20 nm). The hierarchical structure allows facile ion and electron transfers, and the large surface provides various active sites for the charge storage conversion reaction. As a result, even at the high current density of 2 A g−1 (∼6C rate), the iron oxide electrode can still deliver a high specific capacity of 184 mAh g−1. At the same time, the morphology integrity and stability of the electrode leads to a good cycle life, with 87.5% capacity retained upon 5000 cycles. The Ni/Fe full cell assembled with the iron oxide anode and a Ni-Co double hydroxide cathode exhibits a good energy density of 82.3 Wh kg−1 at the power density of 3.3 kW kg−1. Our fundamental study would provide new insights for the electro-deposition of iron-based materials and endow new opportunities for the fabrication of high-performance iron-based electrodes for energy storage systems.