NiMoO4 Nanowires Research Articles

Electron Manipulation and Surface Reconstruction of Bimetallic Iron-Nickel Phosphide Nanotubes for Enhanced Alkaline Water Electrolysis.

Developing high-efficiency and stable bifunctional electrocatalysts for water splitting remains a great challenge. Herein, NiMoO4 nanowires as sacrificial templates to synthesize Mo-doped NiFe Prussian blue analogs are employed, which can be easily phosphorized to Mo-doped Fe2xNi2(1-x)P nanotubes (Mo-FeNiP NTs). This synthesis method enables the controlled etching of NiMoO4 nanowires that results in a unique hollow nanotube architecture. As a bifunctional catalyst, the Mo-FeNiP NTs present lower overpotential and Tafel slope of 151.3 (232.6) mV at 100 mA cm-2 and 76.2 (64.7) mV dec-1 for HER (OER), respectively. Additionally, it only requires an ultralow cell voltage of 1.47 V to achieve 10 mA cm-2 for overall water splitting and can steadily operate for 200 h at 100 mA cm-2. First-principles calculations demonstrate that Mo doping can effectively adjust the electron redistribution of the Ni hollow sites to optimize the hydrogen adsorption-free energy for HER. Besides, in situ Raman characterization reveals the dissolving of doped Mo can promote a rapid surface reconstruction on Mo-FeNiP NTs to dynamically stable (Fe)Ni-oxyhydroxide layers, serving as the actual active species for OER. The work proposes a rational approach addressed by electron manipulation and surface reconstruction of bimetallic phosphides to regulate both the HER and OER activity.

Tailoring the electronic structure of NiMoO4 nanowires with NiCo2O4 nanosheets by constructing heterostructure interfaces for improving oxygen evolution reaction

Tailoring the electronic structure of NiMoO4 nanowires with NiCo2O4 nanosheets by constructing heterostructure interfaces for improving oxygen evolution reaction

Developing NiMoO4-based multifunctional cathode for hybrid zinc battery.

Herein, we developed a multifunctional cathode (Co-NiMoO4/NF) based on nickel molybdate nanowires grown on Ni foam (NiMoO4/NF) for a hybrid zinc-nickel (Zn-Ni) and zinc-air (Zn-Air) battery. NiMoO4/NF demonstrated a high capacity and good rate capability in the Zn-Ni battery. The subsequent coating of the Co-based oxygen catalyst resulted in the Co-NiMoO4/NF and enabled the battery to exhibit the advantages of both batteries.

A Two-Dimensional NiMoO4 Nanowire Electrode for the Sensitive Determination of Hydroquinone in Four Types of Actual Water Samples

A Two-Dimensional NiMoO4 Nanowire Electrode for the Sensitive Determination of Hydroquinone in Four Types of Actual Water Samples

Facile Synthesis of N and P Co-Doped NiMoO4 Hollow Nanowires and Electrochemical Deposition of NiFe-Layered Double Hydroxide for Boosting Overall Seawater Splitting

NiMoO4 (NM) nanowires coated on nickel foam (NF) were prepared by the facile hydrothermal method. After calcination at low temperature, the nitrogen and phosphorus were co-doped into bimetal NF@NM nanowires. The hollow nanowire structure could be obtained after low-temperature calcination and nonmetallic doping. The as-synthesized hollow NF@NiMoO4/N/P (NF@NM-NP) nanowires exhibit excellent hydrogen evolution reaction performance (with an overpotential of −164 mV at −100 mA cm−2) due to the existence of planar defects and the hollow structure. To further improve the catalytic activity in the oxygen evolution reaction, amorphous lamellar NiFe-layered double hydroxide (NiFe LDH) was deposited onto the NF@NM-NP nanowires via an electrochemical method to form core–shell NF@NM-NP@NiFe LDH, which deliver an overpotential of 218 mV at 100 mA cm−2. Furthermore, an asymmetric setup composed of NF@NM-NP hollow nanowires and core–shell NF@NM-NP@NiFe LDH electrode were fabricated for overall seawater splitting, which can deliver potentials of 1.46 and 1.70 V at current densities of 10 and 100 mA cm−2 in simulated alkaline seawater (1 M KOH and 0.5 M NaCl), respectively. This may provide an effective path for the formation of a green energy conversion system.

Synchronous Defect and Interface Engineering of NiMoO4 Nanowire Arrays for High-Performance Supercapacitors.

Developing high-performance electrode materials is in high demand for the development of supercapacitors. Herein, defect and interface engineering has been simultaneously realized in NiMoO4 nanowire arrays (NWAs) using a simple sucrose coating followed by an annealing process. The resultant hierarchical oxygen-deficient NiMoO4@C NWAs (denoted as “NiMoO4−x@C”) are grown directly on conductive ferronickel foam substrates. This composite affords direct electrical contact with the substrates and directional electron transport, as well as short ionic diffusion pathways. Furthermore, the coating of the amorphous carbon shell and the introduction of oxygen vacancies effectively enhance the electrical conductivity of NiMoO4. In addition, the coated carbon layer improves the structural stability of the NiMoO4 in the whole charging and discharging process, significantly enhancing the cycling stability of the electrode. Consequently, the NiMoO4−x@C electrode delivers a high areal capacitance of 2.24 F cm−2 (1720 F g−1) at a current density of 1 mA cm−2 and superior cycling stability of 84.5% retention after 6000 cycles at 20 mA cm−2. Furthermore, an asymmetric super-capacitor device (ASC) has been constructed with NiMoO4−x@C as the positive electrode and activated carbon (AC) as the negative electrode. The as-assembled ASC device shows excellent electrochemical performance with a high energy density of 51.6 W h kg−1 at a power density of 203.95 W kg−1. Moreover, the NiMoO4//AC ASC device manifests remarkable cyclability with 84.5% of capacitance retention over 6000 cycles. The results demonstrate that the NiMoO4−x@C composite is a promising material for electrochemical energy storage. This work can give new insights on the design and development of novel functional electrode materials via defect and interface engineering through simple yet effective chemical routes.

In-situ probing the rapid reconstruction of FeOOH-decorated NiMoO4 nanowires with boosted oxygen evolution activity

Understanding the dynamic surface reconstruction is of vital importance for the development of oxygen evolution reaction (OER) electrocatalysts. Herein, we report FeOOH-decorated NiMoO4 nanowires as OER pre-catalysts. In-situ Raman spectroscopy elucidates that modified NiMoO4 undergoes fast reconstruction, including significant Mo leaching and simultaneous formation of Ni(Fe)OOH intermediates, which are determined as the real active species toward the OER. Rapid and deep reconstruction results in amorphous nanowires with uniform Fe distribution and great size expansion. Impressively, the reconstructed pre-catalyst exhibits outstanding catalytic activity, ultra-low overpotential, and extraordinary long-term stability under high current densities. Our work provides a facile and effective surface engineering approach of pre-catalysts and highlights the evolution of self-reconstruction chemistry for accelerating the kinetics of the OER.

Interface engineered NiFe2O4−x/NiMoO4 nanowire arrays for electrochemical oxygen evolution

Designing highly active and stable electrocatalysts for oxygen evolution reaction (OER) is the key to success in sustainable water splitting reaction, a sustainable route towards high purity hydrogen production. Interface engineering is one of the most effective strategies for modulating the local electronic structure of active sites to enhance catalytic activity. Herein, NiFe2O4−x nanoparticles were integrated to NiMoO4 nanowires (NiFe2O4−x/NMO) grown on nickel foam to construct an extended interface with strong electronic interactions. The NiFe2O4−x/NMO demonstrates high OER activities as manifested by a low overpotential of 326 mV at a high current density of 600 mA cm−2 and good long-term stability. The intimate interface between NiFe2O4−x and NiMoO4 is responsible for the Fe-facilitated phase transition to active γ-NiOOH phase as revealed by in situ Raman spectroelectrochemical studies. This study outlines how the interface design of integrated nanostructures can optimize the formation of active phase for enhanced catalytic activity.

NiMoO4 nanowires supported on Ni/C nanosheets as high-performance cathode for stable aqueous rechargeable nickel-zinc battery

Nickel-based oxides for aqueous rechargeable nickel-zinc (denoted as Ni//Zn) batteries typically suffer from the low capacity and inferior stability due to their slow electron/ion transportation rate and poor electrochemical reversibility. Here, we rationally design a free-standing Ni/C nanosheets (NC) from Ni metal-organic framework as conductive scaffold for NiMoO4 nanowires (NiMoO4-NC), achieving exceptionally high capacity and rate capability. Furthermore, with the use of a new MoO42−-based electrolyte, a stable aqueous Ni//Zn battery with impressive electrochemical performance is also demonstrated based on this NiMoO4-NC cathode. Experimental results reveal that the NC skeleton can dramatically improve the conductivity and ion diffusion rate of the NiMoO4 nanowires, while the addition of MoO42− into electrolyte can effectively suppress the dissolution and structural destruction of NiMoO4 nanowires. As a consequence, a remarkable capacity (229.2 mAh g−1 at 3.4 A g−1) and excellent durability (85.9% capacity retention after 3000 cycles) are delivered by this Ni//Zn battery, outperforming most reported Ni//Zn batteries. Also, this Ni//Zn battery displays an admirable energy density of 407.8 Wh kg−1, together with a remarkable power density of 18.1 kW kg−1, which is of great significance for future electronic application.

Three-dimensional heterostructured polypyrrole/nickel molybdate anchored on carbon cloth for high-performance flexible supercapacitors

The urgent demands of energy storage for wearable electronics necessitates the development of flexible supercapacitors (FSCs). However, the service environment of portable/wearable devices requires supercapacitors to possess excellent mechanical properties to withstand harsh straining conditions, such as bending, rolling, and twisting. Hence, to develop a high-performance flexible supercapacitor (FSC) that possesses both superior electrochemical properties and remarkable mechanical capacities is still a formidable challenge. In this paper, we successfully fabricate a 3D heterostructured electrode with bulge structured polypyrrole (PPy) wrapped NiMoO4 nanowires on carbon cloth (CC). Benefiting from the 3D heterostructure and the synergistic effect between NiMoO4 and PPy, the PPy/NiMoO4/CC electrode shows a high areal capacitance of 3.4 F cm−2 and cyclic stability (94% capacitance retention). Moreover, the assembled PPy/NiMoO4/CC//activated carbon (AC)/CC device exhibits a high energy density (0.5 mW cm−2 at a power density of 3.7 mWh cm−2). Furthermore, the CV curves of PPy/NiMoO4/CC//AC/CC show no obvious change under miscellaneous deformation conditions, indicating good flexibility. This work demonstrates that the assembled PPy/NiMoO4/CC//AC/CC FSC possesses notable electrochemical properties and exhibits great potential for application in future wearable energy-storage devices.

Homogeneous Core/Shell NiMoO4@NiMoO4 and Activated Carbon for High Performance Asymmetric Supercapacitor.

Here, we report the extraordinary electrochemical energy storage capability of NiMoO4@NiMoO4 homogeneous hierarchical nanosheet-on-nanowire arrays (SOWAs), synthesized on nickel substrate by a two-stage hydrothermal process. Comparatively speaking, the SOWAs electrode displays superior electrochemical performances over the pure NiMoO4 nanowire arrays. Such improvements can be ascribed to the characteristic homogeneous hierarchical structure, which not only effectively increases the active surface areas for fast charge transfer, but also reduces the electrode resistance significantly by eliminating the potential barrier at the nanowire/nanosheet junction, an issue usually seen in other reported heterogeneous architectures. We further evaluate the performances of the SOWAs by constructing an asymmetric hybrid supercapacitor (ASC) with the SOWAs and activated carbon (AC). The optimized ASC shows excellent electrochemical performances with 47.2 Wh/kg in energy density of 1.38 kW/kg at 0–1.2 V. Moreover, the specific capacity retention can be as high as 91.4% after 4000 cycles, illustrating the remarkable cycling stability of the NiMoO4@NiMoO4//AC ASC device. Our results show that this unique NiMoO4@NiMoO4 SOWA has great prospects for future energy storage applications.

Construction of NiMoO4/Polypyrrole Nanocomposites on Carbon Cloth As Advanced Electrodes for High Performance Flexible Supercapacitors

With the rapid development of new-generation flexible electronics, future power sources are required to be mechanically flexible and also have both high energy and large power as well as long cycle life. Flexible Supercapacitors have been widely investigated by the reasons of their excellent electrochemical performance such as high power delivery, operational safety, long cycle life and flexibility. Flexible electrodes, owing to their unique advantages like flexible and wearable, have drawn many attentions. However, there still exist some challenges to improve flexible electrode materials’ conductive property and excellent cycle stability. In this paper, NiMoO4/Polypyrrole (PPy)/carbon cloth (CC) flexible electrode is proposed, using a hydrothermal synthesis method and a chemical polymerization process, to solve these issues. The designed NiMoO4/PPy/CC electrode has following advantages: 1) the electrode is flexible, light weight, good electrical conductivity (PPy possesses higher conductivity which can ensure the conductivity of the materials). 2) the NiMoO4 nanowires can directly grow on the substrate without using any binders and provide a frame support for PPy nanoparticles cladding, which can effective reduce the charge-transfer resistance and shorten the path of ion diffusion and electron transport. 3) nanocomposites can directly provide the current channels and transfer the electrons more efficient. 4) the hybrid structure can prevent the electrode material’s damage from volume change in the charge-discharge process and prove the long cycle life. 5) the designed nanocomposites can take advantages of all good function of components and achieve a synergistic effect. So the electrode exhibits a high areal specific capacitance of 1.64 F cm-2 at a current density of 1mA cm-2 and capacitance retention 98.2% after 2000 cycles. The results showed that the NiMoO4/PPy exhibit remarkable electrochemical performance, which could be utilized as a promising pseudocapacitive electrode material for high performance flexible supercapacitors. (This paper is funded by the International Exchange Program of Harbin Engineering University for Innovation-oriented Talents Cultivation.) Figure 1

In situ growth of sandwich-like NiMoO4 nanowires/reduced graphene oxide hybrid for high-performance lithium storage

Transition metal oxide electrodes, with rational structure as well as component design and combination with carbonaceous conductive support, are widely used in high-performance lithium-ion batteries (LIBs). Herein, NiMoO4 nanowires in situ decorated on reduced graphene oxide (NiMoO4/rGO) were synthesized through a facile hydrothermal and subsequent annealing method. Due to the enhanced electrical conductivity and buffering matrix provided by rGO and the synergistic effect between NiMoO4 and rGO, the resultant NiMoO4/rGO exhibits short ion transport pathways and improved diffusion kinetics. The results reveal that NiMoO4/rGO hybrid shows much improved lithium storage performances compared with pure NiMoO4 nanowires including a high specific capacity (1212.4 mAh g−1 after 100 cycles at 0.2 A g−1), high rate capability (988.6 mAh g−1 at 2 A g−1 and 928.1 mAh g−1 at 4 A g−1) and excellent cycling performance at high current density (1007.6 mAh g−1 after 1000 cycles at 1 A g−1) when applied as anode material for LIBs, outperforming most of the reported metal molybdates-based electrodes. Besides, such excellent lithium storage performance, combined with the simple hydrothermal-annealing synthesis strategy, makes the NiMoO4/rGO a promising anode material for high-performance LIBs.

Epitaxial Heterogeneous Interfaces on N‐NiMoO4/NiS2 Nanowires/Nanosheets to Boost Hydrogen and Oxygen Production for Overall Water Splitting

AbstractDeveloping bifunctional efficient electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is in high demand for the development of overall water‐splitting devices. In particular, the electrocatalytic performance can be largely improved by designing positive nanoscale‐heterojunction with well‐tuned interfaces. Herein, a novel top‐down strategy is reported to construct the oxide/sulfide heterostructures (N‐NiMoO4/NiS2 nanowires/nanosheets) as a multisite HER/OER catalyst. Starting with the NiMoO4 nanowires, nitridation in a controlled manner enables activation of Ni sites in NiMoO4 and then yields oxide/sulfide heterojunction by directly vulcanizing the highly composition‐segregated N‐NiMoO4 nanowires. The abundant epitaxial heterogeneous interfaces at atomic‐level facilitate the electron transfer from N‐NiMoO4 to NiS2, which further cooperate synergistically toward both the hydrogen and oxygen generation in alkali solution. Furthermore, with N‐NiMoO4/NiS2 grown carbon fiber cloth as the engineering electrode, the assembled N‐NiMoO4/NiS2–N‐NiMoO4/NiS2 system can deliver a current density of 10 mA cm−2 with the cell voltage of 1.60 V in the water‐splitting reaction. This current density is 3.39 times higher than that of the Pt–Ir set (2.95 mA cm−2). The excellent catalytic performance offered of N‐NiMoO4/NiS2 nanowires/nanosheets presents a great example to demonstrate the significance of interface engineering in the field of electrocatalysis.

NiMoO4 nanowire arrays and carbon nanotubes film as advanced electrodes for high-performance supercapacitor

Self-supported NiMoO4 nanowire arrays (NNAs) are successfully grown on nickel foam (NF) via a simple one-step hydrothermal method and anneal treatment. Importantly, the in-situ growth method can reduce the contact resistance between the active material and current collector. It also can prevent the binder/conductive agent from “area of the deactivation” phenomenon. So, the design can effectively improve the electrochemical performance of electrode materials. In addition, a highly flexible carbon nanotubes (CNTs) film is also prepared by vacuumfiltrationstep. Finally, an all-solid asymmetric supercapacitor (ASC) based on the optimized NiMoO4 nanowires electrode and carbon nanotube film (CNF) is assembled with PVA/KOH gel electrolyte. The ASC device presents outstanding electrochemical performance with a high energy density of 54.3 Wh kg−1 at a power density of 4344 W kg−1. The specific capacitance of the NNAs//CNF ASC remains 91.6% after 6000 cycles with a current density of 14 A g−1. At the same time, it also can continue to work under different bending states with almost constant performance. These results reveal that the NNAs//CNF ASC has great application prospect for flexible electronic fields.

Nanowire-core/double-shell of NiMoO4@C@Ni3S2 arrays on Ni foam: insights into supercapacitive performance and capacitance degradation

The one-dimensional-core/double-shell arrays on Ni foam were prepared by the hydrothermal, carbonized and electrodeposition processes, consisting of NiMoO4 nanowire as a core, an ultrathin carbon layer as an internal shell and Ni3S2 nanosheets an external shell (abbr. NiMoO4@C@Ni3S2), respectively. The ternary heterostructure demonstrates the synergistic effect on the dimensional, interface, surface structures and compositions, resulting from the ordered and functionalized architectures. Therefore, the NiMoO4@C@Ni3S2 electrode integrated the advantages of the electron transfer, electrolyte penetration and ion diffusion. The asymmetric supercapacitor exhibited a high energy density of 1.29 mW h cm−3 at a power density of 13.99 W cm−3. Furthermore, we compared the changes in composition, structure and morphology before and after 3000 cycles using the three electrode system. These observations demonstrated that the dissolution of NiMoO4@C@Ni3S2 induced the decay of capacitance and cycling stability, suggesting that we can further develop a strategy to consolidate the electrode structure.

A Novel Bimetallic Nickel–Molybdenum Carbide Nanowire Array for Efficient Hydrogen Evolution

The design and fabrication of noble-metal-free hydrogenevolution electrocatalysts with high activity is significant to future renewable energy systems. In this work, self-supported NiMo carbide nanowires on carbon cloth (Ni3 Mo3 C@NPC NWs/CC; NPC=N,P-doped carbon) were developed through an electropolymerization-assisted procedure. During the synthesis process, NiMoO4 nanowires were first grown on CC through a hydrothermal reaction that was free of any polymer binder such as Nafion. By use of electropolymerization, the as-prepared NiMoO4 NWs/CC sample was then coated by a layer of polypyrole (PPy) that served as the carbon source for subsequent conversion into Ni3 Mo3 C@NPC NWs/CC by carbothermal reduction. The experimental results indicated that judicious choices of the amount of coated PPy and the pyrolysis temperature were essential for obtaining the pure-phase, nanowire array structure of Ni3 Mo3 C@NPC NWs/CC. Benefitting from the pure phase of the bimetallic carbide, the unique architecture of the nanowire array, and its self-supported nature, the optimized Ni3 Mo3 C@NPC NWs/CC electrode exhibited excellent performance in the hydrogen evolution reaction (HER) in both acidic and alkaline media. Low overpotentials of 161 and 215 mV were required to afford a high current density of 100 mA cm-2 toward the HER in acidic and alkaline media, respectively, and the catalytic activity was maintained for at least 48 h, which puts Ni3 Mo3 C@NPC NWs/CC among the best HER electrocatalysts based on metallic carbides yet reported.

Prereduction of Metal Oxides via Carbon Plasma Treatment for Efficient and Stable Electrocatalytic Hydrogen Evolution.

Prereduction of transition metal oxides is a feasible and efficient strategy to enhance their catalytic activity for hydrogen evolution. Unfortunately, the prereduction via the common H2 annealing method is unstable for nanomaterials during the hydrogen evolution process. Here, using NiMoO4 nanowire arrays as the example, it is demonstrated that carbon plasma (C-plasma) treatment can greatly enhance both the catalytic activity and the long-term stability of transition metal oxides for hydrogen evolution. The C-plasma treatment has two functions at the same time: it induces partial surface reduction of the NiMoO4 nanowire to form Ni4 Mo nanoclusters, and simultaneously deposits a thin graphitic carbon shell. As a result, the C-plasma treated NiMoO4 can maintain its array morphology, chemical composition, and catalytic activity during long-term intermittent hydrogen evolution process. This work may pave a new way for simultaneous activation and stabilization of transition metal oxide-based electrocatalysts.

Hierarchical three-dimensional NiMoO4-anchored rGO/Ni foam as advanced electrode material with improved supercapacitor performance

Designing a novel, efficient and cost-effective nanocomposite with the advantage of robust structure and outstanding conductivity is highly promising for the electrode materials of high-performance supercapacitors. Herein, we designed and synthesized a hierarchical structured NiMoO4@rGO/NF via a facile and scalable approach by growing NiMoO4 nanowires onto the skeleton of reduced graphene oxide (rGO)/Ni foam (NF). The as-made NiMoO4@rGO/NF exhibits a superior electrochemical behavior owing to the coupling effect of homogeneous NiMoO4 nanowires and high conductivity of rGO, and it exhibits a superb capacitance value of 1877 F g−1 at 1 A g−1 and shows a ultralong life span with over 98% capacitance retention after 4000 cycles at 5 A g−1 in 2 M KOH electrolyte. Moreover, an asymmetric device employing NiMoO4@rGO/NF composite and activated carbon is assembled with an aqueous electrolyte, and it displays a maximum energy density of 40 Wh kg−1 at a specific power 218.2 W kg−1. Interestingly, the asymmetric device can remain 111.2% of its initial value even after 8000 charge/discharge cycles. These results demonstrate that the NiMoO4@rGO/NF binder-free electrode provides greatly enhanced electrochemical performance and shows promising application as an anode for energy storage.

Activation of defective nickel molybdate nanowires for enhanced alkaline electrochemical hydrogen evolution.

Designing highly-efficient and cost-effective electrocatalysts for the hydrogen evolution reaction (HER) in an alkaline solution is more complex and sluggish than for an acidic one. Herein, we report a controllable N-doping strategy to synthesize a series of N-doped porous metallic NiMoO4 nanowires with concomitant oxygen vacancy defects (N-Vo-NiMoO4 NWs) for promoting the alkaline HER ability and durability. Both experimental and theoretical results demonstrate that the doped-N at NiO6 octahedral sites and the abundant oxygen vacancy defects confined in N-Vo-NiMoO4 NWs with modified electronic arrangement could enhance the metallic conductivity, affect the surface areas, and lower the adsorption energy of hydrogen, resulting in an increased HER property. However, the excess doped-N leads to an opposite effect due to the reduced valence state of Ni centres. Therefore, alkaline HER ability of N-Vo-NiMoO4 NWs exhibits a volcano-like trend vs. the nitrogen content, with N3-Vo-NiMoO4 NWs being the best one. As a result, the N3-Vo-NiMoO4 NWs show nearly zero onset overpotential, an overpotential of 55 mV at 10 mA cm-2, and a Tafel slope of only 38 mV dec-1 in 1.0 M KOH, which are superior to those of state-of-the-art platinum-free electrocatalysts.