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.

Preparation of ammonium jarosite from clinker digestion solution of nickel oxide ore roasted using(NH_4 )_2SO_4

To obtain the appropriate conditions for eliminating Fe3＋from NiSO4 solution, the digestion solution of the clinker was used as raw material, which was obtained from roasting the nickel oxide ore with （NH4）2SO4. The ammonium jarosite was successfully synthesized from the solution with analytic grade NH4HCO3. The effects of reaction temperature, reaction time, end pH value of reaction on the removal rate of iron were investigated, and the effect of the initial concentration of Fe3＋was also discussed. All of those factors had significant effects on the removal rate of Fe3＋, among which the reaction temperature was the most prominent. The appropriate reaction conditions were concluded as follows： reaction temperature 95 ℃ reaction time 3.5 h, end pH value of reaction 2.5 at initial concentration of Fe3＋19.36 g/L. The physical aspect of （NH4）2Fe6（SO4）4（OH）12 was cluster figure composed of sheet or prismatic particles with smooth surface.

Nickel Oxide/Carbon Nanotubes Nanocomposite for Electrochemical Capacitance

A nanocomposite of nickel oxide/carbon nanotubes was prepared through a simple chemical precipitation followed by thermal annealing. The electrochemical capacitance of this electrode material was studied. When the mass fraction of CNTs (carbon nanotubes) in NiO/CNT composites increases, the electrical resistivity of nanocomposites decreases and becomes similar to that of pure CNTs when it reaches 30%. The specific surface area of composites increases with increasing CNT mass fraction and the specific capacitance reaches 160 F/g under 10 mA/g discharge current density at CNT mass fraction of 10%.

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.

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 as an Electrode Material for Supercapacitors

The preparation of Ni oxide films and their capacitive mechanism are discussed in this paper. Nickel oxide film electrodes perform pseudocapacitance in aqueous KOH and NaOH but perform double layer capacitance in LiCIO4/PC (propylence carbonate). The effect of increasing the specific capacitance was observed when Ni oxide film electrodes are doped with Co. A specific capacitance of around 70 F/g was achieved when using Ni oxide films doped with Co as electrodes and 1 mol/L aqueous KOH or NaOH as an electrolyte.

Tuning catalytic selectivity of propane oxidative dehydrogenation via surface polymeric phosphate modification on nickel oxide nanoparticles

Thermal stability has long been recognized as a major limitation for the application of ligand modification in high-temperature reactions. Herein, we demonstrate polymeric phosphate as an efficient and stable ligand to tune the selectivity of propane oxidative dehydrogenation. Beneficial from the weakened affinity of propene, NiO modified with polymeric phosphate shows a selectivity 2–3 times higher than NiO towards the production of propene. The success of this regulation verifies the feasibility of ligand modification in high-temperature gas-phase reactions and shines a light on its applications in other important industrial reactions.

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.

Electrocatalytic water oxidation by a nickel oxide film derived from a molecular precursor

In this study,we fabricated a NiOx film by electrodeposition of an ethanediamine nickel complex precursor(pH=11)on a fluorine‐doped tin oxide substrate.The resulting film is robust and exhibits high catalytic activity for electrochemical water oxidation.Water oxidation is initiated with an overpotential of375mV(1mA/cm2)and a steady current density of8.5mA/cm2is maintained for at least10h at1.3V versus the normal hydrogen electrode.Kinetic analysis reveals that there is a2e?/3H+pre‐equilibrium process before the chemical rate‐determining step.The low‐cost preparation,robustness,and longevity make this catalyst competitive for applications in solar energy conversion and storage.

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.

Boosting ethanol oxidation over nickel oxide through construction of quasi-one-dimensional morphology and hierarchically porous structure

Quasi-one-dimensional NiO with a hierarchically porous structure was synthesized through a facile coordination−precipitation method with the coupling effect of ammonia and a post-calcination treatment.The electrocatalytic properties of NiO fibers for the oxidation of ethanol were compared with those of NiO spheres.The results show that the fibrous NiO possesses a larger specific surface area of 140.153 m2/g and a lower electrical resistivity of 4.5×105Ω·m,leading to an impressively superior electrocatalytic activity to spherical NiO for ethanol oxidation in alkaline media.The current decay on fibrous NiO at 0.6 V in 100−900 s was 0.00003%,which is much lower than that of spherical NiO,indicating its better stability.The unique morphology and hierarchically porous structure give the fibrous NiO great potential to be used as an anodic electrocatalyst for direct ethanol fuel cells.

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.