Nickel Molybdate Research Articles

Electrochemical and electrical properties of nickel molybdate / carbon material composites

The aim of this paper is to establish the optimal content of carbon material in composites with nanocrystal hydrate nickel molybdate. To achieve this, NiMoO4 / C composites with a carbon material content of 1, 5 and 10% by weight (with and without ultrasonic irradiation) were obtained by hydrothermal method. As a result of electrochemical studies, it was found that the maximum specific capacitance of 628 F/g is reached by a composite with a carbon content of 1% after ultrasonic exposure, while this composite shows excellent electrical conductivity, which is 0.47 Ohm-1m-1.

A simplified fabrication of α-NiMoO4 via greener approach: Properties and its photocatalytic activity

The research work demonstrates the facile fabrication of nickel molybdates (NiMoO4) nanocatalyst via greener approach using moringa oleifera extract as chelating agent. The phase and crystalline structure, functional groups, morphology were characterized using characterization tools. The XRD patterns confirms the monoclinic phase structure of α-NiMoO4 with the crystallite size of ~18 nm. The existence of Ni 2p, Mo 3d and O1s energy levels characteristics in the synthesized nanocatlayst was determined from the XPS analysis. Then the prepared nanocatalyst (α-NiMoO4) used as active material to degrade the methylene blue (effluent dye) under visible light and solar radiation. The photo-degradation efficiency of MB achieved to be 91% over the optimal nanocatalyst (NiMoO4) under solar radiation condition over 2 h and 81% for visible light under the same condition. Pseudo first order reaction rate constants of NiMoO4 for both visible light and solar light irradiation are determined to be 0.01387 min−1 and 0.01902 min−1, respectively.

Porous, 3D-hierarchical α-NiMoO4 rectangular nanosheets for selective conductometric ethanol gas sensors

Transition metal oxides with unique nanoarchitectures are being appraised as plausible candidates for the highly selective detection of contaminating organic gases due to their earth abundance, high surface area, and outstanding miniaturization potential. Here, two different nanoarchitectures of nickel molybdate (NMO), namely 3D-honeycombs (NMO-HCs) and 3D-rectangular nanosheets (NMO-RNS), are proposed and synthesized via a two-step wet-chemical process and characterized for their potential application in ethanol gas sensors. The successful formation of the different nanostructures and the even distribution of all the elements are demonstrated using various morphological and energy-dispersive X-ray spectroscopic (EDAX) analyses. In addition, N2-adsorption/desorption analysis is performed to confirm the highly porous nature and maximum surface areas of 30.4 m2 g−1 and 91.3 m2 g−1 at 77 K for the NMO-HCs and NMO-RNS, respectively. Furthermore, gas sensing analysis reveals that the NMO-HCs-based sensor provides a maximum gas response (Ra/Rg) of ~15.2 while the NMO-RNS-based sensor exhibits a 5.5 times higher maximum gas response of ~78.9 at the optimal operating temperature. Further, using Ra/Rg = 1.2 as the detection limit point, the lower limit of ethanol gas detection is found to be 0.2 ppm for the NMO-RNS-based device. Finally, the probable gas-sensing mechanism of the NMO-RNS is discussed. The present study indicates that the NMO-RNS sensor can sense ppb-levels of ethanol and is suitable for the monitoring of outdoor and indoor air quality in practical applications.

Synergistic effects of nanoarchitecture and oxygen vacancy in nickel molybdate hollow sphere towards a high‐performance hybrid supercapacitor

The facile design and fabrication of nanoarchitectured binary transition metal oxide electrode materials are essentially required for the advancement of high-performance supercapacitors (SCs). Herein, we prepared an oxygen-vacant NiMoO4 (Ov-NiMoO4) hollow sphere via a simple hydrothermal approach and subsequent heat treatment under an argon atmosphere. In particular, the oxygen vacancy is confirmed by using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Raman, and differential reflectance spectroscopy (DRS) UV-Vis spectra studies. Furthermore, the generation of the oxygen vacancy could enhance the electrical conductivity and improve Faradaic redox sites. Significantly, the Ov-NiMoO4 hollow sphere depicts a larger specific capacity (Csp) of 496 mA h g−1 at 1 A g−1 than the bare-NiMoO4 (b-NiMoO4; 279 mA h g−1) thermally treated under air. Furthermore, the hybrid SC (HSC) is fabricated based on the Ov-NiMoO4//activated carbon, revealing a high specific capacitance (Cs) of 120 F g−1 and providing a large energy density (ED) of 37.49 W h kg−1 and power density (PD) of 36.61 kW kg−1. Moreover, the HSC shows considerable cyclic stability of ~91.14% over 20 000 cycles. The results divulge that the poor crystallinity and the introduction of oxygen vacancies play a vital role in enhancing the charge-storage capability of the materials.

Synthesis of transition metal cation decorated nickel molybdate nanoarrays on nickel foam and their applications in high-performance battery-supercapacitor hybrid devices

Molybdenum-based metal oxides have attracted enormous attention because of their high specific capacity, but they still cannot meet current needs. To further enhance the electrochemical performance of the electrodes, we synthesized nanostructured zinc (Zn-)-decorated and cobalt (Co-)-decorated NiMoO4 arrays directly on nickel foams through a simple hydrothermal reaction followed by a calcination procedure. After being decorated with the transition metal cations, the capacities of the hybrid electrodes were marginally superior to the pristine NiMoO4. The optimized Co-decorated NiMoO4 electrode (CNM2) and Zn-decorated electrode (ZNM2) could deliver a high capacity of 1257.3 C g−1 and 969.2 C g−1, respectively, at a current density of 10 mA cm−2. The as-assembled CNM2//activated carbon battery-supercapacitor hybrid device yielded a high capacity of 87.4 F g−1 at a current density of 5 mA cm−2, maximum energy density of 31.1 W h kg−1 at the power density of 1249.9 W kg−1 and excellent stability with capacitance retention of 91.1% after 5000 continuous cycles at a current density of 10 mA cm−2. This work provides an alternative to fabricate other cation decorated transition metal oxide electrodes via a facile synthesis strategy and enable potential applications in the energy storage fields.

Heterogeneous photocatalytic degradation of organic pollutant in aqueous solutions by S-scheme heterojunction in nickel molybdate nanocomposites

A novel ɑ-NiMoO4/ɑ-MoO3 binary nanocomposite was fabricated by using facile method. The fabricated nanocomposite was characterized by various techniques, and the photocatalytic activity was evaluated in degradation of Acid blue 92 dye. Among of as-made photocatalysts with various weight ratios of ɑ-MoO3, ɑ-NiMoO4/ɑ-MoO3 (1:5%w/w) exhibited the best photocatalytic performance, and selected as optimum photocatalyst. Under optimum reaction conditions ([dye] = 10 mg L−1, [catalyst] = 200 mg L−1, and pH = 7.0), complete removal efficiency was obtained within 100 min. Also, the first-order rate constant value of reaction in the presence of ɑ-NiMoO4/ɑ-MoO3 was calculated to be 0.032 min−1 that was 3.05, and 2.13 times higher than ɑ-NiMoO4 and ɑ-MoO3, respectively. The improvement photocatalytic performance of ɑ-NiMoO4/ɑ-MoO3 is depended to efficient separation of charge carries, which confirmed by EIS, and PC analysis. According to the radical trapping experiments, hydroxyl radical (HO•), and photo-generated holes (h+) were the dominant reactive species in this reaction. In addition, the recycling experiments indicated that, ɑ-NiMoO4/ɑ-MoO3 nanocomposite has remarkable stability without losing the activity after four consecutive photocatalytic runs. The present study reports a new method for the synthesis of Mo-based nanocomposite for the environmental applications.

Electrochemical tuning of nickel molybdate nanorod arrays towards promoted electrocatalytic urea oxidization

Urea electrolysis enables simultaneous energy-saving hydrogen production and wastewater purification at a small thermodynamic potential of 0.37 V; however, the total energy-utilization efficiency is still substantially restricted by the sluggish kinetics of the urea oxidization reaction (UOR) at the anode. In this work, an electrochemical tuning strategy has been employed to obtain a Ni (III)-enriched catalyst by starting from NiMoO4∙xH2O nanorod arrays. It has been found that the electrochemical tuning not only modifies the valency state of Ni but also causes a dramatic change in stoichiometry and microstructure of the material, leading to significantly improved activities for UOR under alkaline conditions. Notably, the obtained catalyst delivers a current density of 100 mA cm−2 for UOR at the potential of only 1.36 V vs RHE, which surpasses the best-reported values for UOR catalysis at the same applied potential, demonstrating the great promise of the electrochemical tuning strategy in rational modifications of material towards promoted electrocatalysis.

Raman spectroscopy of nickel molybdate and its modifications

While using hydrothermal method we obtained nanocrystal nickel molybdate hydrate (NiMoO4). Its further calcination at 400 °C enabled us to obtain α-phase of NiMoO4 hydrate. The modification of physical and chemical properties of prepared NiMoO4 hydrate was being done with the aid of powerful laser radiation with the further composite formation on its basis. We have established the interconnection of vibrational modes of triclinic and monoclinic structures of nickel molybdates with corresponding bands in Raman spectra. We established that registered intensive bands with maximum 947, 870, 828, and 354 cm−1 correspond to vibrational modes of МоО4 tetrahedrons of NiMoO4 hydrates, while intensive bands with maximum 960, 912, and 706 cm−1 in α-NiMoO4 correspond to stretching vibrational modes in Мo–О and О–Мo–О, bending modes О–Мo–О connections in MoO6 octahedron.

Synthesis and Electrochemical Properties of Nanocrystalline Nickel Molybdate

We have obtained nanocrystalline hydrate and alpha phase of nickel molybdate by a hydrothermal technique. On the basis of the obtained cyclic voltammetry data, we have evaluated the contribution of faradaic and non-faradaic processes to the total capacitance of molybdates under study. It was found that the specific capacitance of hydrate NiMoO4·H2O is 621 F/g at a scan rate of 1 mV / s and the specific capacitance of the α-NiMoO4 is 281 F/g. Cathodes for hybrid supercapacitors were formed on the basis of the obtained nickel molybdates. As a result of electrochemical studies, it was found that the specific capacitance of hybrid supercapacitor based on NiMoO4·H2O/C was 256 F/g at the current of 0.2 A/g, while the specific energy was 80 W h/kg and specific power – 304 W/kg and these results are higher below in the α-NiMoO4 /C-based hybrid supercapacitor.

Highly Efficient Methylene Blue Dye Removal by Nickel Molybdate Nanosorbent.

Removing methylene blue (MB) dye from aqueous solutions was examined by the use of nickel molybdate (α-NiMoO4) as an adsorbent produced by an uncomplicated, rapid, and cost-effective method. Different results were produced by varying different parameters such as the pH, the adsorbent dose, the temperature, the contact time, and the initial dye concentration. Adsorbent dose and pH had a major removal effect on MB. Interestingly, a lower amount of adsorbent dose caused greater MB removal. The amount of removal gained was efficient and reached a 99% level with an initial methylene blue solution concentration of ≤160 ppm at pH 11. The kinetic studies indicated that the pseudo-second-order kinetic model relates very well with that of the obtained experimental results. The thermodynamic studies showed that removing the MB dye was favorable, spontaneous, and endothermic. Impressively, the highest quantity of removal amount of MB dye was 16,863 mg/g, as shown by the Langmuir model. The thermal regeneration tests revealed that the efficiency of removing MB (11,608 mg/g) was retained following three continuous rounds of recycled adsorbents. Adsorption of MB onto α-NiMoO4 nanoparticles and its regeneration were confirmed by Fourier transform infrared spectroscopy (FTIR) analysis and scanning electron microscopy (SEM) analysis. The results indicated that α-NiMoO4 nanosorbent is an outstanding and strong candidate that can be used for removing the maximum capacity of MB dye in wastewater.

High performance flexible energy storage device based on copper foam supported NiMoO4 nanosheets-CNTs-CuO nanowires composites with core–shell holey nanostructure

Because of the intensified electrochemical activities, mixed metal oxides as a representative for pseudocapacitive materials play a key role for high performance supercapacitor electrodes. Nevertheless, low ion and electron transfer rate and poor cycling performance in the electrode practically restrict further promotion of their electrochemical performance. In order to offset the defect, a novel copper (Cu) foam-supported nickel molybdate nanosheet decorated carbon nanotube wrapped copper oxide nanowire array (NiMoO4 NSs-CNTs-CuO NWAs/Cu foam) flexible electrode is constructed. The as-prepared electrode demonstrates a unique core-shell holey nanostructure with a large active surface area, which can provide a large number of active sites for redox reactions. Besides, the CNTs networks supply improved conductivity, which can hasten electron transport. Through this simple and efficient design method, the spatial distribution of each component in the flexible electrode is more orderly, short and fast electron transport path with low intrinsic resistance. As a result, the NiMoO4 NSs-CNTs-CuO NWAs/Cu foam as an adhesiveless supercapacitor electrode material exhibits excellent energy storage performance with high specific areal capacitance of 23.40 F cm−2 at a current density of 2 mA cm−2, which outperforms most of the flexible electrodes reported recently. The assembled asymmetric supercapacitor demonstrates an energy density up to 96.40 mW h cm-3 and a power density up to 0.4 W cm-3 under a working voltage window of 1.7 V. In addition, outstanding flexibility of up to 100° bend and good cycling stability with the capacitance retention of 82.53 % after 10,000 cycles can be obtained.

Methods of obtaining nickel molybdates and composites of molybdate/carbon material for electrodes of hybrid supercapacitors (Review)

Nickel molybdate due to its electronic configuration, stable crystalline framework, oxidation-reduction behavior displays perfect physical and chemical properties and rather high electrical conductivity that altogether lets the material display high total capacity. The research work classified modern methods of obtaining nickel molybdates and composites with carbon material on their basis. We have analyzed the fundamental stages of hydrothermal, microwave synthesis, ultrasonic dispersion, mechano-chemical, sol-gel method, and chemical precipitation method. The influence of different synthesis conditions on phase structure, morphology, physical and electrochemical properties of material was displayed.

Tuning the electronic structure of NiMoO4 by coupling with SnO2 for high-performance hybrid supercapacitors

Nickel molybdate (NiMoO4) has been regarded as a promising battery-type electrode material for hybrid supercapacitors (HSCs) because of its low cost, high theoretical capacity and richer redox reactions. However, its large-scale application is limited by the poor rate performance and low stability. In this work, we suggest that the electronic structure tuning can effectively improve the capacity but also enhance the stability. Such tuning can be readily realized by coupling NiMoO4 with SnO2. The introduction of SnO2 promotes the electron transfer from NiMoO4 to SnO2 and therefore reduces the electron density of NiMoO4, which leads to an enhanced adsorption of OH− ions and thus boosts the capacity. As a result, the SnO2@NiMoO4/CP core-shell electrode exhibits a high capacity of 0.65 mA h cm−2 (257.8 mAh g−1) at a current density of 5 mA cm−2 (2 mA g−1) along with greatly enhanced stability. Besides, the assembled HSC device using SnO2@NiMoO4/CP as cathode and active carbon/CP as anode shows a superior specific capacity of 109.5 mAh g−1 at 5 mA cm−2 and excellent cycling performance with a capacity retention of 92.2% at 50 mA cm−2, as well as a high specific energy of 78.4 Wh kg−1 at a power density of 895 W kg−1, outperforming many other reported hybrid supercapacitors.

Influence of Nickel molybdate nanocatalyst for enhancing biohydrogen production in microbial electrolysis cell utilizing sugar industrial effluent

Biohydrogen production in Microbial Electrolysis Cell (MEC) had inspired the researchers to overcome the challenges associated towards sustainability. Despite microbial community and various substrates, economical cathode catalyst development is most significant factor for enhancing hydrogen production in the MEC. Hence, in this study, the performance of MEC was investigated with a sugar industry effluent (COD 4200 ± 20 mg/L) with graphite anode and modified Nickel foam (NF) cathode. Nickel molybdate (NiMoO4) coated NF achieved a higher hydrogen production rate 0.12 ± 0.01 L.L−1D−1 as compared to control under favorable conditions. Electrochemical characterizations demonstrated that the improved catalytic activity of novel nanocatalyst with lower impedance favoring faster hydrogen evolution kinetics. The MEC with the novel catalyst performed with 58.2% coloumbic efficiency, 20.36% cathodic hydrogen recovery, 11.96% overall hydrogen recovery and 54.38% COD removal efficiency for a 250 mL substrate during 5 days’ batch cycle. Hence, the potentiality of modified cathode was established with the real time industrial effluent highlighting the waste to wealth bio-electrochemical technology.

Novel electrochemical sensor based on modified glassy carbon electrode with graphene quantum dots, chitosan and nickel molybdate nanocomposites for diazinon and optimal design by the Taguchi method

In this study, a new sensitive and selective electrochemical sensor was offered based on the modification of activated glassy carbon electrode (GCEox) with graphene quantum dots, chitosan, and nickel molybdate (NiMoO4) nanocomposites for diazinon determination. A simple method of fabricating a sensor was presented based on covalent immobilization of polymer and nanoparticle due to functional groups on the GCEox surface. The surface of the constructed sensor was characterized by field-emission scanning electron microscopy (FE-SEM) and electrochemical impedance spectroscopy (EIS). Optimal factors of experiments have been evaluated and analyzed using Minitab software by the Taguchi method (TM). Under optimized conditions, the constructed sensor illustrated two linear ranges between 0.1 and 330 μM and a limit of detection (LOD) of 30 nM using differential pulse voltammetry methods. Analytical parameters were determined, and the results were compared with similarly reported data. The proposed sensor display reasonable stability, good reproducibility, selectivity to the detection of the diazinon. The effect of interferences was studied on the sensor's function, accompanied by the recovery analysis of diazinon in cucumber and tomato real samples.

Zn Metal Atom Doping on the Surface Plane of One-Dimesional NiMoO4 Nanorods with Improved Redox Chemistry.

The effect of zinc (Zn) doping and defect formation on the surface of nickel molybdate (NiMoO4) structures with varying Zn content has been studied to produce one-dimensional electrodes and catalysts for electrochemical energy storage and ethanol oxidation, respectively. Zn-doped nickel molybdate (Ni1-xZnxMoO4, where x = 0.1, 0.2, 0.4, and 0.6) nanorods were synthesized by a simple wet chemical route. The optimal amount of Zn is found to be around 0.25 above which the NiMoO4 becomes unstable, resulting in poor electrochemical activity. This result agrees with our density functional theory calculations in which the thermodynamic stability reveals that Ni1-xZnxMoO4 crystallized in the β-NiMoO4 phase and is found to be stable for x≤0.25. Analytical techniques show direct evidence of the presence of Zn in the NiMoO4 nanorods, which subtly alter the electrocatalytic activity. Compared with pristine NiMoO4, Zn-doped NiMoO4 with the optimized Zn content was tested as an electrode for an asymmetric supercapacitor and demonstrated an enhanced specific capacitance of 122 F g-1 with a high specific energy density of 43 W h kg-1 at a high power density of 384 W kg-1. Our calculations suggest that the good conductivity from Zn doping is attributed to the formation of excess oxygen vacancies and dopants play an important role in enhancing the charge transfer between the surface and OH- ions from the electrolyte. We report electrochemical testing, material characterization, and computational insights and demonstrate that the appropriate amount of Zn in NiMoO4 can improve the storage capacity (∼15%) due to oxygen vacancy interactions.

Application of carbon nanoonion-NiMoO4-MnWO4 nanocomposite for modification of glassy carbon electrode: Electrochemical determination of ascorbic acid

In this paper, sonochemical synthesized nanocomposite was used in the construction of an electrochemical sensor. Decorated carbon nanoonions (CNOs) with nickel molybdate (NiMoO4) and manganese tungstate (MnWO4) nanocomposite were used to modify the glassy carbon electrode (GCE). The high conductivity and large surface area of the CNOs and the electrocatalytic effect of NiMoO4 and MnWO4 nanocomposite provide a synergistic effect on the electrooxidation processes. The modified GCE surface with a synthesized nanocomposite of CNO-NiMoO4-MnWO4 was used to determine ascorbic acid using differential pulse voltammetry (DPV) method. The developed ascorbic acid sensor displayed a wide dynamic calibration range (1–100 μM) with trace level LOD (0.33 μM) and appropriate sensitivity (0.1768 μA μM−1cm−2). The determination of ascorbic acid in the serum and urine as the real samples exhibited a reasonable relative recovery in the range of 100–104%.

Direct Observation of Ni–Mo Bimetallic Catalyst Formation via Thermal Reduction of Nickel Molybdate Nanorods

We used in situ environmental transmission electron microscopy to image the formation of a Ni–Mo composite nanocatalyst via thermal reduction of NiMoO4 nanorods. Two clear structural changes were o...

Preparation of highly active unsupported Ni–Si–Mo catalyst for the deep hydrogenation of aromatics

Abstract A mesoporous nickel-silicon-molybdenum composite oxide with the phase of ammonium nickel (or silicon) molybdate was synthesized by chemical precipitation and unsupported nickel-silicon-molybdenum sulfide catalysts with various Ni/Si ratios were obtained by sulfidation of the oxide precursors. The oxide precursors and unsupported sulfide catalysts were characterized by XRD, N2 adsorption-desorption, SEM, TPR, and HRTEM. The unsupported nickel-silicon-molybdenum sulfide catalysts were tested in the hydrogenation of naphthalene. It was found that the introduction of Si could increase the specific surface area and improve the pore structure of precursors, and reduce the reduction temperature of Mo species. The results of naphthalene hydrogenation showed that the introduction of Si could significantly improve the hydrogenation activity of the catalysts, especially the Ni9.5Si0.5Mo10 catalyst exhibited the highest aromatic hydrogenation activity at low temperature. Interestingly, it is found that the tetralin selectivity is 100% in the low temperature range (220–260 °C) over Si10Mo10 catalyst, which might be attractive in the production of tetralin and other industrial application.

Rational design and construction of nickel molybdate nanohybrid composite for high-performance supercapattery

Transition metal molybdates have attracted considerable devotion as a promising electrode material for energy storage devices owing to their enriched redox activity, good electronic conductivity, and stable crystal structure. Herein, we prepared the nickel molybdate (NiMoO4) nanohybrid composite on nickel (Ni) foam using a one-step hydrothermal method without using binders. The synthesized NiMoO4 material exhibited intertwined nanoflowers deposited nanosheets (NiMoO4 NFs@NSs). The high surface area of NFs and hierarchically connected NSs with open-porous voids and compact binding of nanohybrid morphology with Ni foam improve the electrochemical performance of the prepared material. Utilizing the morphological and active material features, the NiMoO4 NFs@NSs/Ni foam electrode exhibited a maximum specific capacity of 216 mA h/g (1989 F/g) at 3 mA/cm2. In addition, the prepared electrode demonstrated excellent cycling stability without fading even after long-term cycling. Furthermore, the supercapattery device was assembled with NiMoO4 NFs@NSs/Ni foam as a positive electrode and activated carbon as a negative electrode to investigate the practical applicability of the positive electrode. The fabricated supercapattery exhibited good energy storage performance, including a high specific capacitance of 38.6 F/g along with maximum energy and power densities of 13.2 W h/kg and 1644 W/kg, respectively. The potency of supercapattery in real-time feasibility was explored by operating different electronic components.