Ammonium Nickel Phosphate Research Articles

Mechano-chemical hydrothermal synthesis of NH4NiPO4·H2O and its transformation to LiNiPO4

Powder preparation of materials that can be used in production cathodes can be simplified by development of mechanical synthesis. In this paper, we report a novel approach using mechano-chemical hydrothermal synthesis of NH4NiPO4·H2O (Ammonium Nickel Phosphate Hydrate – ANP) was investigated. This method is easily scalable and is characterized with great repeatability. It uses inexpensive raw materials: NH4H2PO4 and NiCO3·Ni(OH)2·4H2O for one step synthesis without external source of heating. Reaction between substrates was conducted in water environment by planetary ball milling. As a result of high attrition inside milling chamber, both temperature and pressure is rising. By modification of conditions morphology of obtained powders can be modified. The produced ANP powders with phase purity up to 94.3 vol% (XRD measurement), were transformed to LiNiPO4 (Lithium Nickel Phosphate - LNP) by mixing with finely grinded Li2CO3 and calcination at 500 °C for 2 h. It resulted in LNP content of up to 91.2 vol% in final samples (XRD measurement). The mechano-chemical hydrothermal method was proved to be successful in terms of obtaining LNP using a dissolution – precipitation mechanism during wet milling at room temperature.

Enhanced electrochemical performance: Synergetic effect of time-dependent synthesis and redox additive concentration on ammonium nickel phosphate hydrate

Transition metal phosphates (TMP) have emerged as compelling candidates for supercapacitors because of their exceptional structural, chemical, and electrochemical properties. For the enhancement of energy density (Ed) of TMP, the use of redox-additive (RA) electrolytes is a cutting-edge trend because of the tuning between the electrode and electrolyte, which is much simpler than the fabrication of complex electrodes. Ammonium nickel phosphate hydrate powders (ANPh's) have been prepared via the hydrothermal method with varying reaction times (3, 6, and 9 h) at the constant reaction temperature of 180°C. The formation of ANPh's has been confirmed by structural and compositional analysis. The morphological analysis revealed the microplate-like architecture of ANPh's. The specific capacitance (Cs) of the optimized ANPh_6 electrode (EANPh_6) in KOH electrolyte observed 496 F g−1 with an Ed of 11.03 Wh kg−1 and a power density (Pd) of 404 W kg−1 at 10 mA cm−2 with 78.79 % retention after the 5000th galvanostatic charge-discharge (GCD) cycle at 100 mA cm−2. However, to overcome the problem of poor Ed and capacitance retention in aqueous electrolytes, the electrochemical properties of EANPh_6 are studied in RA electrolytes with varying concentrations (0.010 M to 0.020M) results in enhancement in electrochemical performance by improving redox reactions at the EANPh_6 and KOH electrolyte interface. The EANPh_6 with 0.015 M potassium ferricyanide K4Fe(CN)6 boosted 3 times greater Cs 1516 F g−1 and Ed 33.70 Wh kg−1 with Pd 487 W kg−1 at 10 mA cm−2 with enhanced cyclic stability of 87.54 % over the 5000 GCD cycles at 100 mA cm−2. The symmetric aqueous state device, EANPh_6// EANPh_6, achieved Cs, Ed, and Pd of 48.51 F g−1, 1.07 Wh kg−1, and 292.68 W kg−1 at 30 mA cm−2 current density with remarkable capacitance retention of 98 % over 5000 GCD cycles at 80 mA cm−2. Finally, it is anticipated that identifying the optimized electrode with an appropriate concentration of RA will be one of the eminent techniques to boost the electrochemical properties.

Physical and electrochemical properties of ammonium nickel phosphate by hydrothermal synthesis: phase transition from nickel phosphide to ammonium nickel phosphate

Physical and electrochemical properties of ammonium nickel phosphate by hydrothermal synthesis: phase transition from nickel phosphide to ammonium nickel phosphate

Urea assistant growth of ammonium nickel phosphate (NH4NiPO4·H2O) nanorods for high-performance nonenzymatic glucose sensors

The ammonium nickel phosphate (NH4NiPO4·H2O) nanorods were achieved via a facile hydrothermal method with urea acting as both NH4+ source and molecule template. The obtained samples were characterized by XRD, SEM, TEM, and XPS, which showed typically anisotropic growth of the crystals with rod-like structures. The diameter of the NH4NiPO4·H2O nanorods is less than 50nm. The excellent glucose sensing performance was further obtained on the NH4NiPO4·H2O nanorods modified electrode, which have two corresponding linear regions of 5μM–2100μM and 2400μM–5700μM with the sensitivity of 459.4μAmM−1cm−2 and detection limit of 0.5μM (S/N=3) in the lower concentration range and the sensitivity of 250.2μAmM−1cm−2 and detection limit of 6μM (S/N=3) in the higher concentration range. Moreover, the as prepared sensor was also applied to analyze glucose concentration in serum samples, showing high possibility for real sample analysis. The highly nonenzymatic glucose sensing performance of NH4NiPO4·H2O nanorods may be due to its intrinsic layered crystal structure and rod-like morphology. The formation process of the NH4NiPO4·H2O nanorods and the corresponding glucose sensing mechanism were also discussed based on the analysis. These results could suggest that NH4NiPO4·H2O nanorods may be favorable electrochemical sensing materials for constructing non-enzymatic sensors.

Hierarchical self-assembly flower-like ammonium nickel phosphate as high-rate performance electrode material for asymmetric supercapacitors with enhanced energy density

Ammonium nickel phosphate has a large specific capacitance as an electrode material at low current density, but its capacitance decays fast at high current density, which directly affects the rate performance of supercapacitors. Herein, we demonstrate a facile route for the controllable synthesis of hierarchical self-assembly flower-like ammonium nickel phosphate as a high-rate electrode material for asymmetric supercapacitors, which is an important strategy to enhance the energy density at high power density. The flower-like structures are hierarchically assembled by a mass of rectangular sheets, which can provide fast electron transport and short ion diffusion path, thereby exhibiting excellent electrochemical performance with ultrahigh specific capacitance of 1016 F g−1 at 1.0 A g−1. More importantly, the NH4NiPO4 · H2O materials exhibit outstanding rate performance (800 F g−1 even at large current density of 30 A g−1) and superior long-term cycle life (83% of capacity retention up to 3000 cycles at 5 A g−1). Furthermore, the NH4NiPO4 · H2O//AC asymmetric supercapacitors are assembled in aqueous KOH electrolyte, and exhibit high energy density (46.2 Wh kg−1 at 160 W kg−1 and 26.7 Wh kg−1 at a large power density of 4000 W kg−1, respectively). Due to the outstanding electrochemical performance, the all-solid-state asymmetric supercapacitors are successfully constructed using these materials.

Ammonium nickel phosphate on nickel foam with a Ni3+-rich surface for ultrasensitive nonenzymatic glucose sensors

We propose a new, simple and effective strategy to enhance the electro-catalytic activity by regulating the valence states of the electro-catalyst. The proportion of Ni3+/Ni2+ on the ammonium nickel phosphate/nickel foam electrode surface was increased after H2O2 solution treatment. The kinetic analysis results showed catalytic rate constants (Kcat) of Ni3+-rich surface electrode (4.028 × 106 cm3·mol−1·s−1) is bigger than the original electrode (4.928 × 105 cm3·mol−1·s−1), suggesting higher electro-catalytic activity of Ni3+-rich surface electrode. Ni3+-rich surface electrode shows an ultra high sensitivity (11,361 µA·mM−1·cm−2) in the range of 0.001–1 mM, which is much higher than the original electrode in the same linear range. And the sensitivity of 3579.9 µA·mM−1·cm−2 of Ni3+-rich surface electrode in the range of 2–4 mM is also enhanced compared with the original electrode.

Synthesis and Electrocatalytic Activity of Ammonium Nickel Phosphate, [NH4]NiPO4·6H2O, and β-Nickel Pyrophosphate, β-Ni2P2O7: Catalysts for Electrocatalytic Decomposition of Urea.

Electrocatalytic decomposition of urea for the production of hydrogen, H2, for clean energy applications, such as in fuel cells, has several potential advantages such as reducing carbon emissions in the energy sector and environmental applications to remove urea from animal and human waste facilities. The study and development of new catalyst materials containing nickel metal, the active site for urea decomposition, is a critical aspect of research in inorganic and materials chemistry. We report the synthesis and application of [NH4]NiPO4·6H2O and β-Ni2P2O7 using in situ prepared [NH4]2HPO4. The [NH4]NiPO4·6H2O is calcined at varying temperatures and tested for electrocatalytic decomposition of urea. Our results indicate that [NH4]NiPO4·6H2O calcined at 300 °C with an amorphous crystal structure and, for the first time applied for urea electrocatalytic decomposition, had the greatest reported electroactive surface area (ESA) of 142 cm2/mg and an onset potential of 0.33 V (SCE) and was stable over a 24-h test period.

Solubility Product of Ni-Struvite, NH<sub>4</sub>NiPO<sub>4</sub>·6H<sub>2</sub>O, at 25°C

Solubility product of a sparingly soluble salt is an important parameter in both pure and applied physical chemistry such as determination of values of thermodynamic functions or environmental implications of components of the substance. This paper presents the determination of the solubility product of ammonium nickel phosphate hexahydrate (Ni-struvite) at 25°C by analysis of equilibria attained from both supersaturated and undersaturated solutions, i.e. precipitation and dissolution, respectively. Writing the dissolution process as NH4NiPO4·6H2O → NH3 + Ni2+ ++ 6 H2O, the value pKsp = 11.03 ± 0.03 is found for both precipitation and dissolution. The solubility is a little lower than that of the isomorphous Mg salt. This is to be expected from the lattice dimensions of the two phases, the crystals of Ni-struvite being slightly more compact.

Hierarchical One-Dimensional Ammonium Nickel Phosphate Microrods for High-Performance Pseudocapacitors.

High-performance electrochemical capacitors will drive the next-generation portable, flexible and wearable electronics. Unlike the conventional all-carbon supercapacitors (electric double layer capacitors, EDLC) with high power but poor energy density, pseudocapacitors capitalize the high energy density inherent to reversible redox reactions and provide a facile means to enhancing the energy ratings of supercapacitors. The high length-to-diameter ratio and anisotropic character of 1-D architecture makes them suitable for use in energy storage. For the first time, we report 1-D microrod structures (~ 36 nm width) of ammonium nickel phosphate hydrate (ANPmr) as a pseudocapacitor with high energy rating and power handling. To confirm the data, the ANPmr-based pseudocapacitor was subjected to various configurations (i.e., half-cell, symmetric, asymmetric, and flexible all-solid-state) and in each case it gave excellent values compared to any accessible literature to date. We clearly demonstrate that a flexible all-solid-state ANPmr-based pseudocapacitor achieved high areal capacitance of 66 mF cm−2 with extra-ordinary energy (21.2 mWh cm−2) and power (12.7 mW cm−2) densities. This work opens doors for a facile, robust and scalable preparation strategy for low-cost, earth-abundant electrode materials for high-performance pseudocapacitors.

Amorphous nickel pyrophosphate microstructures for high-performance flexible solid-state electrochemical energy storage devices

Abstracts Flexible solid-state electrochemical energy storage devices with amorphous nickel pyrophosphate microstructures and graphene nanosheets as positive and negative electrode materials have been successfully assembled. Amorphous nickel pyrophosphate microstructures have been synthesized by calcination of the ammonium nickel phosphate hydrate microstructures in air at 350 °C. The device achieved a maximum volumetric energy density of 0.78 mW h cm −3 which is larger than that of most of published results, and showed a long cycle life with little capacity decay even after 6000 cycles, and maintained good mechanical flexibility under a bending angle of 0–180°.

(Invited) One-Dimensional Ammonium Nickel Phosphate Nanorods for the Fabrication of High-Performance and Flexible Symmetric Pseudocapacitors

There has been a considerable research interest in the use of electrochemical capacitors (ECs), supercapacitors (i.e., all-carbon based energy storage systems) and pseudocapacitors (i.e., redox-based energy storage systems) for the development of next generation energy storage systems for portable, flexible and wearable electronics. Supercapacitors are known for their high power density, while the pseudocapacitors are known for their high energy density [1-3]. The most attractive flexible electronics are those that employ high-performance ECs, i.e., with high energy and power densities. The performance of any EC-driven technology, including flexible electronics, is solely dependent on the physicochemical properties of their electrode materials. Electrode materials with 1D and 2D nanostructures (such as the nanorods and nanosheets) maximize the super-/pseudo-capactive properties by their unique ability to permit ion propagations [4,5]. In addition, 1D nanostructures greatly address the space-confined transport phenomena thus enhance the charge accumulation and Faradaic redox reactions [4,6]. Phosphate-rich mesoporous materials (PRMM) such as NH4CoPO4.H2O and NH4NiPO4.H2O have been reported to exhibit attractive properties for pseudocapacitors. Hitherto, however, there is no report on PRMM nanowires/nanorods for pseudocapacitors. Motivated by the attractive properties of PRMM and 1D nanomaterials in supercapacitor applications, and paucity of literature on 1D PRMM nanostructures, we have explored the possibility of tuning the structure of porous ammonium nickel phosphate hydrate (NH4NiPO4.H2O) (ANP) nanorods for high-performance all-solid-state, flexible pseudocapacitors. Here, we introduce a facile one-pot strategy to synthesize various morphologies of ANP by hydro/solvothermal route in ethylene glycol (EG), water and mixed solvents of EG/water using nickel acetate and ammonium phosphate in template-free and additive-free protocols. Three different morphologies (nanorods, nanodendrites, and nanoplatelets) with different sizes were obtained based on the reaction times and types of solvents employed. In this presentation, we will prove that ANP nanorods (Figure 1a), in contrast to their nanoplatelets and nanodentdrites counterparts, exhibit excellent improvement in pseudocapacitance. As exemplified in Figure 1b, the energy and power densities of the nanorods of ANP Figure 1: (a) FESEM image of ANP nanorods and (b) Ragone plots of different nanostructures of ANP-based all-solid-state flexible symmetric pseudocapacitors obtained at different times (24, 36 and 48 h) in the presence of EG, water (W) and mixed solvents. The electrolyte used was PVA/KOH. References 1) A.T. Chidembo, K.I. Ozoemena, B. O. Agboola, V. Gupta, G.G. Wildgoose, R.G. Compton, Energy Environ. Sci.3 (2010) 228–236. 2) J. N. Lekitima, K.I. Ozoemena, C.J. Jafta, N. Kobayashi, Y. Song, D. Tong, S.W. Chen, M. Oyama, J. Mater. Chem. A, 1 (2013), 2821 – 2826. 3) C.J. Jafta, F. Nkosi, L. le Roux, M.K. Mathe, M. Kebede, K. Makgopa, Y. Song, D. Tong, M. Oyama, N. Manyala, S.W. Chen, K.I. Ozoemena, Electrochim. Acta 2013, 110, 228 – 233 4) X. Zhao, B.M Sánchez, P.J. Dobson, P.S. Grant, Nanoscale, 3,839-855 (2011). 5) X Peng, L. Peng, C. Wu, Yi Xie. Chem. Soc. Rev. 43,3303-3323 (2014). 6) Y.R. Ahna, C.R. Park, S.M. Jo, D.Y. Kim,Appl. Phys. Lett. 90, 122106 (2007). Figure 1

Mesoporous uniform ammonium nickel phosphate hydrate nanostructures as high performance electrode materials for supercapacitors

Mesoporous uniform ammonium nickel phosphate hydrate nanostructures are successfully prepared by a one-pot hydrothermal method. As a result of the unique feature of large surface area (418 m2 g−1) and tunable mesostructures, the material exhibits good performance as supercapacitor electrodes, with a specific capacitance of 1072 F g−1 in 3.0 M KOH at a current density of 1.50 A g−1, and show a good cycle life which does not obviously decay after 3000 cycles (the retention 95.0% of initial specific capacitance after 3000 cycles).

In Situ XRD, XAS, and Magnetic Susceptibility Study of the Reduction of Ammonium Nickel Phosphate NiNH4PO4·H2O into Nickel Phosphide

The reduction of the ammonium nickel phosphate NiNH(4)PO(4) x H(2)O precursor into nickel phosphide (Ni(2)P), a highly active phase in hydrotreating catalysis, was studied using a combination of magnetic susceptibility and in situ X-ray diffraction and X-ray absorption spectroscopy (XAS) techniques. The transformation of NiNH(4)PO(4) x H(2)O into Ni(2)P could be divided into three distinguishable zones: (1) from room temperature to 250 degrees C, the NiNH(4)PO(4) x H(2)O structure was essentially retained; (2) from 300 to 500 degrees C, only an amorphous phase was observed; (3) above 500 degrees C, a crystallization process occurred with the formation of Ni(2)P. An in situ XAS study and magnetic susceptibility measurements clearly revealed for the first time that the amorphous region corresponds to the nickel pyrophosphate phase alpha-Ni(2)P(2)O(7). The phosphate reduction into phosphide did not start before 550 degrees C and led to the selective formation of Ni(2)P at 650 degrees C.

X-ray powder diffraction data for ammonium nickel phosphate monohydrate

Ammonium nickel phosphate monohydrate (NH4NiPO4·H2O) crystal data were obtained by X-ray powder diffraction. Ammonium nickel phosphate monohydrate is orthorhombic with unit-cell parameters a = 5.566 (1) Å, b = 8.760 (2) Å, and c = 4.742 (1) Å.