Nanoporous Nickel Oxide Research Articles

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.

Nanoporous ALD-modified oxygen-deficient NiO flakes as anodes for lithium-ion batteries

The flake-like nature of materials possessing continuous porous skeletons makes them naturally suited for energy storage and other applications. Nickel oxide (NiO) stands out as a highly attractive anode material for lithium-ion batteries due to its relatively high theoretical specific capacity. Nevertheless, the sluggish kinetics of its reactions and significant volume variations during cycling curtail its rate capability and electrochemical stability. In this work, we successfully fabricate nanoporous oxygen-deficient NiO@Al2O3 flakes by a multi-step process involving magnetron sputtering deposition, subsequent thermal oxidation treatment, and a particle atomic layer deposition surface coating technique. The resultant nanoporous oxygen-deficient NiO@Al2O3 flakes demonstrate the potential to establish an intricate network that facilitates efficient charge transfer, rapid ion diffusion, and mechanical robustness throughout electrochemical processes. Particularly noteworthy is the role of the ultrathin Al2O3 coating, which greatly bolsters the cycle life. When employed as lithium storage materials, the nanoporous NiO@Al2O3 flakes exhibit remarkable attributes, including high specific capacity (720 mAh g−1 at 25 mA g−1), superior rate capability (300 mAh g−1 at 5000 mA g−1) and sustained cycling ability, showcasing a reversible capacity of 413 mAh g−1 after 500 cycles at 150 mA g−1 (equivalent to a duration exceeding 4 months). Moreover, the distinctive morphologies and compositions observed after extended cycles definitively corroborate the efficacy of the nanoporous flake architecture. Finally, we present a full-cell configuration comprising a NiO@Al2O3 flakes anode paired with a LiNi0.8Mn0.1Co0.1O2 cathode, which notably exhibits remarkable cycle stability, retaining 84.2 % of its capacity after 100 cycles at 200 mA g−1. This effective and versatile strategy might hold promise for extension to alternative anode and cathode materials, potentially enabling enhanced specific capacity and rendering them suitable for energy storage applications.

Morphology effects on electrocatalysis of anodic water splitting on nickel (II) oxide

Oxygen evolution reaction (OER) is critical for producing high purity hydrogen and oxygen via electrocatalytic water splitting. In this work, single crystalline, nanoporous nickel oxide (NiO) was prepared using a hydrothermal, soft-templated synthesis route followed by calcination at different temperatures. It is shown that the NiO crystals have a cubic lattice, and the pore size can be tuned from ∼1 to ∼70 nm by varying the calcination temperature, i.e. variation from micro to macroporosity. The NiO's catalytic performance as electrocatalysts was evaluated in OER, both thermodynamically and kinetically. Mesoporous NiO with calcination temperature of 400 °C had the lowest overpotential (335 mV) required @ 10 mA/cm2 accompanied with the highest turnover frequency value and mass activity among of the obtained NiO electrocatalysts. The study shows that the electrocatalytic activity of nanoporous NiO outperforms that of commercial catalyst Ir/C (∼360 mV @ 10 mA/cm2). Microporous NiO possess the highest specific surface area and electrical double layer capacitance, while the nonporous NiO particles have the highest specific activity and BET activity of the catalysts. It is concluded that the minimization of voltage losses by the nanoscale enlargement of the electrocatalyst surface area shows the coherence between gas adsorption and electrocapacitive measurements. Conversely, the OER kinetics showed deterioration with surface area maximization due to the impediment of ionic transport inside the micropores. This work demonstrates the importance of morphology optimization to obtain an efficient OER electrocatalyst with low required overpotential and kinetic loss.

Chemical Analysis of Sol Gel Technology and Technical Evaluation of the Related Novel Applications

The sol gel technology is useful for growing of thin films on large objects of any shape, and synthesizing ceramic materials of very high purity and homogeneity, at room temperature. Though, it is a quite old technique, but recently has drawn lot of attentions, as the technique is handy for coating the interiors of the objects, and also does not require the sophisticated coating units. The Sol Gel Technology use for the fabrication of thin films of nanoporous Nickel oxide (np-NiOx), have tremendous applications in increasing the efficiency of Perovskite Solar Cells, Which are renewable source of energy. The purpose of the present paper is to provide the theoretical analysis of sol gel technology. Besides giving a brief technical review of the important recent investigations, it has also focused on the novel applications of Sol Gel Technology to improve properties of thin layer coatings including optical coatings, high transmitting coatings and high reflection coatings.

Performance Comparison between the Nanoporous NiO x Layer and NiO x Thin Film for Inverted Perovskite Solar Cells with Long-Term Stability.

The development of hole-transport layers (HTLs) that elevate charge extraction, improve perovskite crystallinity, and decrease interfacial recombination is extremely important for enhancing the performance of inverted perovskite solar cells (PSCs). In this work, the nanoporous nickel oxide (NiOx) layer as well as NiOx thin film was prepared via chemical bath deposition as the HTL. The sponge-like structure of the nanoporous NiOx helps to grow a pinhole-free perovskite film with a larger grain size compared to the NiOx thin film. The downshifted valence band of the nanoporous NiOx HTL can improve hole extraction from the perovskite absorbing layer. The device based on the nanoporous NiOx layer showed the highest efficiency of 13.43% and negligible hysteresis that was better than the one using the NiOx thin film as the HTL. Moreover, the PSCs sustained 80% of their initial efficiency after 50 days of storage. This study provides a powerful strategy to design PSCs with high efficiency and long-term stability for future production.

Utilization of Nanoporous Nickel Oxide as the Hole Injection Layer for Quantum Dot Light-Emitting Diodes.

Nickel oxide (NiOx) has been extensively investigated as the hole injection layer (HIL) for many optoelectronic devices because of its excellent hole mobility, high environmental stability, and low-cost fabrication. In this research, a NiOx thin film and nanoporous layers (NPLs) have been utilized as the HIL for the fabrication of quantum dot light-emitting diodes (QLEDs). The obtained NiOx NPLs have spongelike nanostructures that possess a larger surface area to enhance carrier injection and to lower the turn-on voltage as compared with the NiOx thin film. The energy levels of NiOx were slightly downshifted by incorporating the nanoporous structure. The amount of Ni2O3 species is higher than that of NiO in the NiOx NPL, confirming its good hole transport ability. The best QLED was achieved with a 30 nm thick NiOx NPL, exhibiting a maximum brightness of 68 646 cd m–2, a current efficiency of 7.60 cd A–1, and a low turn-on voltage of 3.4 V. More balanced carrier transport from the NiOx NPL and ZnO NPs/polyethylenimine ethoxylated (PEIE) is responsible for the improved device performance.

Nanoporous nickel oxide catalyst with uniform Ni dispersion for enhanced hydrogen production from organic waste

In this report, we propose magnetically separable porous nickel oxide nanostructure with uniform Ni distribution having the large surface area and atomically dispersed Si sites for enhanced hydrogen production from organic waste. The catalyst showed ten times higher production rate from volatiles during carbonization of organic waste and coal than that in the absence of the catalyst. The reduced Ni/NiO catalyst yielded two times higher hydrogen production compared to the traditional Ni/Al2O3 catalyst. The highest yield of hydrogen over reduced Ni/NiO was 32 g/kgfeed at 600 °C in fixed bed reactor via pyrolysis-reforming of bagasse. The Ni/NiO showed far more efficient recyclability compared to traditional Ni/Al2O3. The economic aspect of the Ni/NiO catalyst was compared with the Ni/Al2O3 catalyst based on H2 yield. TGA and TPO analysis confirmed the presence of amorphous coke.

The Effect of Trap States on the Optoelectronic Properties of Nanoporous Nickel Oxide

Nickel oxide (NiO) is often used as a hole-transporter material in both photovoltaic and photoelectrochemical solar cells. As a result of the reversible nickel(II)/(III) transformation, it is also electrochromic. These potential-dependent optoelectronic properties of this intriguing material, however, are yet to be fully understood. In this article, we show that the picture is more complicated than the generally discussed nickel(II)/(III) transformation, because of the presence of trap states. We reveal that the density of states is directly influenced by the applied potential in nanoporous NiO films; and show how it manifests in the electrical properties and Raman spectral features. We demonstrated that the population/depopulation of shallow trap states has an important role in dictating these changes. The presented insights can also contribute to the better understanding of the optoelectronic properties of different semiconductor electrodes under charging conditions.

Efficiency enhancement of electrochromic performance in NiO thin film via Cu doping for energy-saving potential

Construction of low-cost and high-efficiency electrochromic electrodes with high color contrast and fast response time in electrochromic applications have led to a proliferation of studies in metal oxides. This research study presents a comprehensive overview of the electrochemical synthesis of nanoporous Cu-doped nickel oxide films on ITO-coated glass substrate and its electrochromic behavior in alkaline medium. X-ray diffraction analysis and scanning electron microscopy are used to determine the phase and morphology of the produced films. The films indicate uniform and good adhesion to the substrate. The electrochromic behavior of the deposited films is tested by means of cyclic voltammetry, chronocoulometry, repeating chronoamperometry, and electrochemical impedance spectroscopy measurements. The color change from dark brown to transparent appears reversibly well suitable under sequential potential from −0.2 to +1.0 V. After the Cu atoms incorporate into the host NiO matrix, noticeably enhancements are observed in optical modulation (57.1% at 550 nm), coloration efficiency (13.78 cm2/C) and response time (tb = 2.26 s and tc = 1.77 s) compared to its as-prepared NiO films. Energy level diagrams including fermi level, valance band edge and conduction band edge positions are presented based on the Mott-Schottky approximation and Tauc’s method using absorbance data for the NiO and Cu:NiO films. The negative slope of the Mott-Schottky plot shows p-type conductivity for the films, and acceptor density is found as 4.44×1019 cm−3 and 5.41×1019 cm−3 for the NiO and Cu:NiO films, respectively. An equivalent electronic circuit is fitted using the measured Nyquist data of the NiO or Cu:NiO semiconductor/electrolyte system, and the calculated values of the circuit elements show significant sensitivity to the Cu doping. Therefore, our results make a major contribution to the research on energy-saving smart windows by demonstrating analyses in detail.

Facile synthesis of nano dendrite-structured Ni–NiO foam/ERGO by constant current method for supercapacitor applications

This study introduces a novel, non-toxic, scalable, two-step method for the fabrication of highly nanoporous nickel and nickel oxide (Ni–NiO) foam/Electrochemically reduced graphene oxide (ERGO) electrodes with exceptional capacitance suitable for supercapacitor application. This procedure includes drop cast and graphene oxide (GO) reduction by galvanostatic process. To create the electrodes, electrodeposition process and selective electrochemical dealloying accompanied by a hydrogen evolution reaction (HER) were performed on a copper substrate. Afterwards, drop cast and galvanostatic processes were accomplished to coat GO nanosheets on Ni–NiO foam. The structure of achieved nanocomposites was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). High-specific capacitance of 1995 F g−1 at a current density of 1 A g−1 (galvanostatic charge–discharge) (GCD) was achieved for the Ni–NiO foam/electrochemically reduced graphene oxide (ERGO) electrode with excellent cycling stability. A constant, high-specific capacitance (95.1% of the initial value) was achieved after 6000 cycles at 20 A g−1.

Pulsed electrodeposition of reduced graphene oxide on Ni[sbnd]NiO foam electrode for high-performance supercapacitor

Through electrodeposition, controlling hydrogen evolution reaction and selective electrochemical dealloying of copper from NiCu porous foam, highly nanoporous nickel and nickel oxide is fabricated on the copper surface. Electrochemically reduced graphene oxide (ERGO) is loaded on the NiNiO foam as high-performance electrodes for supercapacitors through pulsed galvanostatic reduction of drop casted graphene oxide nanosheets at different duty cycles and frequencies. Surface morphology and composition of fabricated ERGO/NiNiO foam composite electrodes are characterized using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Raman Spectroscopy. Electrochemical impedance spectroscopy (EIS) measurements, galvanostatic charge/discharge (GCD) and cyclic voltammetry (CV) are carried out to study the electrochemical behavior of ERGO/NiNiO foam electrodes. From structural and electrochemical characterizations, optimized parameters for pulse duty cycle and frequency were found to be 10% and 1000 Hz, respectively. As a result, the ERGO/NiNiO foam film (ic = −10 mA/cm2, f = 1000 Hz and DC = 10%) provides a specific capacitance of 2298 F/g in 1 M KOH at a current density of 1 A/g. Stability study of fabricated film represents a long cycling life up to 4000 cycles with 0.7% decay in specific capacitance at the high current density of 20 A/g in the potential range of 0–0.6 V vs. saturated calomel electrode (SCE).

Nanoporous p-type NiOx electrode for p-i-n inverted perovskite solar cell toward air stability

Designing air-stable perovskite solar cells (PSCs) is a recent trend in low-cost photovoltaic technology. Metal oxide-based electron transporting layers (ETLs) and hole transporting layers (HTLs) have attracted tremendous attention in PSCs, because of their excellent air stability, high electron mobility, and optical transparency. Herein, we report a co-precipitation method for the synthesis of p-type nanoporous nickel oxide (np-NiOx) thin films as the HTL for inverted (p-i-n) PSCs. The best-performing p-i-n PSC having np-NiOx HTL, (FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 (herein FAPbI 3 stands for formamidinium lead iodide and MAPbBr 3 stands for methylammonium lead bromide) perovskite and phenyl-C 61 -butyric acid methyl ester (PCBM)/ZnO ETL exhibited a 19.10% (±1%) power conversion efficiency (PCE) with a current density ( J SC ) of 22.76 mA cm −2 , open circuit voltage ( V OC ) of 1.076 V and fill factor (FF) of 0.78 under 1 sun (100 mW cm −2 ). Interestingly, the developed p-i-n PSCs based on p-type NiOx and n-type ZnO could retain >80% efficiency after 160 days, which is much higher than conventional PEDOT:PSS HTL-based PSCs. Our findings provide air-stable perovskite solar cells with high efficiency.

A comparative study on the electrochemical properties of nanoporous nickel oxide nanowires and nanosheets prepared by a hydrothermal method.

Metal oxide nanostructures have been extensively used in electrochemical devices due to their advantages, including high active surface area and chemical stability. However, the electrochemical properties of metal oxides are strongly dependent on their structural characteristics. We performed a comparative study on the electrochemical performance of nanoporous nickel oxide (NiO) nanosheets and nanowires. The advanced nanoporous NiO nanomaterials were synthesized by a facile hydrothermal method followed by thermal calcination. The synthesized nanomaterials, as characterized by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, and nitrogen adsorption/desorption isotherms, demonstrated the nanoporosity and high crystallinity of the NiO nanosheets and nanowires. Cyclic voltammetry measurement was performed using a three-electrode system to evaluate the electrochemical properties of the synthesized materials. Results showed that the nanoporous NiO nanosheets possessed a higher current density than that of the nanowires by approximately ten times. Moreover, the nanoporous NiO nanosheets showed exceptionally high stability of almost 100%, after three cycles in strong alkaline environments, thereby suggesting possible application in electrochemical devices.

Investigation of dry-deposited ion storage layers using various oxide particles to enhance electrochromic performance

Various ion storage layers were fabricated on ITO-glass substrates by a dry deposition process to study their effects in electrochromic devices. Dense nickel oxide (NiO) film was formed using micro-sized NiO particles, a porous film was formed using nano-sized NiO particles, and a porous antimony tin oxide (ATO) film was formed using nano-sized ATO particles. Electrochemical analyses revealed that the nano-porous NiO layer had a high charge capacity with a low charge transfer resistance. Moreover, an electrochromic device using a NiO film with nano-sized pores had an optical transmittance difference of 42% and a stable cyclic transmittance for 1h at a wavelength of 630nm. We assessed the effects of the different ion storage layers by evaluating the electrochromic device in terms of the following important properties: 1) high charge capacity, 2) low charge transfer resistance at the interface between film and electrolyte, and 3) high diffusion rate from film to electrolyte. Based on these criteria, we found that the ion storage layer formed with nano-sized NiO particles best satisfied these conditions. Finally, we confirmed that stable and high electrochromic performance can be achieved through improving these properties in ion storage layers.

A study on characterization of nano-porous NiO thin film to improve electrical and optical properties for application to automotive glass

Nano-porous nickel oxide (NiO) film is coated on the indium tin oxide glass using nickel acetate solution containing block copolymer as the surfactant by the sol-gel method with a spin coating technique. The block copolymer assists the porosity of NiO thin film, which improves the ion intercalation and deintercalation. The electrochromic properties of NiO thin films with different thickness are investigated in an aqueous alkaline electrolyte (0.1M KOH) by means of cyclic voltammetry, chronoamperometry and transmittance measurements. The nano-porous structure of NiO thin film gives good reaction kinetics with high diffusion coefficient of 1.79×10−9cm2s−1. In the case of NiO thin film with thickness of 170nm, the electrochromic properties are observed with the coloration efficiency of 129.73cm2C−1, coloration/bleaching time of 7.95/3.33s and transmittance modulation of 28% at a wavelength of 550nm. The thinner NiO film is, the better diffusion coefficient and coloring change time are. However, the transmittance modulation and coloration efficiency of the device are better as NiO film is thicker. Therefore, it is important to optimize the electrochromic device parameters depending on application area because they are trade-off relation.

Fabrication and Super Capacitive Performance of Nanoporous Nickel Oxide Film

AbstractIn order to improve the whole performance of a single kinds of materials, the nanoporous nickel (NPN) oxide film was fabricated by the method of interfacial electroless plating. The nickel (Ni) was deposited on the surface of the substrate in three dimensional nanoporous structure, and then the surface layer of Ni is converted into nickel oxide (NiO) after exposure to oxygen in the air. The as‐prepared nickel oxide material not only maintains the porous structure of the substrate, but also increases the specific surface area of the material and improves the conductivity, thereby significantly improving the electrochemical capacitance performance of the material which characterized by X‐ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X‐ray spectrometer (EDS). The mass specific capacitance is 387 F g−1 and volumetric specific capacitance is 964 F cm−3. Therefore, the porous nickel oxide film is an electrode material with great potential for super capacitors.

Photoelectrochemical properties of mesoporous NiO x deposited on technical FTO via nanopowder sintering in conventional and plasma atmospheres.

Nanoporous nickel oxide (NiOx) has been deposited with two different procedures of sintering (CS and RDS). Both samples display solid state oxidation at about 3.1 V vs Li+/Li. Upon sensitization of CS/RDS NiOx with erythrosine b (ERY), nickel oxide oxidation occurs at the same potential. Impedance spectroscopy revealed a higher charge transfer resistance for ERY-sensitized RDS NiOx with respect to sensitized CS NiOx. This was due to the chemisorption of a larger amount of ERY on RDS with respect to CS NiOx. Upon illumination the photoinduced charge transfer between ERY layer and NiOx could be observed only with oxidized CS. Photoelectrochemical effects of sensitized RDS NiOx were evidenced upon oxide reduction. With the addition of iodine RDS NiOx electrodes could give the reduction iodine → iodide in addition to the reduction of RDS NiOx. p-type dye sensitized solar cells were assembled with RDS NiOx photocathodes sensitized either by ERY or Fast Green. Resulting overall efficiencies ranged between 0.02 and 0.04 % upon irradiation with solar spectrum simulator (Iin: 0.1 W cm−2).

Fabrication of Asymmetric Supercapacitors Based on Coordination Polymer Derived Nanoporous Materials

Considerable efforts have been devoted to the synthesis and characterization of novel nanoporous materials because of their versatile applications, such as gas storage, catalysis, and energy storage applications. Controllable synthesis of coordination polymers (CPs) with two- and three-dimensional architectures has given impetus to the development of nanomaterials with many exciting properties and applications. Here, we focus on CP-derived nanoporous materials and study their electrochemical performance as electrode materials in supercapacitors. Nanoporous carbon is prepared by simple carbonization of zinc-containing zeolitic imidazolate framework (ZIF-8). On the other hand, nanoporous nickel oxide (NiO) is prepared by thermal treatment of cyano-bridged CPs. By using the above two electrodes, we fabricate a novel asymmetric supercapacitor. These CP-derived nanoporous materials exhibit excellent electrochemical performance with high specific energy and specific power, and excellent cycling stability.

Nanoporous NiO Plates with a Unique Role for Promoted Oxidation of Carbonate and Carboxylate Species in the Li–O2 Battery

We report a novel catalytic reaction to promote oxidation of carbonate and carboxylate species using nanoporous nickel oxide (NiO) in the lithium–oxygen (Li–O2) battery. These nanoporous NiO catalysts in the shape of two-dimensional (2-D) hexagonal plates are incorporated on the carbon nanotube (CNT) electrode, which remarkably enhances oxidation efficiency of carbonate and carboxylate species as representative side products in Li–O2 electrochemistry and greatly improves the cycleability to more than 70 cycles. The oxidation reaction predominantly occurs at the nanoporous NiO, toward which the carbonate and carboxylate species may migrate for the complete decomposition. This result is notably distinguished from a NiO-free CNT electrode, where such a passivation layer becomes thicker and precludes electron transfer, thus inducing poor cyclability.

Controlled synthesis of nanoporous nickel oxide with two-dimensional shapes through thermal decomposition of metal-cyanide hybrid coordination polymers.

The urgent need for nanoporous metal oxides with highly crystallized frameworks is motivating scientists to try to discover new preparation methods, because of their wide use in practical applications. Recent work has demonstrated that two-dimensional (2D) cyanide-bridged coordination polymers (CPs) are promising materials and appropriate for this purpose (Angew. Chem. Int. Ed.- 2013, 52, 1235). After calcination, 2D CPs can be transformed into nanoporous metal oxides with a highly accessible surface area. Here, this strategy is adopted in order to form 2D nanoporous nickel oxide (NiO) with tunable porosity and crystallinity, using trisodium citrate dihydrate as a controlling agent. The presence of trisodium citrate dihydrate plays a key role in the formation of 2D nanoflakes by controlling the nucleation rate and the crystal growth. The size of the nanoflakes gradually increases by augmenting the amount of trisodium citrate dihydrate in the reaction. After heating the as-prepared CPs in air at different temperatures, nanoporous NiO can be obtained. During this thermal treatment, organic units (carbon and nitrogen) are completely removed and only the metal content remains to take part in the formation of nanoporous NiO. In the case of large-sized 2D CP nanoflakes, the original 2D flake-shapes are almost retained, even after thermal treatment at low temperature, but they are completely destroyed at high temperature because of further crystallization in the framework. Nanoporous NiO with high surface area shows significant efficiency and interesting results for supercapacitor application.