NiO Nanostructures Research Articles

Boosted formic acid electro-oxidation on platinum nanoparticles and "mixed-valence" iron and nickel oxides.

The modification of Pt nanoparticles (nano-Pt, assembled electrochemically onto a glassy carbon (GC) substrate) with hybrid multivalent nickel (nano-NiOx) and iron (nano-FeOx) oxide nanostructures was intended to steer the mechanism of the formic acid electro-oxidation (FAO) in the desirable dehydrogenation pathway. This binary modification with inexpensive oxides succeeded in mediating the reaction mechanism of FAO by boosting reaction kinetics "electron transfer" and amending the surface geometry of the catalyst against poisoning. The sequence of deposition was optimized where the a-FeOx/NiOx/Pt/GC catalyst (where "a" denotes a post-activation step for the catalyst at -0.5 V in 0.5 mol L-1 NaOH) reserved the best hierarchy. Morphologically, while nano-Pt appeared to be spherical (ca. 100 nm in average diameter), nano-NiOx appeared as flowered nanoaggregates (ca. 56 nm in average diameter) and nano-FeOx (after activation) retained a plate-like nanostructure (ca. 38 nm in average diameter and 167 nm in average length). This a-FeOx/NiOx/Pt/GC catalyst demonstrated a remarkable catalytic efficiency (125 mA mgPt-1) for FAO that was ca. 12.5 times that of the pristine Pt/GC catalyst with up to five times improvement in the catalytic tolerance against poisoning and up to -214 mV shift in the FAO's onset potential. Evidences for equipping the a-FeOx/NiOx/Pt/GC catalyst with the least charge transfer resistance and the highest stability among the whole investigated catalysts are provided and discussed.

Hollow nanostructured NiO particles as an efficient electrode material for lithium-ion energy storage properties.

This work has developed a straightforward approach to obtaining NiO hollow structures by using Li2O2 as an easily removable template. The easy availability and electrochemically active nature of NiO have attracted researchers' attention as an anode electrode for Li-ion storage applications, including Li-ion secondary batteries (LIBs) and for Li-ion hybrid supercapacitors (LiHSCs; which offer higher power densities than LIBs without compromising energy density). However, NiO usage has been limited to its low reaction reversibility, poor conductivity, and conversion reaction capability. Recently, hollow nanostructured materials have attracted attention as efficient battery materials due to their fascinating structural features. This study presents a modified Li2O2-assisted method to obtain porous open 3D architectures of NiO nanostructures. The resultant hollow structures are electrochemically studied as an anode for a LIB, exhibiting excellent stability over hundreds of cycles. The result is recognized as one of the finest among NiO anodes reported. Also, NiO hollow structures studied as anodes for LiHSC devices fabricated with activated carbon cathodes exhibit an outstanding comprehensive electrochemical performance which is better than the typical LIB and supercapacitors.

Effect of precursor concentration on stoichiometry and optical properties of spray pyrolyzed nanostructured NiO thin films

In this study, spray pyrolysis was used to produce nanostructured NiO thin films from high purity nickel acetate (Ni(CH3COO)2.3H2O) precursors on pre-heated ultrasonically cleaned soda-lime glass substrates. The metallic constituent concentrations in the films were varied, and the precursors were produced in distilled water at various molarities ranging from 0.1 to 0.4 M. In the study, the field-emission scanning electron microscope (FESEM) results strongly confirmed adherence of the films to the glass substrate at 350 °C. The presence of Ni and O in the samples was confirmed using Rutherford backscattering spectroscopy (RBS), X-ray diffractometry (XRD) and energy dispersive X-ray spectroscopy (EDX). For the 0.1 M NiO thin films, the thickness was approximately 43 nm, and for the 0.2 M, 0.3 M, and 0.4 M films, the thickness was 46 nm, 47 nm, and 49 nm, respectively. The XRD findings were supported by the increased Raman intensity peaks with increased precursor concentration, which confirmed the films' improved crystallinity. For the same number of passes of films deposition, as the molar concentration increases, the films thickness increases. The amount of nickel in NiO thin films increases as the molarity increases, but the amount of oxygen in NiO thin films decreases as the molarity increases. It was discovered that as molarity increases, the optical transmittance decreases and the optical band gap narrows. The qualities of NiO discovered in this study suggest the films’ potentials for usage as window layer and buffer material in thin film solar cells.

Synthesis, characterization, electrochemical and catalytic performance of NiO nanostructures and Ag-NiO nanocomposite

Nanocomposites comprising oxide and metal nanoparticles could significantly boost respective functionalities attributing to their synergistic properties. Present work reports synthesis of NiO and its composite; Ag-NiO nanocomposite. The study highlights electrochemical and catalytic performances of synthesized materials. The X-ray diffraction pattern, X-ray photoelectron spectra, magnetic and morphological study is presented with detailed analysis. Transmission electron microscopy images showed Ag nanoparticles distributed within NiO nanostructures. The cyclic voltammetry results showed specific capacitance of 231 F/g for Ag-NiO nanocomposite; higher than bare NiO (90 F/g) at 5 mV/s scan rate in 1 M KOH electrolyte. Moreover, the Ag-NiO nanocomposite exhibited significant catalytic activity towards methylene blue reduction with rate constant 1.1 × 10−2s−1. The study covers basic analysis of NiO and Ag-NiO nanocomposite extending towards their functional performance.

Electrochemical deposition of NiO bunsenite nanostructures with different morphologies as the hole transport layer in polymer solar cells

• Electrodeposition of p-type nickel oxide (NiO) using anodic potentiostatic and cyclic voltammetry. • Applying both NiO as the hole transport layer (HTL) in the fabrication of polymer solar cells. • NiO synthesized by the anodic potentiostatic exhibited the best features as the HTL. • The best PSC showed J SC , V OC , FF , and PCE of 10.95 mA/cm 2 , 0.64 V, 0.60 and 4.21%, respectively. Hole transport layers (HTLs) are one of the most important components of bulk heterojunction polymer solar cells (BHJ PSCs), having functions of optimizing interface, adjusting the energy match, and helping obtain higher PCE. Inorganic p-type semiconductors are alternative HTLs due to their chemical stability, high mobility, high transparency, and applicable valence band (VB) energy level. In this work, interlayer engineering in BHJ PSC was performed using solution-processed p-type nickel oxide (NiO) as the HTL. NiO nanostructures were synthesized by anodic potentiostatic and cyclic voltammetry (CV) electrodeposition methods. Simple adjustment of the applied potential regime and electrodeposition parameters led to considerable structural and electrochemical changes in the resulting NiO. Eventually, the best sample was selected in terms of suitable surface conductivity, high optical transparency, and appropriate energy levels. NiO nanostructures with FCC crystal structure synthesized by anodic potentiostatic electrodeposition showed conductivity of 0.038 mS.cm -1 and charge mobility of 2.01 cm 2 .V -1 s -1 , respectively, about 30.2% and 24.8% higher than the NiO synthesized by CV. The anodic potentiostatic electrodeposition method increased the photovoltaic performance of the PSCs by 43% compared to the CV method. The average power conversion efficiencies for the anodic potentiostatic and CV methods were 2.95% and 4.21%, respectively. The PCE of these cells was about 13% and 62% higher than that considered for the reference device prepared based on the PEDOT:PSS HTL.

Green Synthesis of NiO-SnO2 Nanocomposite and Effect of Calcination Temperature on Its Physicochemical Properties: Impact on the Photocatalytic Degradation of Methyl Orange

Background: Nickel stannate nanocomposites could be useful for removing organic and toxic water pollutants, such as methyl orange (MO). Aim: The synthesis of a nickel oxide-tin oxide nanocomposite (NiO-SnO2 NC) via a facile and economically viable approach using a leaf extract from Ficus elastica for the photocatalytic degradation of MO. Methods: The phase composition, crystallinity, and purity were examined by X-ray diffraction (XRD). The particles' morphology was studied using scanning electron microscopy (SEM). The elemental analysis and colored mapping were carried out via energy dispersive X-ray (EDX). The functional groups were identified by Fourier transform infrared spectroscopy (FTIR). UV-visible diffuse reflectance spectroscopy (UV-vis DRS) was used to study the optical properties such as the absorption edges and energy band gap, an important feature of semiconductors to determine photocatalytic applications. The photocatalytic activity of the NiO-SnO2 NC was evaluated by monitoring the degradation of MO in aqueous solution under irradiation with full light spectrum. The effects of calcination temperature, pH, initial MO concentration, and catalyst dose were all assessed to understand and optimize the physicochemical and photocatalytic properties of NiO-SnO2 NC. Results: NiO-SnO2 NC was successfully synthesized via a biological route using F. elastica leaf extract. XRD showed rhombohedral NiO and tetragonal SnO2 nanostructures and the amorphous nature of NiO-SnO2 NC. Its degree of crystallinity, crystallite size, and stability increased with increased calcination temperature. SEM depicted significant morphological changes with elevating calcination temperatures, which are attributed to the phase conversion from amorphous to crystalline. The elemental analysis and colored mapping show the formation of highly pure NiO-SnO2 NC. FTIR revealed a decrease in OH, and the ratio of oxygen vacancies at the surface of the NC can be explained by a loss of its hydrophilicity at increased temperatures. All the NC samples displayed significant absorption in the visible region, and a blue shift is seen and the energy band gap decreases when increasing the calcination temperatures due to the dehydration and formation of compacted large particles. NiO-SnO2 NC degrades MO, and the photocatalytic performance decreased with increasing calcination temperature due to an increase in the crystallite size of the NC. The optimal conditions for the efficient NC-mediated photocatalysis of MO are 100 °C, 20 mg catalyst, 50 ppm MO, and pH 6. Conclusions: The auspicious performance of the NiO-SnO2 NCs may open a new avenue for the development of semiconducting p-n heterojunction catalysts as promising structures for removing undesirable organic pollutants from the environment.

Graphitic-C3N4/chitosan-doped NiO nanostructure to treat the polluted water and their bactericidal with in silico molecular docking analysis

Different concentrations (2 and 4 wt%) of graphite carbon nitride (g-C3N4) was doped into fixed amount of chitosan (CS) and nickel oxide (NiO) nanoparticles (NPs) via a co-precipitation route. The aim of study is to remove the pollutants from wastewater through catalytic activity (CA) and determine the bactericidal activities of synthesized products. X-ray diffraction pattern confirmed the cubic structure of NiO NPs and peak shifted to higher angle upon g-C3N4 doping. Fourier transform infrared spectroscopy revealed the existence of bending and stretching vibration mode. The absorption decreased gradually accompanied blue-shift and assessed bandgap energy increased upon doping. The high resolution transmission electron microscopy micrographs confirmed the formation of cubic-shaped NPs and elongated nanorods were seen for NiO and co-doped NiO. The catalytic efficiency of samples was examined using methylene blue (MB) in the presence of reducing agent. A remarkable dye de-colorization was confirmed with a g-C3N4 and CS doping; moreover, the bactericidal efficacy compared to Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was observed as 3.15 and 13.8 mm, respectively. In silico, molecular docking investigations targeting against b-lactamaseS. aureus and FabHE. coli enzymes assisted to elaborate the mechanism underlying microbicidal action of the NPs.

Effect of Rotational Speed on the Structural, Morphological, and Optical Properties of Biosynthesized Nickel Oxide Thin Films for Selective Solar Absorber Nanocoatings

This article presents a simple and low-cost green synthesized single-layer NiO selective solar absorber nanocoating prepared by spin coating on a Cu substrate at different rotational speeds (RS). The effects of substrate RS on the structural, morphological, chemical, and optical properties of the NiO nanocoatings were thoroughly investigated. The XRD results reveal the formation of pure diffraction peaks indexed to face-centered cubic NiO nanocoatings. SEM confirmed the uniform distribution of the NiO thin films with a nanosphere-like structure and the influence of RS variation on the formation of NiO nanostructures. EDS and XPS confirmed the presence of Ni and O in the green synthesized NiO coatings. AFM showed homogeneous nanopillar-like NiO thin films with the average surface roughness decreasing from 13.6 to 9.06 nm as the RS increased from 700 to 1300 RPM. Raman spectroscopy of the nanocoatings showed normal modes related to longitudinal optical and transverse optical phonons, and a combination of both, which implies the presence of a defect-rich or anti-ferromagnetically ordered NiO film responsible for the occurrence of more scattering peaks. UV–Vis–NIR and Fourier transform infrared spectroscopy (FTIR) were employed to characterize the optical properties of the nanocoatings. The green synthesized NiO nanocoatings deposited at 700 RPM exhibited excellent solar absorptance (α) of 0.92 and low thermal emittance (ɛ) of 0.11. The optical properties of the selective materials obtained in the present work were correlated with the non-stoichiometric nature of the spin-coated sample, multiple reflections, and interference-induced light absorption on the green synthesized surface. These results suggest that the NiO thin films prepared through this simple and environmentally benign green synthesis method can be promising candidates for efficient solar selective absorbers.

A facile surfactant-assisted precipitation route to self-assembled 3D flower-shaped NiO nanostructures with enhanced surface area

A facile surfactant-assisted precipitation route to self-assembled 3D flower-shaped NiO nanostructures with enhanced surface area

Role of surface defects in the third order nonlinear optical properties of pristine NiO and Cr doped NiO nanostructures

Pristine NiO and 2% Cr doped NiO nanostructures are successfully synthesized by the modified auto–combustion method for the determination and improvement of linear and nonlinear optical behaviours, and for identifying them as suitable materials for optical limiting applications. Vibrational and linear optical properties of both nanostructures are investigated, and structural and morphological studies are carried out using XRD, FE-SEM, and HR-TEM. From the Kubelka-Munk model, the energy band gaps for pristine and doped samples are found to be 3.52 eV and 3.44 eV, respectively. Both pristine as well as Cr-doped NiO nanostructures reveal substantial nonlinear optical behaviour at the excitation wavelength of 532 nm, arising from the presence of strong reverse saturable absorption. The third order nonlinear absorption coefficients have values of the order of 10−10 m/W and 10−6 m/W, under pulsed (5 ns) and continuous wave laser excitations, respectively. These values confirm the suitability of these nanostructures for fabricating efficient optical limiting devices for safeguarding human eyes and optical sensors from hazardous laser radiation.

Hydrothermally synthesised nickel oxide nanostructures on nickel foam and nickel foil for supercapacitor application

Nickle-based oxides exhibit seamless redox activity and show undisputed parameter optimization flexibility, which makes them a candidate of choice for various scientific analysis and multipurpose execution. The communique addresses the domain of energy storage of hydrothermally fabricated nickel oxide nanostructures by analysing the capacitive behaviour of the sample. The crystal geometry, chemical composition and bonding state of the material were carried out through XRD and XPS analysis, respectively. Electron microscopy showed systematically aligned nano-needles, which in aggregate represent an urchin. A comparative study of specific capacitance (Cs) at a scan rate of 1 mVs−1 showed an enhanced Cs of nickel oxide embedded Ni-foam (1125 Fg-1) against nickel oxide deposited Ni-foil (454 Fg-1). At a current density of 8 mAcm −2, the nickel oxide based Ni-foam electrode exhibited an energy density of 23 Whkg−1 and a power density of 259 Wkg-1 which makes it instrumental in electrochemical devices. The Ni-foam electrode also showed less ‘cycle fatigue’ as its charge/discharge stability dipped by just 12% even after 5000 cycles. The novel supercapacitor electrode developed in this study exhibits excellent specific capacitance, high stability, high power density, and low impedance, demonstrating its promising practical functionality.

Unique Decoration of NiO Nanostructures on the Electrospun Carbon Nanofibers for High Performance Supercapacitor

Carbon materials having fibrous structures and large specific surface area have shown the great utility value as an electrode material and catalyst support because they present excellent chemical stability, good ionic fluidity and electrical conductivity. Recently, the combination of carbon nanofibers (CNFs) and transition metal oxides such as NiO are received a great deal of interest as effective electrode materials for high performance electrochemical. In the present work, NiO decorated CNFs materials were prepared by the hydrothermal growth of NiO on the surface of electrospun CNFs at low temperature. For CNFs preparation, the electrospinning method was adopted by using 10% PAN solution with the electrospinning conditions like stock feeding rate of 0.5 ml/h and supplying a constant voltage of 15 kV. The obtained PAN mat was first under gone by stabilization at 280oC for 2h and then performed the carbonization in a tube furnace under N2 atmosphere at 800°C for 2 h. The prepared electrospun CNFs and decorated NiO/CNFs were extensively analyzed by various experimental tools such as FE-SEM, TEM, XRD, FTIR and Raman analysis. The structural and crystalline observations deduced the significant and uniform decoration of NiO nanostructures on electrospun CNFs. The decorated NiO/CNFs were applied as electrode for fabricating the electrochemical supercapacitor by measuring cyclicvoltametry (CV) and galvanostatic charge/discharge (GCD). The decorated NiO/CNFs electrode attained the good specific capacitance with excellent rate capability in 1M Na2SO4 solution as electrolyte. Therefore, the decorated NiO/CNFs would be highly promising material for high performance supercapacitors.

Synthesis of self-grown nanostructured NiO via pulse ionization for binderless psuedocapacitor electrode

In air laser irradiation was carried out onto Ni sheet with ultra-short, pulsed laser for direct synthesis of NiO thin layer. The layer consisted of 3D nanostructures with excellent porosity and enhanced surface area for the fabrication of pseudo capacitive electrodes. Mainly laser parameters such as scan speed and frequency were analyzed. It was observed that at lower scan speed, excellent surface area was achievable which during microscopy, the morphology of the structure depicted a “broccoli” like structure. The oxidized layer forms because of series of events at ultra-short duration associated with laser-material interaction in ambient conditions such as energy transfer, heating, melting, evaporation, ionization, plasma formation, rapid quenching, and oxide layer formation. The obtained oxide layer consists of 3D self-standing nanostructure with the active material directly growing on the substrate without the requirement of binder. A combined contribution of pseudo capacitance due to surface rapid, redox reactions along with ion adsorption-desorption because of EDL's presence provided remarkable performance. With this fabrication approach, NiO, a battery active material demonstrated fast charge-discharge capabilities evident from galvanostatic charge-discharge test. Owing to the idea of one step direct synthesis and green fabrication process, the performance of the electrode was remarkable. An areal capacitance of 98.682 mF cm−2 and specific capacity of 59.209 mC cm−2 was achievable at a current density of 1 mA cm−2. This work promotes the idea of green synthesis of nano morphology and one step fabrication method.

Experimental investigations on morphology controlled bifunctional NiO nano-electrocatalysts for oxygen and hydrogen evolution

Developing a single electrocatalyst effective for both oxygen and hydrogen evolution remains challenging. Although an attempt to utilize a single electrocatalyst for overall water splitting is made, there still exist several issues of efficiency and stability of the electrocatalyst. Hence, the present study reports on morphology-controlled NiO electrocatalyst, a single electrocatalyst for oxygen and hydrogen evolution. The cubic phase NiO nanoparticles and nanoplates of diameter and thickness <10 nm delivered surface-to-volume ratios of 0.078 and 0.083, respectively. XRD and TEM confirm the formation of NiO nanostructures, where morphology transformed independently of the chemical composition. XPS and EXAFS confirm the 2+ oxidation state of Ni ions and its octahedral coordination with oxygen. The 0D nanoparticles providing a larger surface area and active sites offered the overpotentials of 373 and 268 mV for OER and HER activity, respectively, and performed well than the 2D porous NiO nanoplates. The chronoamperometry and repetitive LSV cyclic studies confirmed the excellent long-term stability of 0D NiO nanoparticles in basic and acidic mediums during electrocatalytic water splitting reactions, owing to its increased electrochemically exposed active sites.

Enhanced electrochemical performance of facilely synthesized cobalt doped cubic NiO nanoflakes for supercapacitor application

Being inexpensive, nontoxic and environmental friendly, NiO has caught special attention as a promising electrode material for supercapacitors. We recently reported facile synthesis of porous NiO nanocrystallites for energy storage application. A sophisticated strategy to improve the electrochemical properties of NiO which is a p-type semiconductor is the incorporation of 3d metal ions into it. In this article, we present successful fabrication of highly porous cobalt doped NiO nanostructures through a facile, low cost, one step solution combustion method without a post calcination treatment and demonstrate the influence of cobalt content on structural properties and electrochemical behavior. The thus prepared Co doped NiO samples were systematically characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Field emission scanning electron microscopy, High resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller measurements, cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. It was found that the phase structure of pristine NiO remains unaffected by the process of doping. But doping obviously influences the textural and morphological properties, more importantly, enhances the electrochemical properties of pristine NiO. A maximum specific capacity of 746 C/g (specific capacitance of 1244 F/g) was obtained for an optimum cobalt dopant ratio, which is superior to undoped NiO (295 C/g). Moreover, cobalt doped NiO nanostructures exhibited a good rate capability (71 % capacity retention from 1 to 15 A/g) and long term cycling stability (83.7 % after 5000 cycles at 100 mV/s). An asymmetric device fabricated using Co doped NiO electrode as the positive electrode and activated carbon as the negative electrode delivered an energy density of 32.7 Wh/kg at a power density of 261 W/kg.

Two-dimensional NiO nanosheets for efficient Congo red adsorption removal

Strategies for developing new adsorbents are necessary for more efficient processes to remove contaminants from wastewater. Thus, it is essential to adjust the synthesis parameters of the adsorbent nanomaterial to control the surface area and morphology and, therefore, enhance the adsorption performance. Herein, α-Ni(OH)2 nanosheets were synthesized via a simple and fast microwave-assisted solvothermal method and converted to NiO nanostructures by calcination in air. The effect of different calcination temperatures (range of 300–600 °C) on the morphology, crystal structure, and adsorption performance of Congo red (CR) was evaluated. The calcination of α-Ni(OH)2 at 300 °C resulted in 2D NiO nanosheets, which showed the best performance to remove CR dye due to the increased surface area and porosity provided by the 2D morphology. The nanosheet-like structure is lost with increasing the calcination temperature and the nanoparticles become bigger, consequently, the CR adsorption capacities are significantly reduced. The 2D NiO nanosheets can adsorb a significant amount of CR quickly, reaching equilibrium after only 120 min, indicating a high affinity between the adsorbate species and the surface of the adsorbent. Additionally, the adsorption isotherm was compatible with the Langmuir model, which provides a maximum calculated adsorption capacity of 259.74 mg g−1. Thus, our findings showed how to adequate the synthesis parameters to obtain NiO nanosheets and improve the adsorption parameters to CR, which can be extended to the fabrication of new materials to promote advances in sustainable technologies.

Facile synthesis and characterization of metal ions (Ce, Cu, Gd, Mn and Y) doped Nickel Oxide nanostructures for spintronic and photodiode applications

Multiphase hexagon and flower-shaped structures of NiO nanocomposites have been prepared with different metal ions (Ce, Cu, Gd, Mn and Y) using facile and low-cost co-precipitation method. The optical, structural, morphological, and magnetic properties of the synthesized nanostructures have been investigated. The XDR measurement reveals the coexistence of several crystal structures like cubic, monoclinic, tetragonal, and orthorhombic which unveils the formation of polymorphism in the nanocomposites with high crystallinity. A wideband has been located in the FT-IR spectra at around 600 cm−1 revealing the metal oxide (M-O) phase formation. DRS exhibits four large and intense absorption bands at 260, 380, 420, and 720 nm in the UV and visible domains assigned to the nanocrystalline phases of NiO, CuO, CeO, and MnO, respectively. SEM images of metal-doped nickel oxide nanocomposites show a white sponge, semi-spherical, flower-like, and hexagon-shaped particles of 15 nm size. TEM result establishes a smooth surface for samples grown from gadolinium and yttrium, contrary to other samples made off cerium and manganese demonstrate a rough surface. A ferromagnetic tendency has been located for samples prepared from copper, manganese, and gadolinium-based NiO nanocomposites with coercivities of 132, 113, and 26 Oe, correspondingly. Photodiode characteristics were also investigated on the developed devices. These outcomes signify their use in spintronic and optoelectronic industries.

A symmetry-based approach to the characterization of complex surface morphologies: Application in CuO and NiO nanostructures

In recent years, bottom-up nanofabrication techniques and especially solution-based ones have gained significant popularity due to their relatively facile implementation, low-cost and design flexibility that allows the development of a plethora of three-dimensional nanostructures and nanoarchitectures. Nonetheless, despite the apparent simplicity of the methods, the resulting nanostructures are often morphologically and hierarchically complex with no apparent way of appropriately describing their features in a quantifiable and methodological way. In this work, we propose a symmetry-based approach for the quantitative characterization of the morphology of nanostructured surfaces. The key idea is to characterize the morphology of nanostructures by means of the fundamental spatial symmetry metrics and the deviations from the fully symmetrical counterparts. The focus of the proposed methodology is on the translational and scaling symmetry, which are investigated through the mathematical tools of Fourier and (multi)fractal analysis, respectively. The calculated metrics characterizing these symmetries are the period and the fractal dimension of surfaces while the deviations are quantified by the disorder parameter ω d related to the FWHM of Fourier peak and by the asymmetry of the multifractal spectrum for the translational and scaling symmetry respectively. As an initial study case and in order to demonstrate its suitability, the developed symmetry-based methodology was applied to nickel oxide (NiO) and copper oxide (CuO) nanostructures hydrothermally-grown on silicon substrates. The results show that even in the cases where the surfaces display similar symmetry metrics (period, fractal dimension) the symmetry-based approach reveals subtle, but quantifiable differences in the deviations from full symmetries which are not easily identified by other approaches. • A symmetry-based method for nanometrological analysis of complex nanomorphologies is developed and implemented. • It detects and quantifies the spatial symmetries in surfaces and the deviations from these (surface disorder). • Fourier, correlation and (multi) fractal analysis are used. • The method is successfully applied in CuO and NiO nanostructures hydrothermally grown on silicon substrates. • It captures subtle differences in nanosurface translational and scaling disorder and evaluates material/process origins.

Surfactant-assisted facile synthesis of petal-nanoparticle interconnected nanoflower like NiO nanostructure for supercapacitor electrodes material

Nickel oxide (NiO) nanostructures with diverse morphology were prepared by facile sol–gel route using cationic, anionic, and non-ionic surfactants as stabilizing agents. The effects of surfactants on the physical and morphological properties of NiO were investigated. In addition, the electrochemical properties of grown products were also studied. We have observed that cationic surfactant (CTAB) leads to petal-nanoparticle interconnected nanoflower-like morphology. The electrochemical study revealed that all electrodes have pseudocapacitive nature with Faradic charge-storage mechanism. The CTAB assisted electrode owns large specific capacitance/energy density/power density of 397F/g/27.57 Wh/kg/0.54 KW/kg at 1 A/g current density in 1.0 M KOH electrolyte with superior cycling stability. The formation of nanoflower-like morphology in CTAB assisted electrode provides a larger surface area for ions transportation, higher conductivity, fast charge transfer, higher current density, and high electrochemical active surface area, attributing to boosted supercapacitive behavior of synthesized electrodes.

NiO/nitrogen-oxygen co-doped carbon nanoflower composites based on covalent organic frameworks for lithium-ion battery anodes

Designing novel NiO/porous carbon nanocomposites is an effective strategy to improve poor conductivity and rapid capacity fading of NiO in lithium-ion batteries (LIBs). Covalent organic frameworks (COFs) are attractive materials for LIBs as they have large specific surface areas, well-ordered structure, and controllable pore size. Here, we designed a COFTpPa nanoflower as templates for the preparation of porous carbon and a carrier for NiO to obtain NiO/nitrogen-oxygen co-doped carbon nanoflower (NiO/NCF) composites. NiO nanostructures have a smaller volume effect, and the coating of carbon nanoflowers can further buffer the volume expansion of NiO nanostructures, which effectively slow down the capacity decay. In addition, the NCF derived from COFTpPa provide a larger specific surface area and more pores, which not only increases the capacity of nanocomposites but also improves the electrical conductivity of the electrodes. When applied to the anode of LIBs, NCF and NiO/NCF exhibit excellent performance (with first-cycle capacities of 1038.2 and 1685.9 mAh g−1, respectively, and high first coulomb efficiencies of 61.5 % and 60.9 %, respectively). The designed NiO/NCF nanocomposites is a promising anode material for LIBs.