NiCo-layered Double Hydroxide Research Articles

Facile syntheses of Fe2O3-rGO and NiCo-LDH-rGO nanocomposites for high-performance electrochemical capacitors

Faraday-type electrode materials and devices for electrochemical capacitors have been widely investigated. However, their applications are severely limited by the preparation method and cost of electrode materials. In this work, high-performance electrochemical capacitors were successfully assembled using Fe2O3-decorated reduced graphene oxide (rGO) nanocomposites and NiCo-Layered Double Hydroxides (LDH) as the anode and cathode, respectively. An easy and efficient approach (the modified precipitation method) for the large-scale fabrication was used to prepare Fe2O3 and NiCo-LDH, supported by rGO sheets, respectively. The anode material, Fe2O3-rGO, exhibited an excellent specific capacitance (Csp) of 1073 F g−1 at a current density of 1 A g−1 and a retention rate of 92 % at 10 A g−1, while the NiCo-LDH-rGO cathode material provided a Csp of 1850 F g−1 at 1 A g−1 and maintained 84 % at 10 A g−1. The effective combination of these electrodes for the NiCo-LDH-rGO//Fe2O3-rGO electrochemical capacitors resulted in an excellent energy density of 108 Wh/kg at a power density of 884 W/kg, with remarkable cycling stability (80 % after 1000 cycles at 10 A g−1). We believe that this work, including the proposed method and electrode materials, will advance the further development and commercialization of electrochemical capacitors.

Nickel–cobalt layered double hydroxide/NiCo2S4/g-C3N4 nanohybrid for high performance asymmetric supercapacitor

Graphitic carbon nitride (g-C3N4) with semiconducting nature can be considered for energy storage system by modifying its electrical conductivity and structural properties through formation of hybrid with materials such as bimetallic metal sulfide and nickel-cobalt layered double hydroxide (LDH). g-C3N4 as a N-rich compound with basic surface sites can change the surface properties of nanohybrid and impress the charge transfer. In this study, a nanohybrid based on nickel-cobalt LDH and sulfide and graphitic carbon nitride (NiCo LDH/NiCo2S4/g-C3N4) was synthesized through a three-step method. At first, Ni doped ZIF-67 was formed at the surface of g-C3N4 nanosheets and then the product was calcined in a furnace to form NiCo2O4/g-C3N4. At next step, the sample was hydrothermally converted to NiCo2S4/g-C3N4 using thioacetamide and finally modified with NiCo LDH nanoplates to form porous structure with high surface area. The NiCo LDH/NiCo2S4/g-C3N4 nanohybrid showed high specific capacitance of 1610 F g−1 at current density of 1 A g−1 and also excellent stability of 108.8% after 5000 cycles at potential scan rate of 50 mV s−1, which makes it promising candidate for energy storage. An asymmetric system was prepared using nickel foams modified with NiCo LDH/NiCo2S4/g-C3N4 and g-C3N4 as positive and negative electrodes, respectively. The specific capacitance of 246.0 F g−1 was obtained at 1 A g−1 in 6 M KOH solution and system maintained 90.8% cyclic stability after 5000 cycles at potential scan rate of 50 mV s−1. The maximum energy density and power density of the system were calculated as 82.0 Wh kg−1 and 12,000 W kg−1, respectively, which demonstrate its capability for energy storage.

Heterostructure tailoring of carbon nanotubes grown on prismatic NiCo clusters for high-efficiency electromagnetic absorption

The employment of electromagnetic (EM) absorbers integrating elaborate architecture, enhanced microwave absorption and multifunctional features remains a formidable challenge in practical applications including military stealth and incoming 5G electronic information era. Herein, a novel microwave absorber has been fabricated by in-situ growing carbon nanotubes (CNTs) on the prismatic nickel–cobalt (NiCo) clusters derived from Ni-Co layered double hydroxides (NiCo-LDH) via catalytic carbonization of ethyl acetate. The NiCo/CNTs composites with highly porous texture could provide sufficient open space to balance the impedance and introduce magnetic loss mechanism. Accordingly, the absorbers achieved remarkable EM absorption performance with a minimum reflection loss of –46.2 dB at 1.5 mm and broad bandwidth of 5.8 GHz owing to synergistic magnetic-dielectric effects and distinct structural merits. The NiCo/CNTs absorber manifests superior radar wave attenuation by the radar cross section simulation and density functional theory (DFT) was also performed to elucidate the potential mechanisms of the heterostructure formation and performance enhancement in the NiCo/CNTs composites. This work is expected to provide new insights or inspirations to modulate EM properties by rationally designing heterostructure for the elimination of severe EM pollution.

Facile synthesis of Co-Ni layered double hydroxides nanosheets wrapped on a prism-like metal-organic framework for efficient oxygen evolution reaction

The construction of low-cost oxygen evolution reaction (OER) electrocatalysts with high activity and good durability is a considerable challenge for facilitating the efficient utilization of green energy. Herein, the prism-like materials of institute lavoisier frameworks-88 (MIL-88) was first synthesized by a hydrothermal method. Then, Co-Ni layered double hydroxides (CoNi-LDHs) nanosheets were directly wrapped on the MIL-88 surface by electrodeposition to form core-shell MIL-88@CoNi-LDHs composites. Due to the distinct structure and synergistic effect between the MIL-88 core and CoNi-LDHs shell, it was found that MIL-88@CoNi-LDHs had outstanding OER activity with a small Tafel slope (45.55 mV dec-1), low overpotential (314 mV) at 10 mA cm−2, and superior durability. This study provides a prospective pathway to exploit highly efficient low-cost electrocatalysts for OER.

Fabrication of hierarchical Ni nanowires@ NiCo-layered double hydroxide nanosheets core-shell hybrid arrays for high-performance hybrid supercapacitors.

Layered double hydroxides (LDHs) are electrode materials with high specific capacity due to their structure which has a tunable interlayer spacing, however, the disadvantages of their low conductivity and electrochemically limited sites prevent their application in supercapacitors. In this study, we synthesized a high electrochemical performance electrode material with a core-shell structure based on hierarchical nickel nanowires (core) and NiCo LDHs nanosheets (shell). First, hierarchical nickel nanowires, h-Ni NWs, were prepared by the reduction of Ni2+ ions by hydrazine N2H4. Then with the hydrothermal method, the hierarchical nickel nanowires were coated with NiCo LDHs to improve the electrical conductivity of the latter. The electrochemical results showed that the NiCo LDHs@h-Ni NWs electrode had a specific capacity of 1486 C/g at a current density of 1 A/g in 6 M KOH electrolyte with excellent capacity retention (89.7%) after 10,000 charge-discharge cycles at 20 A/g. Due to the synergistic interaction between nickel nanowires and NiCo LDHs which provides excellent conductivity, durability, efficient mesoporous network, and suitable channels for fast ion/electron transfer. In addition, a hybrid supercapacitor (HSC) was fabricated by combining the NiCo LDHs@h-Ni NWs electrode (battery type) with activated carbon (EDLC). The fabricated device provided a high energy density of 72.22 Wh/kg at 800 W/kg, and a maximum power density of 16 kW/kg, the HSC provided an energy density of 50.44 Wh/kg and outstanding cycling stability (88.1% retention after 10,000 cycles).

Mechanistic insights into efficient peroxymonosulfate activation by NiCo layered double hydroxides

The efficient removal of organic refractory pollutants such as dyes and antibiotics in wastewater is crucial for protecting the environment and human health. In this work, a NiCo-layered double hydroxide (NiCo-LDH) with a uniform microspherical, hierarchical structure and a high surface area was successfully synthesized as an effective peroxymonosulfate (PMS) activator for the degradation of various organic dyes and antibiotics. The influence of various parameters on the catalytic activity of the NiCo-LDH was determined. Radical scavenger studies unveiled the major reactive oxygen species (ROSs) generated in the NiCo-LDH/PSM system to be 1O2, SO4•−, and O2•−. Ex-situ X-ray photoelectron spectroscopy (XPS) analysis uncovered the role of Co sites and oxygen vacancy as active sites and revealed the reversible redox properties of NiCo-LDH based on Co2+/Co3+ cycles. The activation mechanism and Rhodamine B (RhB) degradation pathways were experimentally studied and proposed. The NiCo-LDH is highly versatile, reusable and stable as shown by post-catalysis characterizations. This work shows the excellent catalysis performances and provides insights into the activation mechanism of PMS by NiCo-LDH for organic pollutant remediation.

One-pot synthesis of flower-like Ni-Co/reduced graphene oxide layered double hydroxide nanocomposites as advanced electrodes for high-performance asymmetric supercapacitors

Novel electrode materials with appropriate architectures are always desired to increase the energy density of supercapacitors. Here, the design and fabrication of NiCo-layered double hydroxides (NC-LDH) in composition with reduced graphene oxide (rGO) were prepared as high-performance electrodes for supercapacitors. In particular, a facile and one-pot scheme was designed for the growth of NC/rGO-LDH composites, which exhibited a high specific surface area of 204 m2/g. The compositional features of the composites, i.e., a two-dimensional flower-like layered architecture and conductive rGO, contributed to their highly impressive specific capacitance (1913.5 F/g at 1 A/g) and excellent cyclic performance. Furthermore, an asymmetric supercapacitor was designed using NC/rGO-LDH composites as the positive electrode and activated carbon as the negative electrode, which displayed a high energy density of 59.2 Wh/kg at a power density of 750 W/kg.

Self-supporting electrode for flexible supercapacitors: NiCo-layered double hydroxide derived from metal organic frameworks wrapped on graphene/polyaniline nanotubes@cotton cloth

Nowadays, constructing hetero-structure materials is an efficacious procedure to uplift the electrochemical performance of layered double hydroxide (LDH) materials. The logical design of such elegant nanostructures is still challenging. Herein, NiCo-LDH nanosheets derived from Co-ZIF grown on graphene/polyaniline nanotube (G/PANI-NT)@cotton cloth (CC) was synthesized by a facile and novel two-step strategy for supercapacitors. Such hetero-structures give a 30.63 m2 g−1 surface area and more subjected electrochemical active sites. The supercapacitor performance results exhibit that the NiCo-LDH/G/PANI-NT@CC electrode has the best supercapacitor performance when it is used as a pseudocapacitor. By the ratio of Ni/Co = 2:1 in the precursor solution, the electrode shows an areal specific capacitance of 88.15 mF cm−2 at a current density of 0.075 mA cm−2. The electrochemical performance of the electrodes was perused using a redox-additive electrolyte. The electrochemical performance of the NiCo-LDH/G/PANI-NT@CC electrode was amended using K2S2O8 in a 3 M KOH solution. Considerably, the areal specific capacitance of NiCo-LDH/G/PANI-NT@CC (181.17 mF cm−2) increased to 431.30 mF cm−2, by changing the K2S2O8 concentration in KOH solution at a current density of 0.075 mA cm−2. Long-term stability test demonstrates that 84.05 % of the original capacitance remains after 10,000 cycles at the current density of 0.2 mA cm−2. The results indicate that NiCo-LDH/G/PANI-NT@CC will be an appropriate candidate for high-performance supercapacitors. The NiCo-LDH/G/PANI-NT@CC//NiCo-LDH/G/PANI-NT@CC flexible solid-state supercapacitor was assembled with the PVA/KOH gel electrolyte.

Construction of Ni‐Co‐Fe Hydr(oxy)oxide@Ni‐Co Layered Double Hydroxide Yolk‐Shelled Microrods for Enhanced Oxygen Evolution

The exploration of earth-abundant and efficient electrocatalysts toward the oxygen evolution reaction (OER) is critical for sustainable energy storage and conversion devices. In this work, we report a self-engaged strategy to fabricate a yolk-shelled OER electrocatalyst. Starting with a metal-organic framework, Co-Fe layered double hydroxide (LDH)@zeolitic imidazolate framework-67 (ZIF-67) yolk-shelled structures are formed in one step. Afterwards, these ZIF-67 building blocks are transformed into Ni-Co LDH nanocages to form the Ni-Co-Fe hydr(oxy)oxide@Ni-Co LDH yolk-shelled microrods (NiCoFe-HO@NiCo-LDH YSMRs) through an ion-exchange reaction. Owing to the structural and compositional merits, the NiCoFe-HO@NiCo-LDH YSMR electrocatalyst exhibits an overpotential of 278 mV to reach the current density of 10 mA cm-2 , a small Tafel slope of 49.7 mV dec-1 , and good stability in alkaline media.

Surface active oxygen engineering of photoanodes to boost photoelectrochemical water and alcohol oxidation coupled with hydrogen production

Photoelectrochemical conversion of solar energy into fuels (or chemicals) is in urgent need of efficient photoanodes to drive its practical applications. Nevertheless, the development of high performance photoanode usually suffers from slow charge transfer and sluggish surface catalytic kinetics. Here, we report a surface active oxygen engineering strategy through the modification and activation of NiCo layered double hydroxide (NiCo-LDH), where the activated NiCo-LDH (NiCo-LDH-Act) captures the photogenerated holes and acts as cocatalyst for surface oxidation reactions. The as-developed BiVO4/NiCo-LDH-Act achieves more than 3-fold higher photocurrent density than that of pristine BiVO4. Experimental integrated with theoretical studies further testify the bifunctional of NiCo-LDH-Act for hole transport and catalytic reactions. Moreover, the adsorbed ·OH originated from active oxygen enables efficient oxidation of glycerol to attain 1,3-dihydroxyacetone (DHA) with a productivity of 20.5 μmol cm–2 h–1 at 1.4 V vs. RHE with simultaneously producing hydrogen at the cathode.

In Situ Growth of NiCo Layered Double Hydroxide on Biomass Waste‐Based Substrate: A Novel Material with 3D Interconnected Structure as Electrodes for Supercapacitors

Next‐generation energy storage systems require green and renewable electrodes with a high specific capacity, which combine biomass waste and bimetallic hydroxide synergically to satisfy environmental enhancements and economic benefits. Herein, a novel approach to improving the electrical conductivity of bimetallic materials by in situ growing NiCo layered double hydroxides (LDHs) with pseudocapacitance capability on KMnO4‐activated fungus bran‐derived carbons (FBCs) is reported, achieving improved electrochemical performance in supercapacitors (SCs). The hierarchical porous FBC substrate contributes to the homogeneous growth of the LDHs and high electronic and ionic conductivity. The optimal composite (FBC/NCL‐3) with a 3D interconnected structure provides a specific capacitance of 1938 F g−1 at a current density of 1 A g−1. Correspondingly, the hybrid battery‐SC device composed of FBC/NCL‐3 and FBC provides favorable stability (76% specific capacity retention at 5 A g−1 for 3000 cycles) with an operating voltage of 1.4 V and a high energy density of 37.3 Wh kg−1 at a power density of 695.6 W kg−1. This work demonstrates a promising strategy using FBC as a substrate for growing LDH materials aiming to achieve high‐performance SCs.

High-Performance Ternary NiCoMo Electrocatalyst with Three-Dimensional Nanosheets Array Structure.

Oxygen evolution reaction is a key process in hydrogen production from water splitting. The development of non-noble metal electrode materials with high efficiency and low cost has become the key factor for large-scale hydrogen production. Binary NiCo-layered double hydroxide (LDH) has been used as a non-noble metal electrocatalyst for OER, but its overpotential is still large. The microstructure of the catalyst is tuned by doping Mo ions into the NiCo-LDH/NF nanowires to form ternary NiCoMo-LDH/NF nanosheet catalysts for the purpose of enhancing the active sites and reducing the initial overpotential. Only 1.5 V (vs. reversible hydrogen electrode (RHE), ≈270 mV overpotential) is required to achieve a catalytic current density of 10 mA cm-2 and a small Tafel slope of 81.46 mV dec-1 in 1 M KOH solution, which manifests the best performance of NiCo-based catalysts reported up to now. Electrochemical analysis and micro-morphology show that the high catalytic activity of NiCoMo-LDH/NF is attributable to the change of the microstructure. The interconnected nanosheet arrays have the obvious advantages of electrolyte diffusion and ion migration. Thus, the active sites of catalysts are significantly increased, which facilitates the adsorption and desorption of intermediates. We conclude that NiCoMo-LDH/NF is a promising electrode material for its low cost and excellent electrocatalytic properties.

Construction of 0D/1D/2D MXene nanoribbons-NiCo@NC hierarchical network and their coupling effect on electromagnetic wave absorption

The construction of MXene-based composites with rational hierarchical structures and networks has emerged as a promising candidate for high-performance electromagnetic wave (EMW) absorption, stemming from the unpredictable formation of multiple components and multiple interfaces. Herein, a stable and porous 0D/1D/2D MXene nanoribbons (NRs)-NiCo@NC hierarchical network consisting of 0D NiCo alloy embedded in nitrogen (N)-doped carbon (NiCo@NC), 1D Ti3C2Tx MXene nanoribbons, and 2D N-doped carbon nanosheets is rationally constructed for EMW absorption. The “shearing effect” of alkaline KOH can induce the formation of 1D MXene nanoribbons with staggered-connected nanoribbon network and macroporosity, which greatly increases the attenuation of multiple reflections of EMW. Meanwhile, MXene nanoribbons can serve as a structural network for the subsequent growth of 2D NiCo layered double hydroxide (LDH) ultrathin nanosheets as well as a conductive network for conduction loss. The 0D NiCo@NC derived from NiCo LDH nanosheets inherit excellent eddy current losses that contribute to magnetic loss and abundant N heteroatoms that contribute to dipole polarization. Furthermore, thanks to the coupling effect, 0D/1D/2D hierarchical network provides numerous interfaces that contribute to interfacial polarization and considerable exchange resonances that contribute to magnetic loss. As a result, 0D/1D/2D MXene nanoribbons-NiCo@NC hierarchical network exhibits robust EMW absorption performance with a reflection loss (RL) value of −57.1 dB at a thickness of 4.82 mm and a RL value of −33.19 dB at a thickness of only 1.4 mm. This study provides new inspiration for the future construction of EMW absorbers with hierarchical networks.

Highly sensitive surface plasmon resonance sensor for detection of Methylene Blue and Methylene Orange dyes using NiCo-Layered Double Hydroxide

Surface plasmon resonance (SPR) sensor is a versatile technique to detect toxic materials in the environment. In this study, the SPR technique was used to detect the environmental contaminant dyes such as methylene blue (MB) and methylene orange (MO). The surface of the gold layer was modified using NiCo-layered double hydroxide (LDH) which was fabricated with the electrodeposition method and characterized using field emission scanning electron microscopy, X-ray diffraction spectroscopy, and transmission electron microscopy. The thickness of LDH was controlled by deposition time and a homogeneous coating of LDH was obtained in the short time range of less than 150s. The adsorption of MB and MO on LDH was studied using the SPR technique based on angular modulation. Langmuir adsorption isotherm was fitted for data of adsorbents and the adsorption mechanism was described. The sensor limit and the response time were about 0.005 ppm and 268 s, respectively. It was proved that the sensitivity of the sensor can be controlled by the thickness of the LDH layer. Results indicated that the glass/Au/ NiCo-LDH system is fast and efficient for the detection of the MB and MO dyes in a short time.

Electrochemical Sensor Based on Ni-Co Layered Double Hydroxide Hollow Nanostructures for Ultrasensitive Detection of Sumatriptan and Naproxen.

In this work, Ni-Co layered double hydroxide (Ni–Co LDH) hollow nanostructures were synthesized and characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and Fourier-transform infrared spectroscopy (FT-IR) techniques. A screen-printed electrode (SPE) surface was modified with as-fabricated Ni–Co LDHs to achieve a new sensing platform for determination of sumatriptan. The electrochemical behavior of the Ni–Co LDH-modified SPE (Ni-CO LDH/SPE) for sumatriptan determination was investigated using voltammetric methods. Compared with bare SPE, the presence of Ni-Co LDH was effective in the enhancement of electron transport rate between the electrode and analyte, as well as in the significant reduction of the overpotential of sumatriptan oxidation. Differential pulse voltammetry (DPV) was applied to perform a quantitative analysis of sumatriptan. The linearity range was found to be between 0.01 and 435.0 μM. The limits of detection (LOD) and sensitivity were 0.002 ± 0.0001 μM and 0.1017 ± 0.0001 μA/μM, respectively. In addition, the performance of the Ni-CO LDH/SPE for the determination of sumatriptan in the presence of naproxen was studied. Simultaneous analysis of sumatriptan with naproxen showed well-separated peaks leading to a quick and selective analysis of sumatriptan. Furthermore, the practical applicability of the prepared Ni-CO LDH/SPE sensor was examined in pharmaceutical and biological samples with satisfactory recovery results.

Insights into the charge transfer kinetics in BiVO4 photoanodes modified with transition metal-based oxygen evolution electrocatalysts

BiVO4 is a promising photoanode for photoelectrochemical (PEC) water splitting. Nevertheless, the sluggish water oxidation on its surface causes severe charge carriers recombination and thus reduces the overall efficiency. To overcome these imperfections, BiVO4 photoanodes were prepared and modified with transition metal-based oxygen evolution electrocatalysts, namely, NiFe, CoNi, and CoFe–layered double hydroxides (LDHs) oxygen evolution catalysts (OECs). The kinetics of charge transfer and recombination in the prepared photoanodes were studied by transient photocurrent and intensity-modulated photocurrent spectroscopy (IMPS). The rate constants of charge transfer and recombination were determined and correlated with the generated photocurrent to disclose the function of each electrocatalyst. It was concluded that the three investigated LDHs exhibit a comparable electrocatalytic activity at low applied potential, but CoNi–LDH has a superior passivation effect. Contrary to CoFe and NiFe–LDHs, CoNi–LDH passivates the surface states and unpins the Fermi level as proved by IMPS and photovoltage measurements. This study provides a systematic pathway to disclose the role of LDH OECs on BiVO4 surface which is an essential step for the rational design of efficient photoanodes.

MXene-MnO2-CoNi layered double hydroxides//activated carbon flexible asymmetric supercapacitor

Rational design of the structure and effective utilization of the active sites of electrode materials can improve the electrochemical performances of supercapacitors. Herein, MnO2 and CoNi layered double hydroxides (CoNi-LDHs) are sequentially deposited on carbon cloth/MXene (CC/MXene) electrode by electrodeposition to prepare CC/MXene-MnO2-CoNi-LDHs (CC/MMCoNi) electrode. The nanoarray structure can provide a large specific surface area and more channels, which facilitate rapidly ion transfer and electron migration between electrolyte and electrode. The impacts of the presence or absence of MXene and different Co and Ni ratios on the electrochemical performances are investigated in detail. It is found that the presentation of MXene on the one hand enhances the conductivity of the electrode, on the other hand supplies more active sites for the attachment of MnO2. In the situation of Co:Ni = 1:2, CoNi-LDHs having the largest nanosheets provides the high capacitance of 922 F g−1 (553 C g−1) at 1 A g−1. Asymmetric supercapacitor is successfully fabricated by assembling CC/MMCoNi positive electrode with activated carbon (AC) negative electrode. The device can provide 1.7 V voltage window and an energy density of 65 W h kg−1 at a power density of 1491 W kg−1. The device has excellent practical application ability and can effectively resist external forces, which provide theoretical basis and technical support for the subsequent development of a new generation of flexible supercapacitors.

Oxygen Vacancies Boosted by Laser Irradiation Enable NiCo Layered Double Hydroxide with a High Oxygen Reduction/Evolution Catalytic Activity in Zn–Air Batteries and Water Splitting

Oxygen Vacancies Boosted by Laser Irradiation Enable NiCo Layered Double Hydroxide with a High Oxygen Reduction/Evolution Catalytic Activity in Zn–Air Batteries and Water Splitting

Fibril-Type Textile Electrodes Enabling Extremely High Areal Capacity through Pseudocapacitive Electroplating onto Chalcogenide Nanoparticle-Encapsulated Fibrils.

Effective incorporation of conductive and energy storage materials into 3D porous textiles plays a pivotal role in developing and designing high-performance energy storage devices. Here, a fibril-type textile pseudocapacitor electrode with outstanding capacity, good rate capability, and excellent mechanical stability through controlled interfacial interaction-induced electroplating is reported. First, tetraoctylammonium bromide-stabilizedcopper sulfidenanoparticles (TOABr-CuS NPs) are uniformly assembled onto cotton textiles. This approach converts insulating textiles to conductive textiles preserving their intrinsically porous structure with an extremely large surface area. For the preparation of textile current collector with bulk metal-like electrical conductivity, Ni is additionally electroplated onto the CuS NP-assembled textiles (i.e., Ni-EPT). Furthermore, a pseudocapacitive NiCo-layered double hydroxide (LDH) layer is subsequently electroplated onto Ni-EPT for the cathode. The formed NiCo-LDH electroplated textiles (i.e., NiCo-EPT) exhibit a high areal capacitance of 12.2 F cm-2 (at 10mA cm-2 ), good rate performance, and excellent cycling stability. Particularly, the areal capacity of NiCo-EPT can be further increased through their subsequent stacking. The 3-stack NiCo-EPT delivers an unprecedentedly high areal capacitance of 28.8 F cm-2 (at 30mA cm-2 ), which outperforms those of textile-based pseudocapacitor electrodes reported to date.

Metal boride-decorated CoNi layered double hydroxides supported on muti-walled carbon nanotubes as efficient hydrolysis catalysts for sodium borohydride

Without effective and secure hydrogen production, it is impossible to utilize hydrogen energy on a large scale. Whereas hydrogen emission from NaBH4 hydrolysis with high hydrogen yield is an impressively efficient hydrogen supply method. However, it is affected by sluggish hydrogen production kinetics and low yields, therefore it is required to develop hydrolysis catalysts with good performance under alkaline conditions. In this study, a composite of unique CoNi layered double hydroxide (CoNi-LDH) nanosheets interconnected by muti-walled carbon nanotubes (MWCNTs) was prepared for the first time, and the surface was modified with metal borides produced by in-situ reduction. Among them, CoNi-LDH nanosheets are created when CoNi-MOF spontaneously derivates in alkaline electrolytes. The successful preparation of CoB-LDH-CNT has been confirmed by SEM, TEM, EDS, XRD, and XPS characterization. The hydrolysis experiments show that it has good catalytic activity with an optimal hydrogen generation rate (HGR) of 5167.72 mL·min−1·g−1 and low activation energy (Ea) of 29.93 kJ·mol−1. After ten cycles of experiments, it still has 75.4% of the initial performance, showing excellent stability, which may be attributed to the fact that MWCNTs can help to reconnect broken nanosheets during the reaction. This interconnected multistage structure offers a new methodology for enhancing the catalytic performance of metal boride and metal hydroxide materials.