Porous NiO Nanosheets Research Articles

Design of Hierarchical Nickel-Cobalt Phosphide/Nickel Oxide with Tunable Electronic Structure and Strong Chemical Interface for Advanced Supercapacitors

The design of a reasonable heterostructure electrode to achieve enhanced areal performance for supercapacitors remains a great challenge. Here, we constructed hierarchical porous NiCoP/NiO nanocomposites anchored on Ni foam with tunable electronic and structural properties, as well as robust interfacial interaction. In NiCoP/NiO, the interconnected NiO nanosheets serve as a carrier with enriched anchoring sites to confine the NiCoP and improve its stability. Meanwhile, the ultrathin NiCoP nanosheets with bimetallic centers are connected with porous NiO nanosheets to form a reliable heterojunction, enhancing the electrochemical reaction kinetics. Taking advantage of the synergistic contribution of bimetallic centers, phosphides and unique structure, the NiCoP/NiO delivers a high areal specific capacitance (1860 mF cm−2 at 5 mA cm−2), good rate performance of 78.5% at six times the increased current density, and remarkable durability (11.0% decrease after 10,000 cycles). Furthermore, the assembled hybrid supercapacitor NiCoP/NiO//porous-activated carbon (PAC) delivers a high areal energy density of 173.7 μWh cm−2 (116.4 μWh cm−2) at 1.6 mW cm−2 (32 mW cm−2). The results indicate that the design of the heterostructure interface with strong chemical interface and tunable electronic structure is an effective and promising approach to boost the electrochemical performance for advanced supercapacitors.

Crystal facets-controlled NiO/SnO2 p-n heterostructures with engineered surface and interface towards triethylamine sensing

Crystal facets engineering is an effective means to improve the gas sensing performance of metal oxides and has become a research hotspot recently. However, research on crystal facets engineering are mainly focused on single metal oxides semiconductor, there are still very limited report about the crystal facets engineering on the semiconductor p-n heterostructures. In the present study, NiO/SnO2 p-n heterostructures were constructed by wrapping SnO2 nanocrystals exposing different crystal facets with 2D porous NiO nanosheets networks. It was found that the heterostructures with coexisted SnO2 {221} and {110} crystal facets displayed a significantly improved triethylamine sensing performance with a high response value of 78.5 towards 100 ppm triethylamine, together with ultrafast response characteristics (< 3 s), excellent stability and selectivity. The related mechanism was described through theoretical calculation. On the one hand, {221} crystal facets had higher activity and provided more active sites for the surface adsorption of triethylamine. On the other hand, the strong electron interaction between {110} facets and NiO was favorable for efficient electron transfer in interface, which further enhanced the gas sensing activity of heterostructures. This study provides a new idea for improving the gas sensing performance of metal oxide heterostructures through collaborative optimization of surface and interface.

Nitrogen doped 2D-3D network structure CMN/NiO composite for high-performance hybrid supercapacitors

In order to reduce the dense stacking of NiO nanosheets to obtain higher capacity and energy density, using CNT@mSiO2@NC (CMN) nanotubes as the substrate and urea as the precipitant, porous NiO nanoflowers and nanosheets were successfully grown between CMN nanotubes (CMN/NiO) by solvothermal method to control the morphology. The N-doped porous CMN/NiO composite obtains a high reversible capacity of 529 F g−1 in 6 M KOH electrolyte, and the capacity cycling retention rate reach 119.84% after 5000 cycles of 20 A g−1. The characteristic mesh-flake/sheet structure and the synergistic effect between components fully expose the electrochemically active sites in CMN/NiO and improve it utilization during charging-discharging, and the N atom doping enhances the electrical conductivity of CMN/NiO. The assembled asymmetric supercapacitor has a voltage window of up to 2.0 V, and an energy density performance of 26.27 Wh kg−1 at a power density of 800 W kg−1. This special structural design improves the specific capacitance, electrical conductivity, energy density and cycling stability of the electrode material compared to NiO.

High performance acetone gas sensor based on ultrathin porous NiO nanosheet

This paper discusses the direct fabrication of ultrathin Ni(OH)2 nanosheets on substrates via a facile solvothermal process, which is free from the use of additional surfactants. The precursor is converted into porous NiO nanosheets via heat treatment. The thickness and morphology of the nanosheets is controlled by manipulating the ethanol content in the solvent. The acetone sensing performance of all samples has been evaluated, as observed, the 75% ethanol-based NiO gas sensor (NiO-75), demonstrates ultrahigh acetone sensitivity, the response value can reach 60%, when the NiO nanosheet sensor detects 100 ppb acetone gas, ultralow detection limit (0.8 ppb acetone), and good stability. The excellent sensing performance of the NiO nanosheets can be attributed to their porous structure, which provides a large surface area and crystal facet with affinity to acetone gas. Moreover, the porous structure facilitates the diffusion of gas samples and products to improve the acetone detection sensitivity. Furthermore, the NiO-75 sensor demonstrates superior acetone selectivity, against other interfering gases. The findings of this study indicate that low cost NiO nanosheets fabricated via a simple process could be considered as potential, candidates for use in commercial acetone sensing applications.,

High-performance supercapacitor based on a ternary nanocomposites of NiO, polyaniline, and Ni/NiO-decorated MWCNTs

BackgroundAlthough high theoretical capacitance, low cost, and superior cycling reversibility make NiO a promising material for preparing supercapacitors, poor conductivity and ionic transport have limited its applicability. MethodsTo overcome these drawbacks, in this study we prepared ternary composites from porous NiO nanosheets, polyaniline:poly(sodium 4-styrenesulfonate) (PANI:PSS), and Ni/NiO-decorated multiwalled carbon nanotubes (MWCNTs). Using a spray-drying technique, the conductive PANI:PSS was bound tightly to the porous NiO nanosheets to form PANI:PSS/NiO (P-NiO) microspheres. Here, the PANI:PSS infiltrated the nanopores of NiO and modified the NiO surface, thereby decreasing the internal resistance and avoiding restacking of the NiO nanosheets. Moreover, we synthesized MWCNTs decorated with Ni/NiO dual-phase nanoparticles; here, the deposition of the Ni/NiO nanoparticles improved both the electrical conductivity and capacitive behavior of the MWCNTs. Significant findingsAs a result, the modified MWCNTs (m-MWCNTs) functioned as a novel additive that lowered the external resistance among the P-NiO microspheres. An asymmetric supercapacitor employing the designed ternary system and active carbon as electrodes achieved a remarkable specific capacitance of 105.6 F/g at 0.5 A/g, a maximum energy density of 33 W h/kg, and superior cycling stability.

Hetero-epitaxy growth of cobalt oxide/nickel oxide nanowire arrays on alumina substrates for enhanced ethanol sensing characteristics

In this work, Co3O4 nanowire arrays are prepared in-situ on the flat alumina substrates via a simple hetero-epitaxial growth without adding seed layers. It is found that the density of Co3O4 nanowires can be regulated by varying the concentration of NH4F that acts as substrate activation promoting the formation of nuclei on alumina substrate. In order to improve the gas-sensing performance, porous NiO nanosheets are anchored on the surface of Co3O4 nanowire arrays to form a novel heterostructure (Co3O4/NiO). Gas-sensing tests indicate a higher response value of these array composites towards ethanol (Rg/Ra = 4.26) than that of pristine Co3O4 nanowire arrays (Rg/Ra = 1.27) and NiO nanosheets (Rg/Ra = 1.89). The improved gas-sensing performances resulting from the special array structures and novel heterojunctions can provide abundant diffusion channels for gas molecules as well as a synergistic effect between Co3O4 and NiO.

Dispersed and spherically assembled porous NiO nanosheets for low concentration ammonia gas sensing applications

Resistor-type ammonia gas sensors with different architectures of porous NiO nanosheets are comprehensively studied and demonstrated for their sensing characteristics. During the synthesis process, the amount of nickel nitrate hexahydrate can vary the morphology of NiO nanostructure. Holes on the NiO nanosheets increase the surface area of the material and enhance the sensing performances of the sensor. Among the different sensors, dispersed distribution has more surface area to react with ammonia gas. Experimentally, the dispersed porous NiO nanosheets ammonia gas sensor exhibits higher sensing response ratio of 87.17% to 15 ppm NH3 gas under 150 °C. Fast response time and high response ratio to low concentration ammonia gas are shown in the dispersed sensor. Based on the advantages of its simple structure and relatively easy fabrication, the material is beneficial to accurate ammonia sensing applications.

Inherently porous Co3O4@NiO core–shell hierarchical material for excellent electrochemical performance of supercapacitors

Supercapacitors have become a highly appealing candidate for next-generation energy storage system due to their high power density and long operation life. However, insufficient active materials utilization leads to a relatively low specific capacitance, which poses a significant challenge to their practical applications. In our work, hierarchical nanostructure with intrinsic porous NiO nanosheets uniformly dispersion on Co3O4 backbone is prepared through a facile and environmentally friendly method (denoted as Co3O4@NiO-X). The resulting well-defined porous core–shell material (Co3O4@NiO-1) displays a three-dimensional architecture, convenient ion transport channel and more exposed surface area, which demonstrates a significantly enhanced pseudocapacitance performance, with a high specific capacitance (692.8 F/g at a current density of 1 A/g) and excellent cycling performance (90.88% of initial value is retained after 2500 cycles). Furthermore, an asymmetric supercapacitor (ACS) is fabricated by employing Co3O4@NiO-1 core–shell material as positive electrode, activated carbon (AC) as negative electrode and 6 M KOH as electrolyte, which represents an excellent specific capacitance of 68.1 F/g (at 1 A/g) and provides high energy density of 35 Wh/kg at the power density of 540 W kg−1, 23.4 Wh/kg at higher power density of 2722.1 W/kg, together with exceptional cyclic stability of 90.83% after 3000 cycles. The excellent electrochemical performance of Co3O4@NiO-1 materials demonstrates that rational design of porous core–shell structure can be a general strategy for multi-component materials to realize electrochemical energy storage devices with excellent performance.

Magnetic and Optical Field Multi-Assisted Li-O2 Batteries with Ultrahigh Energy Efficiency and Cycle Stability.

The photoassisted lithium-oxygen (Li-O2 ) system has emerged as an important direction for future development by effectively reducing the large overpotential in Li-O2 batteries. However, the advancement is greatly hindered by the rapidly recombined photoexcited electrons and holes upon the discharging and charging processes. Herein, a breakthrough is made in overcoming these challenges by developing a new magnetic and optical field multi-assisted Li-O2 battery with 3D porous NiO nanosheets on the Ni foam (NiO/FNi) as a photoelectrode. Under illumination, the photogenerated electrons and holes of the NiO/FNi photoelectrode play a key role in reducing the overpotential during discharging and charging, respectively. By introducing the external magnetic field, the Lorentz force acts oppositely on the photogenerated electrons and holes, thereby suppressing the recombination of charge carriers. The magnetic and optical field multi-assisted Li-O2 battery achieves an ultralow charge potential of 2.73 V, a high energy efficiency of 96.7%, and good cycling stability. This external magnetic and optical field multi-assisted technology paves a new way of developing high-performance Li-O2 batteries and other energy storage systems.

High-loading Co-doped NiO nanosheets on carbon-welded carbon nanotube framework enabling rapid charge kinetic for enhanced supercapacitor performance

Developing high power and energy supercapacitors (SCs) is a long-pursued goal for the application in transportation and energy storage station. Herein, a rationally-designed Co-doped nickel oxide nanosheets@carbon-welded carbon nanotube foam (Co-doped NiO@WCNTF) as freestanding electrode is successfully prepared for high power and energy SCs. The WCNTF framework with high specific surface area provides three dimensional highly conductive network for fast charge transport and ensures high loading of active materials (9.2 mg/cm 2 ). Moreover, porous Co-doped NiO nanosheets uniformly anchored on the WCNTF framework enable rapid charge kinetics due to the high intrinsic conductivity of Co-doped NiO nanosheets and their good contact with conductive WCNTF substrate. As a result, the unique integrated electrode with 3D architecture exhibits an ultrahigh specific capacitance of 11.45 F/cm 2 at 5 mA/cm 2 , outstanding rate capability (11.45 F/cm 2 at 5 mA/cm 2 and a capacitance retention of 86.2% at 30 mA/cm 2 ) and good cycling stability, suggesting great potential for high performance supercapacitor. A high-loading binder-free Co-doped NiO@WCNTF (9.2 mg/cm 2 ) electrode with 3D architecture, high ionic and electronic conductivity is successfully synthesized, showing an ultrahigh specific capacitance, outstanding rate capability and good cycling stability.

Bifunctional Oxygen Electrocatalyst of Mesoporous Ni/NiO Nanosheets for Flexible Rechargeable Zn\u2013Air Batteries

HighlightsAn oxygen electrocatalyst consisting of Ni nanoparticles interpenetrated in porous NiO nanosheets was successfully synthesized.The liquid Zn–air battery reveals a large open-circuit potential of 1.47 V, the maximum power density at 225 mW cm−2, and excellent device stability of over 120 h.The flexible solid-like rechargeable Zn–air battery shows excellent stability (no evident weakening after 240 cycles) and bendability.

Construction of porous LaFeO3 microspheres decorated with NiO nanosheets for high response ethanol gas sensors

Designing novel structural constructions and adopting appropriate catalyst materials are the key to overcoming inherent limitations of metal oxide gas sensors. In this paper, porous LaFeO3 microspheres decorated with NiO nanosheets were prepared by simple hydrothermal method, and the p-p heterojunction was successfully constructed. Characterization results showed that the NiO nanosheets were uniformly grown on the surface of the porous LaFeO3 microspheres and the size of nanosheets was very uniform. This kind of morphology effectively improves the contact area between metal oxides and the target gases. Gas-sensing tests revealed that the combination of porous LaFeO3 microspheres and NiO nanosheets endows superior ethanol sensing performance with high response, good selectivity and rapid responding and recovering speed. The well-defined NiO@LaFeO3 nanocomposites offered unique hierarchical structure and p-p junctions at the heterointerfaces, which could induce the large hole depletion regions and hence benefited for oxygen adsorption and gas-sensing reactions at the interfaces. This work not only demonstrates the NiO@LaFeO3 nanocomposite is a promising material for fabricating ethanol sensors but also provides a useful guidance for design well-defined core@shell p-p heterojucntions in gas-sensing applications.

3D porous ZnCo2O4@NiO on nickel foam as advanced electrodes for lithium storage

An advanced binder-free electrode of hierarchical porous ZnCo2O4@NiO/nickel foam (NF) was designed and synthesized by using 3D porous ZnCo2O4 cubes anchored on ordered porous NiO nanosheets in situ grown on NF. The ZnCo2O4@NiO/NF not only can effectively improve the binder force of ZnCo2O4 on NF to decrease contact resistance and dusting but also can alleviate volume change of ZnCo2O4 matrix in the cycles. The advanced ZnCo2O4@NiO/NF as anode materials for lithium-ion batteries delivered remarkable cycling ability of 730.5 mAh g−1 at 800 mA g−1 after 200 cycles and superb rate performance of 762.4 mAh g−1 at 1600 mA g−1. The excellent electrochemical performance of ZnCo2O4@NiO/NF electrode demonstrates its great potential for use in Li-ion batteries.

Bifunctional Electrocatalytic Activity of Nitrogen-Doped NiO Nanosheets for Rechargeable Zinc-Air Batteries.

In order to improve the efficiencies and service lifetimes of rechargeable Zn-air batteries, it is necessary to develop highly efficient air electrocatalysts. In the present study, we prove that the bifunctional electrocatalytic activity in NiO nanosheets is effectively improved by the synergistic effects of N dopants and considerably porous structure. As an electrocatalyst for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), the as-prepared porous N-doped NiO nanosheets exhibit good activities with the small overpotential and ideal half-wave potential, which is superior to Ir/C electrocatalyst. Besides, it is proved that the process of HO* being oxidized to O* is the OER potential rate-determining step; also the OER electrocatalytic performance of NiO can be markedly promote by the doping of N atoms using the density functional theory calculations. Furthermore, the fabricated Zn-air battery based on the porous N-doped NiO nanosheets also exhibits superior activities, outperforming many reported NiO-based electrocatalyst materials. Two series Zn-air cells with a voltage of 2.80 V can power a red light-emitting diode, which shows their large potential for various applications.

Spray-dried nanoporous NiO/PANI:PSS composite microspheres for high-performance asymmetric supercapacitors

In this study, we used a spray-drying method to synthesize a hierarchically structured binary nanocomposite comprising highly porous NiO nanosheets and polyaniline:poly(sodium 4-styrenesulfonate) (PANI:PSS) materials. In this system, the porous NiO nanosheets—obtained through thermal decomposition of β-Ni(OH)2 derived from microwave-assisted hydrothermal treatment—dispersed well in the PANI:PSS solution. The homogeneous suspension was then processed through spray-drying and crosslinking of PANI:PSS and GOPS to form NiO/PANI:PSS microspheres. The PANI polymer served as a good conductor and thin spacer that prevented the NiO nanosheets from undergoing layer-to-layer stacking. Moreover, the crosslinked PANI:PSS acted as a binder that held all of the active materials together, leading to high mechanical integrity and excellent water-resistance. Through a synergistic effect in this unique nanoarchitecture, the NiO/PANI:PSS nanocomposite displayed a higher capacitance (834 F/g) at 1 A/g compared with that of NiO (380 F/g) and PANI:PSS (264.5 F/g) individually. Furthermore, the NiO/PANI:PSS composite displayed remarkable rate performance and outstanding cycling life—88.9% retention of specific capacitance after 3000 repeated charge/discharge tests—as a result of its low resistance and high (SSA). We fabricated asymmetric supercapacitors (ASCs) incorporating NiO/PANI:PSS and active carbon (AC) to further explore the capacitive performance of the composite. The as-fabricated devices also delivered remarkable performance, with an energy density of 32.84 Wh/kg, a power density of 375 W/kg, and excellent cycle life.

Novel porous ultrathin NiO nanosheets for highly efficient water vapor adsorption-desorption

Exploiting humidity-buffering materials for air humidity control is of vital necessities. Novel porous ultrathin NiO nanosheets as effective humidity-buffering materials were successfully synthesized with a simple, low-cost and high-yield method. It exhibits ultrahigh water vapor adsorption-desorption performance at room temperature, which is superior to both commonly used conventional materials and most reported novel ones. The excellent water vapor adsorption capacity can be attributed to its unique porous ultrathin structures. Numerous mesopores with relatively large diameter and volume can largely decrease water molecules diffusion resistance and increase adsorption space. Moreover, the ultrathin structure can lead to more sufficient contact between water vapor and adsorbents and provide great specific surface area, which can further facilitate water vapor adsorption. The potential of ultrathin nanosheets to be humidity-buffering materials has been explored carefully for the first time and this work also sheds light on the rational design of adsorbents with superior water capacity for efficient humidity control.

Self‐Assembly of Lotus‐Type Holes Two‐Dimensional NiO Nanosheets and Its Efficient Catalytic Property for Styrene Epoxidation

AbstractLotus‐type holes two‐dimensional NiO nanosheets were fabricated via hydrothermal method followed by calcinations. Three types of surfactants as the structure‐directing agent in an ammonia aqueous solution with calcination, only anionic surfactant sodium dodecyl benzene sulfonate (SDBS), non‐ionic surfactant polyvinyl pyrrolidone (PVP) can form lotus‐type porous NiO nanosheets, cationic surfactant cetyltrimethyl ammonium bromide (CTAB) have no such effect. A series of characterization of the resulting samples revealed that the materials maintained singularly small thickness of only 3–5 nm, lotus root hole diameter 40 nm(SDBS),20 nm(PVP). The formation mechanism of the lotus‐type porous two‐dimensional morphology is investigated. The as‐synthesized NiO without support delivered efficient catalytic property in styrene epoxidation which significantly reduced reaction time. When the catalyst was reused the conversion and selectivity of styrene oxide still remained high.

Freestanding Three-Dimensional CuO/NiO Core\u2013Shell Nanowire Arrays as High-Performance Lithium-Ion Battery Anode

We demonstrate significant improvement of CuO nanowire arrays as anode materials for lithium ion batteries by coating with thin NiO nanosheets conformally. The NiO nanosheets were designed two kinds of morphologies, which are porous and non-porous. By the NiO nanosheets coating, the major active CuO nanowires were protected from direct contact with the electrolyte to improve the surface chemical stability. Simultaneously, through the observation and comparison of TEM results of crystalline non-porous NiO nanosheets, before and after lithiation process, we clearly prove the effect of expected protection of CuO, and clarify the differences of phase transition, crystallinity change, ionic conduction and the mechanisms of the capacity decay further. Subsequently, the electrochemical performances exhibit lithiation and delithiation differences of the porous and non-porous NiO nanosheets, and confirm that the presence of the non-porous NiO coating can still effectively assist the diffusion of Li+ ions into the CuO nanowires, maintaining the advantage of high surface area, and improves the cycle performance of CuO nanowires, leading to enhanced battery capacity. Optimally, the best structure is validated to be non-porous NiO nanosheets, in contrary to the anticipated porous NiO nanosheets. In addition, considering the low cost and facile fabrication process can be realized further for practical applications.

Correction to “Phosphorus and Aluminum Codoped Porous NiO Nanosheets as Highly Efficient Electrocatalysts for Overall Water Splitting”

Correction to “Phosphorus and Aluminum Codoped Porous NiO Nanosheets as Highly Efficient Electrocatalysts for Overall Water Splitting”

Phosphorus and Aluminum Codoped Porous NiO Nanosheets as Highly Efficient Electrocatalysts for Overall Water Splitting

We present a facile way to fabricate phosphorus and aluminum codoped nickel oxide-based nanosheets by using layered double hydroxide (AlNi-LDH) as precursors, which showed an overall water-splitting performance in alkaline solution. The codoping of phosphorus and aluminum into nickel oxide nanosheets leads to an optimum balance among surface chemical state, electrochemically active surface area, and density of active sites. As a result, it can afford a current density of 100 mA cm–2 at the overpotential of 310 mV for oxygen evolution reaction (OER) and a current density of 10 mA cm–2 at the overpotential of 138 mV for hydrogen evolution reaction (HER) in 1 M KOH. When it was used as a bifunctional catalyst in a two-electrode water-splitting device, a potential of 1.56 V was achieved at the current density of 10 mA cm–2.