Porous Nickel Oxide Research Articles

Thermally-driven electrokinetic power generation system utilizing microporous NiO wicks and nanoporous AAO membranes for low-grade heat harvesting

Low-grade heat (T<100 ℃) exists ubiquitously in the environment, but it is difficult to harvest and utilize due to existing technology’s limitations. It would be significant to harvest this kind of energy through effective acquisition techniques. Here, we propose a micro/nano porous membranes low-grade heat harvesting system based on the thermoelectric effect, which uses the temperature gradient to induce the separation and transmission of electrolyte solution ions in the porous membrane to convert low-grade thermal energy into electrical energy. Two power generation materials of microporous nickel oxide (NiO) wicks and nanoporous anodic aluminum oxide (AAO) membranes were investigated experimentally. In the porous NiO wick experiment, it is observed that the wick significantly improves the thermoelectric conversion performance. In particular, when the temperature difference is 50 ℃, the open circuit voltage of the system reaches 215 mV, which is about 300 % higher than the case without the porous NiO wick. In addition, in the AAO porous membranes experiment, we found that at the low concentration, by collecting ambient heat with a temperature difference of 5 ℃, the system obtained the output power of about 6 nW, which improved the 2 ∼ 3 orders of magnitude compared with the previous research reports. This work offers a promising method for developing high-performance and low-cost low-grade heat harvesting systems.

Electrochemical and impedance analysis of nickel oxide nanoflakes-based electrodes for efficient chromo supercapacitors

In response to the dynamic advancement of our growing world, there is a tenacious need for sophisticated technologies and continuous refinement of existing knowledge through rigorous scientific endeavors, all with a focus on achieving sustainable development goals for a cleaner and more prosperous future. In this context, this study involves a novel approach to the synthesis of highly porous and stable nickel oxide (NiO) nanoflakes assembled with stacked nanosheet thin films through hydrothermal methods. These films are in-detail examined for their redox-active chromo-supercapacitive properties. The hydrothermal synthesis technique yields thin films with exceptional adhesion to the electrode surface, remarkable chemical stability, and suitable porous structure. These characteristics are strategically employed to facilitate rapid ion intercalation and deintercalation processes, thereby enhancing electrochemical activity. Notably, films deposited for 6-hour reaction times deliver a higher areal capacitance of 140 mF/cm² (and capacity of 70 mC/cm2) at 0.5 mA/cm², which is higher than other electrodes and earlier reports. In-situ, optical investigations further underscore the high coloration efficiency of 44.14 cm²/C, coupled with large optical modulation of 56.5 % and enduring the electrochemical and electrochromic stability. Further research and optimization of NiO-based materials hold significant potential for the development of efficient, smart, and sustainable energy storage solutions in the evolving field of electrochromic supercapacitors to meet the demands of next-generation electronic systems.

Ultralong lifespan and high energy density soft-pack asymmetric supercapacitors based on electrochemically activated porous nickel oxide nanosheet array

Nickel oxide (NiO) with high theoretical capacity is considered a promising energy storage material, however, its actual capacitance and stability are unsatisfactory. In this work, a facile electrochemical activation is proposed to significantly improve the electrochemical performance of porous NiO nanosheet arrays on carbon cloth (CC) in-situ prepared by facile hydrothermal method and subsequent high-temperature calcination. Experimental characterization and density functional theory calculations have shown that this electrochemical activation process can introduce more oxygen vacancies and defects, reduce the crystallinity and nickel valence state of NiO, increase the structural looseness of the nanosheet array and electrical conductivity as well as adsorption energy for hydroxide. By utilizing these structural regulations, the specific capacitance of electrochemically activated NiO/CC is significantly enhanced from 308 to 914 F g−1. The soft-pack asymmetric supercapacitor offers a high energy density of 38.5 Wh kg−1 and exhibit an ultralong lifespan of up to 20,000 cycles with 96.2% capacitance retention. Such a soft-pack asymmetric supercapacitor illuminates different electronic devices, demonstrating enormous potential in practical applications.

Air-stable and reusable porous silica-supported ultrafine Nix-NiO nanoparticles for semi-hydrogenation of alkynes

The practical application of non-noble metal-based hydrogenation catalysts is limited because of their low activity and easy oxidation in air. Here, porous silica-supported ultrafine nickel oxide (NiO) was prepared by calcining an organic–inorganic hybrid 3D nanomaterial that was formed via the Michael addition/Schiff’s base reaction, and hydrolyzation of triethoxysilane. NiO nanoparticles with ca. 2.6 nm diameter was uniformly dispersed and confined in the cogenerated mesoporous SiO2 skeleton, thanks to the coordination between pyrogallol/amino units and Ni2+ ions, and the isolation effect of Si-O-Si network. The as-prepared catalyst featured mesoporous structure and high specific surface area (715 m2/g), and exhibited excellent activity, selectivity and reusability in the semi-hydrogenation of alkynes. Small amount of metallic nickel (Nix-NiO) that formed on the surface of NiO nanoparticles during the semi-hydrogenation acted as the active species, and the moderate adsorption/desorption energies on Nix-NiO facilitated the activity enhancement. Most importantly, it showed constant catalytic activity and selectivity after a long-term storage in air. This work provides a green and feasible strategy, as an alternative to the traditional impregnation method, for the preparation of ultrafine metal-supported catalysts with air-stability and reusability.

Development of Nanoporous Nickel Oxide Materials as Electrodes for Supercapacitors

As a potential electrochemical energy storage device, supercapacitor has been researched owing to its low weight, excellent power density, outstanding charging rate, and long durability. For the supercapacitor, the electrode material and its morphology determine its overall performance. Nickel oxide (NiO) is a promising material for the electrode because of its low cost, high specific capacitance, and eco-friendly manufacturing process. In this research, we developed a simple and cost-effective method to fabricate supercapacitor electrodes by electrospinning and thermal annealing, making porous nickel oxide nanofibers directly grow on 3D-nickel foam. The binder-free design and porous structure of electrodes enhance the ion transport and electron transfer in the supercapacitor. The crystal structure of NiO was identified by X-ray diffractometry (XRD). The morphological and microstructural characterization was analyzed by scanning electron microscopy (SEM). The electrochemical test was carried out in a three-electrode electrochemical cell with the obtained foamed NiO as the working electrode, the platinum sheet as the counter electrode, and the Ag/Cl electrode as the reference electrode. The electrochemical performance was evaluated by using cyclic voltammetry (CV), galvanostatic charge/discharge technique, and electrochemical impedance spectroscopy (EIS). Due to the large specific surface area and good electrical conductivity of the NiO electrode, the supercapacitor exhibited excellent electrochemical performance (591 F/g at 2 A/g). After 1500 cycles of charging and discharging at 10 A/g, the capacitance of the supercapacitor using the NiO electrode increased by 21.7% with excellent cycle stability.

Highly porous NiO microstructure for NO2 detection

Nickel oxide (NiO) thin films were deposited on to the glass substrates via chemical bath deposition (CBD) method at various deposition times of 5, 6, 7 and 8 h. The X-ray diffraction (XRD) study showed the cubic crystal structure of NiO. The field emission scanning electron microscopy (FE-SEM) images exhibit the porous structured morphology composed of randomly oriented nanosheets. The atomic force microscopy (AFM) analysis reveals the maximum surface roughness of 107.9 nm for NiO film deposited at 7 h. The X-ray photoelectron spectroscopy (XPS) study reveals the presence of Ni2+ and Ni3+ chemical states. The transmission electron microscopy (TEM) images reveal an average size of 5 nm for NiO nanocrystalline particles. The nitrogen dioxide (NO2) gas sensing performance was tested at various working temperatures and gas concentrations. The sensing tests showed 45.6 % response to 100 ppm NO2 at 200 °C with Tresponse = 13 s and Trecovery = 146 s.

Solution Combustion Synthesis of Ni-Based Nanocatalyst Using Ethylenediaminetetraacetic Acid and Nickel-Carbon Nanotube Growth Behavior.

We studied the influence of the ethylenediaminetetraacetic acid (EDTA) content used as combustion fuel when fabricating nickel oxide (NiO) nanocatalysts via solution combustion synthesis, as well as the growth behavior of carbon nanotubes (CNTs) using this catalyst. Nickel nitrate hexahydrate (Ni(NO3)2∙6H2O) was used as the metal precursor (an oxidizer), and the catalysts were synthesized by adjusting the molar ratio of fuel (EDTA) to oxidizer in the range of 1:0.25 to 2.0. The results of the crystal structure analysis showed that as the EDTA content increased beyond the chemical stoichiometric balance with Ni(NO3)2∙6H2O (F/O = 0.25), the proportion of Ni metal within the catalyst particles decreased, and only single-phase NiO was observed. Among the synthesized catalysts, the smallest crystallite size was observed with a 1:1 ratio of Ni ions to EDTA. However, an increase in the amount of EDTA resulted in excessive fuel supply, leading to an increase in crystallite size. Microstructure analysis revealed porous NiO agglomerates due to the use of EDTA, and differences in particle growth based on the fuel ratio were observed. We analyzed the growth behavior of CNTs grown using NiO nanocatalysts through catalytic chemical vapor deposition (CCVD). As the F/O ratio increased, it was observed that the catalyst particles grew excessively beyond hundreds of nanometers, preventing further CNT growth and leading to a rapid termination of CNT growth. Raman spectroscopy was used to analyze the structural characteristics of CNTs, and it was found that the ID/IG ratio indicated the highest CNT crystallinity near an F/O ratio of 1:1.

Long-term stability electrochromic electrodes based on porous tungsten trioxide and nickel oxide films via a facile triple pulse electrodeposition

Herein, a facile triple pulse electrodeposition was used to fabricate porous films such as tungsten trioxide (WO3) and nickel oxide (NiO) on indium tin oxide (ITO) substrates. These porous films outperformed corresponding compact films formed by continuous electrodeposition in terms of long-term stability. The maximum transmittance modulation of P-WO3 and P–NiO films were 57.0% and 52.1%, respectively, and changed insignificantly after 10,000 cycles, whereas C-WO3 and C–NiO films were degraded after 2500 and 1000 cycles, respectively. Not only does the porous morphology increases the electrochemical active surface area, but it also provides an efficient pathway for ion diffusion and charge transfer, resulting in fast kinetics, low resistance, high electro-activity, and excellent ion reversibility. This work will hopefully inspire more researchers to improve electrodeposition film fabrication and promote electrochromic device industrialization.

Surfactant regulated Core-Double-Shell NF@NiO nanosheets matrix as integrated anodes for Lithium-Ion batteries

The direct oxidation of three-dimensional nickel foam (3D NF) to nickel oxide (NiO) as integrated anode material for lithium-ion batteries (LIBs) has attracted significant attention towards achieving high-areal-capacity and high-energy density LIBs. However, the rate capability of such monolithic NiO in LIBs usually falls off rapidly due to the poor electrical conductivity that hindered its ionic transport kinetics. Herein, to ease the ionic transport constrains, a surfactant-regulated strategy is developed for preparing in-situ core-double-shell architecture that consists of core nickel skeleton, dense nickel oxide shell and porous nickel oxide nanosheets (NS) shell as anode materials for LIBs. Among the three employed surfactants including cationic surfactant, anionic surfactant and nonionic surfactant, the anionic surfactant (sodium dodecyl sulfate, SDS) modulated anode denoted SDS-NF@NiONS exhibits ultrahigh reversible areal capacity of 8.64 mAh cm−2@ 0.4 mA cm−2, and excellent rate areal capacity of 5.20 mAh cm−2 @ 3.0 mA cm−2, which did not only show the best ever reported NiO-based high-areal-capacity based electrodes, but also demonstrate impressive performance in practical full cell LIBs. In addition, in-situ Raman and kinetic analyses confirm the mechanism of Li-ion storage and facile ionic transport kinetics in this proposed design.

Novel self-assembled porous yolk-shell NiO nanospheres with excellent electrochromic performance for smart windows

With the rapid development of optoelectronics, electrochromic (EC) materials (ECMs) with the advantages of low power consumption, easy viewing, high contrast ratio, etc. have attached more and more attention from the fields of smart windows, electronic billboards, emerging wearable and portable electronics, and other next-generation displays. Nickel oxide (NiO) is a promising candidate for high-performance ECMs because of its neutral-colored states and low cost. However, NiO-based ECMs still face the problem of slow switching speed due to their low electrical conductivity and small lattice spacing. Metal-organic frameworks (MOFs) are promising candidates to fabricate hollow and porous transition metal oxides (TMOs) with high ion transport efficiency, excellent specific capacitance, and electrochemical activities. In this work, porous yolk-shell NiO nanospheres (PYS–NiO NSs) were synthesized via a solvothermal and subsequent calcination process of Ni-MOF, which exhibited outstanding EC performance. Because the large specific surface areas and hollow porous nanostructures were conducive to ionic transport, PYS-NiO NSs exhibited a fast coloring/bleaching speed (3.6/3.9 s per one coloring/bleaching cycle) and excellent cycling stability (82% of capacity retention after 3000 cycles). These superior EC properties indicated that the PYS-NiO NSs was a promising candidate for high-performance EC devices. This work provides a new and feasible strategy for the efficient preparation of TMOs ECMs with good EC performance, especially fast switching speed.

A facile electrochemical lithiation method to prepare porous nickel oxide electrodes with high electrochromic performance

A facile electrochemical lithiation method was developed in the framework of the wet chemical route, and NiO films with various lithium contents have been successfully prepared. The structure and electrochromic properties were characterized using SEM, HRTEM, XRD, XPS, etc. The results indicate that all NiO films show a porous morphology, and the ratio of Ni3+/Ni2+ increases from 1.12 to 1.46 after electrochemical lithiation. The storage capacity in lithium electrolytes, effective ionic diffusion rate, transmittance modulation, and coloring efficiency are effectively improved. The optimized NiO electrode exhibits an excellent storage capacity of 6.4 mC/cm2 and transmittance modulation at 550 nm of 35.7%, compared to the pristine NiO (Q = 4.4 mC/cm2, ΔT = 24.3%). Two electrochromic devices were respectively assembled with the pristine and lithiated NiO electrodes as the anodic electrochromic layer. The latter exhibits higher transmittance modulation and coloring efficiency, proving that the electrochemical lithiation method is an effective way to prepare high-performance electrochromic devices.

Hierarchical porous NiO doped ZnO nanocomposite for formaldehyde gas sensor with high sensitivity, fast response/recovery and good selectivity

Formaldehyde (HCHO) is a kind of indoor pollution gas which seriously harms human health. High properties gas sensor for formaldehyde are essential for indoor air quality monitoring. The development of new nanostructured composites as gas sensing materials is seen as a viable way to improve sensing performance. In this study, a new type of layered porous nickel oxide doped zinc oxide nanocomposite with sunflower straw as a template (SFS NiO/ZnO) was synthesised. The structure and morphology of the material was characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These results exhibit that the synthetic SFS NiO/ZnO successfully maintains the original pore morphology of the sunflower straw material and the framework consists of a large number of nanoparticles of uniform size and shape. The gas sensing performance of the prepared samples was tested and the results showed that the SFS NiO/ZnO biocomposite had promising sensing performance for formaldehyde. The response of the SFS NiO/ZnO gas sensor working at 240 °C was 42 for 100 ppm formaldehyde with response and recovery times of 9 s and 8 s, respectively. The lower limit of detection is 148 ppb. Compared with SFS ZnO, the significant improvement of formaldehyde sensing properties could be attributed to its increased oxygen vacancy concentration and the presence of p-n type heterojunctions.

Ni2P Nanoparticle-Inserted Porous Layered NiO Hetero-Structured Nanosheets as a Durable Catalyst for the Electro-Oxidation of Urea.

The electro-oxidation of urea (EOU) is a remarkable but challenging sustainable technology, which largely needs a reduced electro-chemical potential, that demonstrates the ability to remove a notable harmful material from wastewater and/or transform the excretory product of humans into treasure. In this work, an Ni2P-nanoparticle-integrated porous nickel oxide (NiO) hetero-structured nanosheet (Ni2P@NiO/NiF) catalyst was synthesized through in situ acid etching and a gas-phase phosphating process. The as-synthesized Ni2P@NiO/NiF catalyst sample was then used to enhance the electro-oxidation reaction of urea with a higher urea oxidation response (50 mA cm−2 at 1.31 V vs. RHE) and low onset oxidation potential (1.31 V). The enhanced activity of the Ni2P@NiO/NiF catalyst was mainly attributed to effective electron transport after Ni2P nanoparticle insertion through a substantial improvement in active sites due to a larger electrochemical surface area, and a faster diffusion of ions occurred via the interactive sites at the interface of Ni2P and NiO; thus, the structural reliability was retained, which was further evidenced by the low charge transfer resistance. Further, the Ni2P nanoparticle insertion process into the NiO hetero-structured nanosheets effectively enabled a synergetic effect when compared to the counter of the Ni2P/NiF and NiO/NiF catalysts. Finally, we demonstrate that the as-synthesized Ni2P@NiO/NiF catalyst could be a promising electrode for the EOU in urea-rich wastewater and human urine samples for environmental safety management. Overall, the Ni2P@NiO/NiF catalyst electrode combines the advantages of the Ni2P catalyst, NiO nanosheet network, and NiF current collector for enhanced EOU performance, which is highly valuable in catalyst development for environmental safety applications.

Influence of fuel to oxidizer ratio on the supercapacitive properties of NiO synthesized by solution combustion method

Porous Nickel oxide nanocrystallites were successfully synthesized by a facile single-step glycine assisted solution combustion method without a post calcination treatment. Effect of fuel to oxidizer (F/O) ratio on the combustion behaviour, crystallite size, surface characteristics, morphology, and agglomeration were thoroughly investigated. A systematic variation of crystallite size with F/O ratio was revealed from PXRD studies. BET studies showed a decrease of surface area with increase of F/O ratio. Highly porous morphology of NiO nanocrystallites synthesized at low F/O ratio (0.5) was evident from scanning electron micrograph (SEM). Transmission electron microscopy (TEM) studies showed polycrystalline nature of the material. NiO nanocrystallites exhibit high thermal stability, which was revealed from thermal analysis. The maximum specific capacitance obtained for NiO synthesized at different F/O ratios ranged from 215.6 to 99.2 C/g at 5 mV/s scan rate and 174.7 to 73.0 C/g at 10 A/g current density. Highest value of specific capacitance and lowest values of equivalent series resistance and charge transfer resistance were exhibited by NiO synthesized at low F/O ratio of 0.5. The enhanced electrochemical performance of the sample synthesized at low F/O ratio was benefited mainly from its high surface area and optimal pore size for the diffusion of ions and electrons within the electrode. An asymmetric device fabricated using NiO as the positive electrode and activated carbon derived from phyllanthus emblica as the negative electrode and 3 M KOH as the electrolyte delivered an energy density of 12 Wh/kg at a power density of 427 W/kg.

Simple Controllable Fabrication of Novel Flower‐Like Hierarchical Porous NiO: Formation Mechanism, Shape Evolution and Their Application into Asymmetric Supercapacitors

AbstractThe rational tailoring of micro‐ and mesoporous distribution for porous transition metal oxide‐based nanomaterials is an important factor to control their electrochemistry performances. Herein, flower‐like hierarchical microspheres assembled by ultrathin nickel oxide (NiO) nanosheets were synthesized by a facile solvothermal route and subsequent annealing process. Theoretical analysis and experimental results demonstrate that NiO ultrathin nanosheets prepared by calcination at 450 °C (N‐450) have the optimal micro‐ and mesoporous distribution. The optimal microstructure provides plenty of ion transport channels and abundant active sites. As expected, the N‐450 electrode delivers an ultrahigh specific capacity of 546.53 F g−1at a current density of 2 A g−1, which is greater than other electrodes. Remarkably, the assembled N‐450//AC asymmetric supercapacitor (ASC) achieves a high energy density of 29.7 Wh kg−1(at a power density of 800 W kg−1) and exhibits an excellent cycling stability. This work demonstrates an available avenue to enhance the performance of supercapacitor by accurately controlling calcination temperature to adjust the porous architectures of ultrathin NiO nanosheets.

Study on Ion Transport Mechanism of Zinc-Nickel Single-Flow Battery with Different Porous Electrode Structures based on Lattice Boltzmann Method

Since the microstructure of porous electrode is very important to the performance of zinc-nickel single-flow battery, this paper reconstructed the microstructure of porous nickel oxide electrode by quartet structure generation set (QSGS) method. The flow mass transfer and electrochemical reaction in porous electrode were simulated by lattice Boltzmann method (LBM). The effects of different porous electrode structures (porosity, particle size and electrode thickness) on local ion concentration distribution and charging performance are studied from the perspective of seepage and mass transfer in pores. It is found that the ion concentration in the electrode presents an uneven distribution due to the randomness of the particle size and distribution of active substances. The uneven distribution of OH − concentration caused the difference of charging depth in the direction of electrode thickness, and the uneven distribution of H + concentration caused the difference of charging depth in the radial direction of particles. Under different pore structures, the decrease of porosity and particle size can increase the diffusion rates of OH − and H +, and then promote the electrochemical reaction rate, improve the charging speed of the battery, and improve the performance of the battery. The larger electrode thickness will increase the OH − diffusion resistance in the electrode, which is not conducive to the diffusion of OH − and reduce the electrochemical reaction rate, thus affecting the diffusion of H +, increasing the concentration polarization and affecting the charging efficiency of the battery. The uneven distribution of OH − concentration caused the difference of charging depth in the direction of electrode thickness, while the uneven distribution of H + concentration caused the difference of charging depth in the radial direction of particles. Under different pore structures, the decrease of porosity and particle size can increase the diffusion rate of OH − and solid phase H +, and then promote the electrochemical reaction rate and accelerate the charging speed. The larger electrode thickness increases the OH − diffusion resistance in the electrode, which is not conducive to OH − diffusion, and then affects H + diffusion and increases concentration polarization.

Improving electrochromic performance of porous nickel oxide electrode via Cu doping

Porous Cu-doped NiO films were fabricated by a cost-effective chemical bath deposition method. The structural characterizations show that Cu doping significantly increase the porosity of the electrodes and the ratio of Ni3+/Ni2+, which are conducive to the electrolyte penetration and chemical reactivity. But the electrochromic and electrochemical behaviors show a nonmonotonic change with Cu doping content. The transmittance modulation increases from 54.56% to 67.72% with the doped Cu/Ni molar ratio increasing from 0 to 0.5%, and the corresponding coloration/bleaching time reduces from 10.4/7.9 s to 6.0/4.1 s, then gets worse with the further Cu doping because of the ionized impurity scattering effects. The optimal electrode with Cu doping of 0.5% show a good cyclic stability, which maintains 84.4% of ΔT after 200 discharge/charge cycles, the excellent cycle performance can be attributed to the inhibition of the irreversible transition of Ni2+ to Ni3+ by the doping of Cu during cycling.

Thickness-controlled porous hexagonal NiO nanodiscs electrodes for use in supercapacitors: How nanodiscs thickness influences electrochemical performance

Two-dimensional (2D) nickel oxide (NiO) hexagonal nanodiscs were synthesized via a hydrothermal route, followed by successive calcination. The decisive roles of the [OH−]/[Ni2+] molar ratios, as well as the calcination temperatures, were found in controlling the nanodiscs morphology of the NiO nanostructures. The increase in the concentration of OH− ions in the precursor solution influenced the crystal growth that directed to the formation of the hexagonal nanodisc morphology with increased edge thickness and beyond certain limits transformation from the nanodiscs to complete 3D morphology. The nanodiscs grew with increasing exposed surface size with a high BET area and varied thicknesses from 4 to 20 nm. The increase in calcination temperature improved crystallinity by eliminating crystal defects and voids, while crystals grew along the (200) plane. However, a reduction in the BET area and pore volume occurred at higher calcination temperature because of the collapse in micro-mesopores. The electrochemical performances of NiO electrodes show dependence on the thickness of the nanodiscs, the calcination temperature, and the type of current collector used. A distinct electrochemical feature was observed for NiO nanodiscs over planar conductive carbon fiber paper and 3D porous Ni foam substrates. The hydrothermal approach reported here to produce thickness-controlled NiO nanodiscs with high intrinsic surface area has great potential for developing next-generation battery-type faradic electrodes in conjunction with carbon allotropes and other metal oxide materials for high power and energy density throughput.

Designing of carbon fiber cloth supported 3D porous nickel oxide composite as high-performance flexible anode for sodium- and lithium-ion batteries

Two-dimensional (2D) plate-like porous NiO–Ni2O3 nanostructure (NS) arrays are successfully deposited over the carbon fiber cloth (CF) via a hydrothermal method, followed by calcination. Hybridization of 2D plate-like porous NiO–Ni2O3 NS with CF created 3D porous CF@NiO–Ni2O3 hybrid composite (HC) (binder-free) which was investigated as an anode material for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The powder NiO–Ni2O3 NS (with binder) anode delivered discharge capacities of 15.56 and 21.6 mA h g−1 for SIBs and LIBs, respectively over 200 cycles at 100 mA g−1. After the hybridization with CF (i.e., 3D porous CF@NiO–Ni2O3 HC), its reversible capacities were further improved, exhibiting 594 and 1076 mA h g−1 for SIBs and LIBs, respectively at 100 mA g−1 over 200 cycles. The LIB coin-type full cell showed an excellent lithium storage performance, and the pouch-type full cell LIB was successfully operated, indicating its flexibility in flat, bending, rolling, and folding configurations. Benefiting from the porous 2D NS of binder-free NiO–Ni2O3 as well as the high conductivity of CF, the assembled battery revealed excellent electrochemical performance in terms of high reversible capacity and good rate capability. The excellent electrochemical characteristics of the 3D porous CF@NiO–Ni2O3 HC electrode make it a promising anode material for high-performance SIBs and LIBs.

Fabrication of Ni-NiO Foams by Powder Metallurgy Technique and Study of Bulk Crushing Strength

Despite the importance of Nickel Oxide (NiO) in diverse functional applications, very little information is available on the mechanical properties of bulk or porous NiO or, mostly unnoticed. In this study, porous Ni-NiO foam was synthesized using space holding-powder metallurgy and sintering methods to produce opened-cell structure with macrogravel and Neolamarckia cadamba (Cadamba flower) like surface morphology. Four different types of porous Ni-NiO with different pore diameter of 35.65 ± 12.77, 36.10 ± 8.85, 68.20 ±7.36 and 62.45 ± 17.48 µm were fabricated for evaluating the effect of porosity on the mechanical properties of bulk porous Ni-NiO foam. The mechanical properties such as bulk crushing force of as synthesized Ni-NiO foam with various porosities such as 20.55, 27.35, 27.85 and 28.82 % exhibited the average crushing load of 115.40, 39.95, 138.10 and 151.20 N, respectively. This study suggests that crushing load of Ni-NiO foam is not only depending on the porosity but also on the sintering temperature and crystallite sizes of NiO. HIGHLIGHTS Ni-NiO foam is synthesized using space holding-powder metallurgy and sintering methods Different pore diameter is fabricated for evaluating the effect of porosity on the mechanical properties of bulk porous Ni-NiO foam Crushing strength of Ni-NiO foam is not only depending on the porosity but also on the sintering temperature and crystallite sizes of NiO GRAPHICAL ABSTRACT