Accurate estimation of Li/Ni mixing degree of lithium nickel oxide cathode materials

Li/Ni mixing negatively influences the discharge capacity of lithium nickel oxide and high-nickel ternary cathode materials.However,accurately measuring the Li/Ni mixing degree is difficult due to the preferred orientation of labbased XRD measurements using Bragg–Brentano geometry.Here,we find that employing spherical harmonics in Rietveld refinement to eliminate the preferred orientation can significantly decrease the measurement error of the Li/Ni mixing ratio.The Li/Ni mixing ratio obtained from Rietveld refinement with spherical harmonics shows a strong correlation with discharge capacity,which means the electrochemical capacity of lithium nickel oxide and high-nickel ternary cathode can be estimated by the Li/Ni mixing degree.Our findings provide a simple and accurate method to estimate the Li/Ni mixing degree,which is valuable to the structural analysis and screening of the synthesis conditions of lithium nickel oxide and high-nickel ternary cathode materials.

Tuned d-band states over lanthanum doped nickel oxide for efficient oxygen evolution reaction

The d-band state of materials is an important descriptor for activity of oxygen evolution reaction(OER).For NiO materials,there is rarely concern about tuning their d-band states to tailor the OER behaviors.Herein,NiO nanocrystals with doping small amount of La^(3+)were used to regulate d-band states for promoting OER activity.Density of states calculations based on density functional theory revealed that La^(3+)doping produced upper shift of d-band center,which would induce stronger electronic interaction between surface Ni atoms and species of oxygen evolution reaction intermediates.Further density functional theory calculation illustrated that La^(3+)doped NiO possessed reduced Gibbs free energy in adsorbing species of OER intermediate.Predicted by theoretical calculations,trace La^(3+)was introduced into crystal lattice of NiO nanoparticles.The La^(3+)doped NiO nanocrystal showed much promoted OER activity than corresponding pristine NiO product.Further electrochemical analysis revealed that La^(3+)doping into NiO increased the intrinsic activity such as improved active sites and reduced charge transfer resistance.The in-situ Raman spectra suggested that NiO phase in La^(3+)doped NiO could be better maintained than pristine NiO during the OER.This work provides an effective strategy to tune the d-band center of NiO for efficient electrocatalytic OER.

Synthesis, Characterization, and Effects of Morphology on the Magnetic Application Base Properties of Pure Nickel Oxide (NiO) and Cobalt-Doped Nickel Oxide/Nickel Hydroxide (CoxNi1-xO/Ni(OH)2) Nanocomposites

Nano particle (NP) morphology is one of the material properties at the origin of potential application base properties exploited in several engineering and technology domains, such as fuel cell, electrodes, catalysis, sensing, electric, thermal, magnetic, and photovoltaic applications. The general properties and particle morphology of nickel oxide/Nickel hydroxide NPs can be modified by the introduction of impurity atoms or ions. Nano sized nickel oxide/nickel hydroxide nanocomposites were obtained from the thermal decomposition of single molecular precursors synthesized by a modified oxalate route using Carambola fruit juice as a precipitating agent. The compositional and morphological variations were studied by introducing cobalt as an impurity ion at different w/w% fractions (0%, 0.1%, 0.3%, 0.5%, 1%, 3%, 5.0%, 40.0% and 50.0%) into the microstructure of the nickel oxide/hydroxide. The precursors were characterized by FT-IR, while TGA/DTG analysis was carried out to decompose the precursors. The precursors decomposed at 400°C and were characterized by PXRD and SEM/TEM. The results revealed that Pure Nickel Oxide (NiO) and, Cobalt-doped Nickel Oxide/nickel hydroxide (CoxNi1-xO/Ni(OH)2) Nano composites have been synthesized and the synthesized samples have exhibited three distinct morphologies (porous face-centered cubic nano rods, rough and discontinuous CoxNi1-xO/Ni(OH)2) composite and, smooth and continuous mix spherical/cuboidal mixed morphological phase of (NiO/CoO). The morphology of the NPs varied with the introduction of the dopant atoms and with increase in the concentration of dopant atoms in the composite. Magnetic studies using vibrating sample magnetometry revealed superparamagnetic properties which correlated strongly with particle size, shape and morphology. Observed values of retention (4.50 × 10-3 emu/g) and coercivity (65.321 Oe) were found for 0.5 w/w% corresponding to impregnated porous nanorods of Co-doped NiO, and retention (9.03 × 10-3 emu/g) and coercivity (64.341 Oe), for X = 50.0%, corresponding to an aggregate network of a Nano spherical/cubic CoO/NiO mixed phase. Magnetic properties within this range are known to improve the magnetic memory and hardness of the magnetic materials. Therefore, the synthesized Cobalt-doped Nickel Oxide/nickel hydroxide (CoxNi1-xO/Ni(OH)2) Nano composites have potential applications in Magnetic memories and hardness of magnetic materials.

Synthesis, Characterization, and Effects of Morphology on the Magnetic Application Base Properties of Pure Nickel Oxide (NiO) and Cobalt-Doped Nickel Oxide/Nickel Hydroxide (CoxNi1-xO/Ni(OH)2) Nanocomposites

Nano particle (NP) morphology is one of the material properties at the origin of potential application base properties exploited in several engineering and technology domains, such as fuel cell, electrodes, catalysis, sensing, electric, thermal, magnetic, and photovoltaic applications. The general properties and particle morphology of nickel oxide/Nickel hydroxide NPs can be modified by the introduction of impurity atoms or ions. Nano sized nickel oxide/nickel hydroxide nanocomposites were obtained from the thermal decomposition of single molecular precursors synthesized by a modified oxalate route using Carambola fruit juice as a precipitating agent. The compositional and morphological variations were studied by introducing cobalt as an impurity ion at different w/w% fractions (0%, 0.1%, 0.3%, 0.5%, 1%, 3%, 5.0%, 40.0% and 50.0%) into the microstructure of the nickel oxide/hydroxide. The precursors were characterized by FT-IR, while TGA/DTG analysis was carried out to decompose the precursors. The precursors decomposed at 400°C and were characterized by PXRD and SEM/TEM. The results revealed that Pure Nickel Oxide (NiO) and, Cobalt-doped Nickel Oxide/nickel hydroxide (CoxNi1-xO/Ni(OH)2) Nano composites have been synthesized and the synthesized samples have exhibited three distinct morphologies (porous face-centered cubic nano rods, rough and discontinuous CoxNi1-xO/Ni(OH)2) composite and, smooth and continuous mix spherical/cuboidal mixed morphological phase of (NiO/CoO). The morphology of the NPs varied with the introduction of the dopant atoms and with increase in the concentration of dopant atoms in the composite. Magnetic studies using vibrating sample magnetometry revealed superparamagnetic properties which correlated strongly with particle size, shape and morphology. Observed values of retention (4.50 × 10-3 emu/g) and coercivity (65.321 Oe) were found for 0.5 w/w% corresponding to impregnated porous nanorods of Co-doped NiO, and retention (9.03 × 10-3 emu/g) and coercivity (64.341 Oe), for X = 50.0%, corresponding to an aggregate network of a Nano spherical/cubic CoO/NiO mixed phase. Magnetic properties within this range are known to improve the magnetic memory and hardness of the magnetic materials. Therefore, the synthesized Cobalt-doped Nickel Oxide/nickel hydroxide (CoxNi1-xO/Ni(OH)2) Nano composites have potential applications in Magnetic memories and hardness of magnetic materials.

Coral-Like Yolk–Shell-Structured Nickel Oxide/Carbon Composite Microspheres for High-Performance Li-Ion Storage Anodes

In this study, coral?like yolk–shell?structured NiO/C composite microspheres(denoted as CYS?NiO/C) were prepared using spray pyrolysis. The unique yolk–shell structure was characterized, and the formation mechanism of the structure was proposed. Both the phase separation of the polyvinylpyrrolidone and polystyrene(PS) colloidal solution and the decompo?sition of the size?controlled PS nanobeads in the droplet played crucial roles in the formation of the unique coral?like yolk–shell structure. The CYS?NiO/C microspheres delivered a reversible discharge capacity of 991 mAh g^(-1) after 500 cycles at the current density of 1.0 A g^(-1). The dis?charge capacity of the CYS?NiO/C microspheres after the 1000 th cycle at the current density of 2.0 A g^(-1) was 635 mAh g^(-1), and the capacity retention measured from the second cycle was 91%. The final discharge capacities of the CYS?NiO/C microspheres at the current densities of 0.5, 1.5, 3.0, 5.0, 7.0, and 10.0 A g^(-1) were 753, 648, 560, 490, 440, and 389 mAh g^(-1), respectively. The synergetic e ect of the coral?like yolk–shell structure with well?defined interconnected mesopores and highly conductive carbon resulted in the excellent Li+?ion storage properties of the CYS?NiO/C microspheres.

Nickel oxide for inverted structure perovskite solar cells

The emergence of inverted perovskite solar cells(PSCs) has attached great attention derived from the potential in improving stability. Charge transporting layer, especially hole transporting layer is crucial for efficient inverted PSCs. Organic materials were used as hole transporting layer previously. Recently, more and more inorganic hole transporting materials have been deployed for further improving the device stability. Nickel oxide(NiOx) as p-type metal oxide, owning high charge mobility and intrinsic stability,has been widely adopted in inverted PSCs. High performance over 20% efficiency has been achieved on NiOx base inverted PSCs. Herein, we have summarized recent progresses and strategies on the NiOx based PSCs, including the synthesis or deposition methods of NiOx, doping and surface modification of NiOx for efficient and stable PSCs. Finally, we will discuss current challenges of utilizing NiOx HTLs in PSCs and attempt to give probable solutions to make further development in efficient as well as stable NiOx based PSCs.

The role of nickel oxide additive in lowering the carbon dioxide sorption temperature of CaO

A new type of calcium-based regenerable carbon dioxide （CO_2） sorbent, CaO-NiO, was synthesized via the sol-gel method. The as synthesized CO_2 sorbent was in the form of nanoparticles. The CO_2 sorption temperature and capacity of the sorbent were examined using thermogravi- metric analysis （TGA）. The CaO-NiO sorbent is able to capture CO_2 at a lower sorption temperature （465 ℃） than pure calcium oxide （CaO） （600 ℃）. The role of NiO in the CaO-NiO sorbent in lowering the CO_2 sorption temperature was also investigated. The sorbent was char- acterized by X-ray diffractometer （XRD）, N_2 adsorption-desorption analysis, high resolution transmission electron microscopy （HRTEM） and scanning electron microscopy （SEM）. CaO and NiO were found to coexist in the sorbent. Neither solid solution nor mixed metal oxide was formed. NiO did not react with CO_2 in the sorption process; but it worked like a catalyst to promote the CaO carbonation reaction. It is suggested that this new CaO-NiO sorbent may have a promising application as an effective CO_2 sorbent with lower energy consumption.

Preparation of Lanthanum Nickel Oxide-Coated Ni Sheet Anodes and Their Application to Electrolytic Production of (CF_3)_3N in (CH_3)_4NF·4.0HF Melt

A new process for electrolytic production of a perfluorinated compound, （CF3）3N, using lanthanum nickel oxide-coated Ni sheet anode in the （CH3）4NF· 4.0HF melt at room temperature, was developed. Thin films of the lanthanum nickel oxides were prepared on Ni sheets by sol-gel coating method using polyvinlylpyrrolidone（PVP）. The main components of the thin films were La2O3, LaNiO3, and La2NiO4 at 500, 750 and 1000℃, respectively. The anode performance in the （CH3）4NF·4.0HF melt depends greatly on the main component of the thin film, and the LaNiO3-coated Ni sheet anode gives the best anode performance. The potential of LaNiO3-coated Ni sheet anode remains constant at 5.9 V during electrolysis at 20 mA·cm^-2 in the （CH3）4NF·4.0HF melt for 100 h. This is because LaNiO3 and NiF3 and/or Ni2F5, the latter of which was formed during electrolysis, in the film give a high electronic conductivity to the surface film during electrolysis. The maximum mole fraction of （CF3）3N （21.4%） was obtained at 20 mA·cm^-2 in （CH3）4NF·4.0HF melt using the LaNiO3-coated Ni sheet.

Nanosized Nickel Oxides Derived from the Citrate Gel Process and Performances for Electrochemical Capacitors

Nanosized nickel oxide powders were prepared by thermal decomposition of the nickel citrate gel precursors. The thermal decomposition and powder materials derived from calcination of these gel precursors with various ratios of citric acid （CA） to nickel at different temperatures and times were characterized by thermal analysis （TG/DTA）, scanning electron microscopy （SEM）, x-ray diffraction （XRD）, and measurement of specific surface area （BET） with porosity analyses. The optimized processing conditions of calcination temperature 400℃ for 1 hour with the CA/Ni ratio of 1.2, were determined to produce the nanosized nickel oxide pow- ders with a high specific surface area of 181 m^2/g, nanometer particle sizes of 15-25 nm, micro-pore diameter distribution between 4-10 nm. The capacitance characteristics of the nanosized nickel oxide electrode in various concentrations of KOH solutions were studied by the cyclic voltammetry （CV） exhibiting both a double-layer capacitance and a faradaic pseudocapacitance. The nanosized nickel oxide electrode shows a high cyclic stability and is promising for high performance electrochemical capacitors.

Performance of a combined capacitor based on ultrafine nickel oxide/carbon nanotubes composite electrodes

A new sol-gel process for the preparation of ultrafine nickel hydroxideelectrode materials was developed. The composite electrodes consisting of carbon nanotubes andNi(OH)_2 were developed by mixing the hydroxide and carbon nanotubes together in different massratios. In order to enhance energy density, a combined type pseudocapacitor/electric double layercapacitor was considered and its electrochemical properties were characterized by cyclic voltammetryand dc charge/discharge test. The combined capacitor shows excellent capacitor behavior with anoperating voltage up to 1.6 V in KOH aqueous electrolyte. Stable charge/discharge behaviors wereobserved with much higher specific capacitance values of 24 F/g compared with that of EDLC (12 F/g)by introducing 60 percent Ni(0H)_2 in the anode material. By using the modified anode of aNi(OH)_2/carbon nanotubes composite electrode, the specific capacitance of the cell was lesssensitive to discharge current density compared with that of the capacitor employing pure nickelhydroxide as anode. The combined capacitor in this study exhibits high energy density and stablepower characteristics.

Effect of nickel oxide morphology on the nitrogen electrochemical reduction reaction

In order to study the effect of catalysts’morphology on the electrochemical reduction of nitrogen gas,sample catalysts of NiO with four different morphologies(hollow spherical,sea urchin-shape,cubic block,and rod-like)were prepared.Characterization of the NiO catalysts was carried out using SEM,BET,XRD and electrochemical investigation techniques.The results indicated that the nitrogen reduction reaction(NRR)is strictly dependent on the morphology of the NiO catalysts,as the hollow spherical NiO showed the best electrochemical NRR performance of NH3 yield rate(3.21μg h^-1 mg^-1 cat.,4.1910^-11 mol cm^-2 s^-1)and Faradaic efficiency(1.37%),which was higher than the yields and efficiencies of the rod-NiO(1.8μg h^-1 mg^-1 cat.,3.2410^-11 mol cm^-2 s^-1,1.17%),sea urchin-NiO(1.66μg h^-1 mg^-1 cat.,2.4410^-11 mol cm^-2 s^-1,1.08%)and cubic block-NiO(1.32μg h^-1 mg^-1 cat.,2.1410^-11 mol cm^-2 s^-1,0.81%),respectively.These results match the order of the specific surface area of the NiO samples,with hollow spherical(113.91 m^2 g^-1)>rod-NiO(55.12 m^2 g^-1)sea urchin-NiO(55.29 m^2 g^-1)>cubic block-NiO(38.57 m^2 g^-1).This correlation can be attributed to the fact that large specific surface areas can provide more active sites for electrocatalysis.This work demonstrates the effect of the morphology of the NiO catalysts on its electrochemical NRR properties,which could offer some opportunity for the preparation of new electrode materials with improved electrocatalytic properties.

Electrochemical performance of nickel oxide/KOH/active carbon super-capacitor

The fabrication and characterization of new type Nickel oxide/KOH/Activecarbon super-capacitor have been described. Porous nickel oxide was prepared by hydrolysis of nickelacetate and heated in air at 300 deg C. The resulting nickel oxide behaved as an electrochemicalcapacitor electrode with a specific capacitance (50-70 F/g) superior to most active carbonelectrodes. This kind of nickel oxide maintained high utilization at high rate of discharge (i.e.,high power density) and had excellent cycle life more than 1000 times, while the capacitance of thecell composed of two identical nickel oxide electrodes was poor at high discharge current densityand the maximum operational voltage of this type capacitor was limited to 0.5 V. A new typesuper-capacitor was designed in which the nickel oxide and the active carbon were applied to thepositive and negative electrodes respectively. The breakdown voltage of this type super-capacitorwas improved effectively to 0.8 V and excellent characteristic of high power discharge was attainedin this way. The Nickel oxide/KOH/Active carbon super-capacitor has promising potentials in portabletelecommunications, uninterruptable power supplies and battery load leveling applications.

Investigation of Nickel Oxide Used for Alloying in BOF Steelmaking

Direct alloying of nickel oxide in a hot simulator of LD converter was investigated in laboratory.Reduction rate of nickel oxide in steelmaking process was analyzed with the test results. Under the condition oflower slag viscosity, the reduction rate of NiO increases and the [Ni] yield rises. When the slag viscosity is higher, a lot of metal particles with higher Ni content are contained in the slag so as to decrease the [Ni] yield.

Dye Regeneration Kinetics of Sensitized Nickel Oxide Films under Illumination Investigated by Scanning Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) feedback mode has been used to investigate regeneration kinetics on P1 (4-(bis-{4-[5-(2,2-dicyanovinyl) thiophene-2-yl] pH-enyl} amino) benzoic acid) dye sensitized nickel oxide (NiO) electrodes in contact with reduced iodide liquid electrolyte in different electrolyte solvents. We were used acetonitrile, ethanol, methanol and propylene carbonate solvents for comparison under illumination of different wavelengths. We found significant variation of regeneration kinetics parameters such as regeneration rate constant (keff), the reduction rate constant (kred) and absorption cross-section (Φhv) in different illumination intensity and different solvents.

Non-Enzymatic Glucose Sensor Based on the Novel Flower Like Morphology of Nickel Oxide

In this study, novel nickel oxide (NiO) flowers like nanostructures were fabricated onto gold coated glass substrate by hydrothermal method using high alkaline pH medium. The structural study of nickel oxide nanostructures was performed by scanning electron microscopy (SEM) and X-ray differaction (XRD) techniques. Nickel oxide nanostructures are highly dense, uniform and possess good crystalline quality. The so prepared structures were investigated for their electrochemical properties by cyclic voltammetry and amperometric techniques. The nickel oxide flower like morphology has shown good electrochemical performances for the oxidation of glucose. The presented sensing material was able to detected glucose in a wide range of concentration of 0.001 mM to 8 mM with a high sensitivity (123 μmA/mM) and regression coefficient of 0.99. Moreover, the NiO nanostructures based sensor is highly reproducible, stable, exhibiting a fast response time and selective in the response. All the obtained results indicate the potential use of this material in the development of enzyme free sensors for the detection of glucose.

A novel silver-doped nickel oxide hole-selective contact for crystalline silicon heterojunction solar cells

Based on its band alignment,p-type nickel oxide(NiO_(x))is an excellent candidate material for hole transport layers in crystalline silicon heterojunction solar cells,as it has a smallΔEV and largeΔEC with crystalline silicon.Herein,to overcome the poor hole selectivity of stoichiometric NiO_(x) due to its low carrier concentration and conductivity,silver-doped nickel oxide(NiO_(x):Ag)hole transport layers with high carrier concentrations were prepared by co-sputtering high-purity silver sheets and pure NiO_(x) targets.The improved electrical conductivity of NiO_(x) was attributed to the holes generated by the Ag^(+)substituents for Ni^(2+),and moreover,the introduction of Ag^(+)also increased the amount of Ni^(3+)present,both of which increased the carrier concentration in NiO_(x).Ag^(+)doping also reduced the c-Si/NiO_(x) contact resistivity and improved the hole-selective contact with NiO_(x).Furthermore,the problems of particle clusters and interfacial defects on the surfaces of NiO_(x):Ag films were solved by UV-ozone oxidation and high-temperature annealing,which facilitated separation and transport of carriers at the c-Si/NiO_(x) interface.The constructed c-Si/NiO_(x):Ag solar cell exhibited an increase in open-circuit voltage from 490 to 596 mV and achieved a conversion efficiency of 14.4%.

Salt-assisted vapor-liquid-solid growth of high-quality ultrathin nickel oxide flakes for artificial synapses in image recognition applications

Transition metal oxides have attracted intense interest owing to their abundant physical and chemical properties.The controlled preparation of large-area,high-quality two-dimensional crystals is essential for revealing their inherent properties and realizing high-performance devices.However,fabricating two-dimensional(2D)transition metal oxides using a general approach still presents substantial challenges.Herein,we successfully achieve highly crystalline nickel oxide(NiO)flakes with a thickness as thin as 3.3 nm through the salt-assisted vapor-liquid-solid(VLS)growth method,which demonstrated exceptional stability under ambient conditions.To explore the great potential of the NiO crystal in this work,an artificial synapse based on the NiO-flake resistive switching(RS)layer is investigated.Short-term and long-term synaptic behaviors are obtained with external stimuli.The artificial synaptic performance provides the foundation of the neuromorphic application,including handwriting number recognition based on artificial neuron network(ANN)and the virtually unsupervised learning capability based on generative adversarial network(GAN).This pioneering work not only paves new paths for the synthesis of 2D oxides in the future but also demonstrates the substantial potential of oxides in the field of neuromorphic computing.

Change of Electrical and Transport Properties of Nickel Oxide by Carrier Concentration and Temperature through First‑Principle Calculations

Nickel is typically used as one of the main components in electrical contact devices or connectors.Nickel oxide(NiO)is usually formed on the surfaces of electrodes and can negatively impact system performance by introducing electrical contact resistance.The thermal,electrical,and transport properties of NiO,as a Mott insulator or a p-type semiconductor,can be altered by operating and environmental conditions such as temperature and stress/strain by contact.In this study,we inves-tigate the fundamental material properties of NiO through the first-principle calculations.First,we obtain and compare the lattice parameter,magnetic moment,and electronic structure for NiO via the WIEN2K simulations with four different poten-tials(i.e.,GGA,GGA+U,LSDA,and LSDA+U).Then,using the WIEN2K simulation results with LSDA+U potential that produces a highly accurate bandgap for NiO,we calculate the electrical conductivity and electrical part of the thermal conductivity of nickel and NiO as a function of temperature and carrier concentration through the BoltzTraP simulations.Systematic simulation results revealed that the electrical conductivity relative to the relaxation time for NiO increases with the carrier concentration,while it shows a slightly decreasing trend with temperature under a fixed carrier concentration.By contrast,the electrical part of the thermal conductivity shows an increasing trend considering carrier concentration and temperature.