Search Results (39)

Silver nanowires (Ag NWs) are of great importance for modern applications as a substitute for indium tin oxide (ITO) when flexible, transparent conductive electrodes are required. In this paper, we report for the first time the electrical resistivity (ρ) of an isolated Ag nanowire not supported on a substrate, measured using transmission electron microscopy (TEM). Our results show a resistivity value on the order of 10⁻⁷ Ω-m, which is significantly higher than that of the bulk silver, which is 1.59 × 10⁻⁸ Ω-m. We attribute the reduction in electrical conductivity to three main factors: (i) surface scattering, (ii) internal boundaries, and (iii) internal stress. The electrical conductivity of Ag/Ni nanowires was also evaluated. The deposition of Ni layers onto Ag NWs forms a core–shell structure, resulting in a slight decrease in resistance comparable to Ag nanowires. This indicates that electrical transport is mainly governed by the highly conductive Ag core, whereas the Ni shell plays an indirect role through structural stabilization and modulation of surface states and scattering mechanisms, rather than directly enhancing intrinsic conductivity. Full article

To address the application requirements of energy storage devices for new energy electric vehicles—including high energy density, high-power density, fast charging and discharging, and long-term cycling stability—traditional symmetric supercapacitors are often limited by low energy density and poor compatibility between the anode and cathode, making it difficult to meet the high-efficiency energy storage demands under the dynamic operating conditions of electric vehicles. This study focuses on the regulation of hierarchical thin-film structures and the innovative heterogeneous coating interface engineering with precise slurry coating and film-forming optimization and designs and fabricates NiCo₂O₄/NiFeO composite thin-film electrodes and Mn-doped porous carbon (Mn-PC) thin-film electrodes. The uniform, compact and stable coating formation on nickel foam substrates via controllable slurry coating facilitates the efficient integration of active materials and conductive supports. The electrode slurries were coated onto conductive nickel foam substrates, and high-performance aqueous supercapacitors were assembled using an asymmetric configuration. A systematic study was conducted covering material preparation, structural characterization, electrochemical testing, and full-device performance evaluation. Using techniques such as XRD, XPS, SEM, TEM, BET, and an electrochemical workstation, the study revealed the structure–activity relationships among material morphology, crystalline phases, pore structure, and electrochemical performance, elucidating the charge storage mechanisms of the composite electrode films and the principles of synergistic adaptation between the anode and cathode. The results indicate that NiCo₂O₄ nanowires decorated with in situ-grown NiFeO nanosheets to form a composite structure; when coated onto nickel foam, this forms a uniform, porous electrode film with a specific surface area of 171.3 m²/g, a specific capacitance as high as 1746 F/g at 1 A/g, and a capacity retention rate of 94.0% after 10,000 cycles. After coating and film formation, the Mn-PC anode introduced pseudocapacitive active sites through uniform Mn doping, resulting in a film electrode specific capacitance of 348 F/g and significantly improved rate and cycling performance. The assembled NiCo₂O₄/NiFeO//Mn-PC asymmetric supercapacitor exhibits a thin-film electrode specific capacitance of 153 F/g at 1 A/g, with a maximum energy density of 52 Wh/kg. Even at a power density of 9000 W/kg, it maintains 45 Wh/kg, and retains 89.5% of its capacity after 10,000 cycles, with overall performance outperforming most previously reported transition metal-based devices. This coating-engineered electrode fabrication strategy breaks through the interface mismatch and structural instability bottlenecks of traditional thin-film electrodes, providing a novel material system and an efficient coating assembly strategy for high-performance supercapacitor thin-film electrodes in new energy electric vehicles, and offers experimental evidence and technical references for the development and application of high-power energy storage coating devices for automotive use, as well as the innovative design of electrode coating engineering in energy storage fields. Full article

Oxygen evolution reaction (OER), a pivotal half-reaction in water splitting and renewable energy conversion, suffers from intrinsically sluggish kinetics, necessitating robust electrocatalysts to lower overpotential and enhance energy efficiency. Nickel-based substrates are particularly appealing due to their ability to form compact and stable oxide layers; however, rationally constructing high-surface-area Ni supports remains a substantial challenge. Here, we develop a synergistic electrodeposition–etching strategy to fabricate clustered NiZn alloy nanowires on Ni foils, followed by mild chemical oxidation. This treatment that induces surface oxidation, promotes Fe incorporation, and drives in situ reconstruction into a nanosheet-like NiFeZn(OH)_x catalytic layer. This integrated approach overcomes common issues associated with electrodeposited coatings on NiZn nanowire clusters, including poor hydrophilicity, weak adhesion, and uncontrollable morphology. The optimized NiFeZn(OH)_x/NiZn/Ni electrode delivers outstanding OER performance in 1 M KOH, requiring only 229 mV to reach 100 mA cm⁻², with a low Tafel slope of 31.6 mV dec⁻¹, and demonstrates exceptional durability over 180 h of continuous operation without performance degradation. The superior catalytic behavior originates from the synergistic interplay between the high-surface-area NiZn nanowire scaffold and the dynamically reconstructed NiFeZn(OH)_x active phase. This work provides a generalizable strategy for engineering efficient and durable OER electrodes, offering new design principles for Ni-based alloy supports in advanced electrocatalysis. Full article

This paper presents a novel approach for fabricating porous NiO films decorated with nanowires, achieved through sputtering followed by thermal oxidation of a metallic layer. Notably, we successfully fabricate NiO nanowires using this simple and cost-effective method, demonstrating its potential applicability in the gas-sensing field. Furthermore, by using the film of our nanowires, we are able to easily prepare NiO sensors and deposit the required Pt electrodes directly on the film. This is a key advantage, as it simplifies the fabrication process and makes it easier to integrate the sensors into practical gas-sensing devices without the need for nanostructure transfer or intricate setups. Scanning electron microscopy (SEM) reveals the porous structure and nanowire formation, while X-ray diffraction (XRD) confirms the presence of the NiO phase. As a preliminary investigation, the gas-sensing properties of NiO films with varying thicknesses were evaluated at different operating temperatures. The results indicate that thinner layers exhibit superior performances. Gas measurements confirm the p-type nature of the NiO samples, with sensors showing high responsiveness and selectivity toward NO₂ at an optimal temperature of 200 °C. However, incomplete recovery is observed due to the high binding energy of NO₂ molecules. At higher temperatures, sufficient activation energy enables a full sensor recovery but with reduced response. The paper discusses the adsorption–desorption reaction mechanisms on the NiO surface, examines how moisture impacts the enhanced responsiveness of Pt-NiO (2700%) and Au-NiO (400%) sensors, and highlights the successful fabrication of NiO nanowires through a simple and cost-effective method, presenting a promising alternative to more complex approaches. Full article

Nickel hydroxide has ultra-high energy storage capacity in supercapacitors, but poor electrical conductivity limits their further application. The use of graphene to improve its conductivity is an effective measure, but how to suppress the stacking of graphene and improve the overall performance of composite materials has become a new challenge. In this work, a well-designed substrate of N-doped carbon nanowires with reduced graphene oxide (NCNWs/rGO) was fabricated by growing polypyrrole (PPy) nanowires between GO nanosheets layers and then calcining them at high temperatures. This NCNWs/rGO substrate can effectively avoid the stacking of rGO nanosheets, and provides sufficient sites for the subsequent in situ growth of Ni(OH)₂, forming a uniform and stable Ni(OH)₂/NCNWs/rGO composite material. Benefiting from the abundant pores, high specific surface area (107.2 m² g⁻¹), and conductive network throughout the NCNWs/rGO substrate, the deposited Ni(OH)₂ can not only realize an ultra-high loading ratio, but also exposes more active surfaces (221.3 m² g⁻¹). After a comprehensive electrochemical test, it was found that the Ni(OH)₂/NCNWs/rGO positive materials have a high specific capacitance of 2016.6 F g⁻¹ at a scan rate of 1 mV s⁻¹, and exhibit significantly better stability. The assembled Ni(OH)₂/NCNWs/rGO//AC asymmetric supercapacitor could achieve a high energy density of 85.2 Wh kg⁻¹ at power densities of 381 W kg⁻¹. In addition, the asymmetric supercapacitor has excellent stability and could retain 70.1% of initial capacitance after 10,000 cycles. These results demonstrate the feasibility of using NCNWs/rGO substrate to construct high-performance supercapacitor electrode materials, and it is also expected to be promoted in other active composite materials. Full article

The Co₃O₄ nanowire@NiCo₂O₄ nanosheet hierarchical array was constructed on Ni foam using hydrothermal and annealing approaches in turn, from which a NiCo₂O₄ nanosheet could self-assemble on the Co₃O₄ nanowire. The structure and morphology of the Co₃O₄ nanowire@NiCo₂O₄ nanosheet hierarchical array were characterized via XRD, EDS, SEM, and FESEM, respectively. The electrochemical performance of the composite array was measured via a cyclic voltammetry curve, galvanostatic current charge–discharge, charge–discharge cycle, and electrochemical impedance and then compared with the Co₃O₄ nanowire. The results show that the Co₃O₄ nanowire@NiCo₂O₄ nanosheet hierarchical array could reach a high value of 2034 F g⁻¹ at a current density of 2.5 A g⁻¹. After 5000 galvanostatic charge–discharge cycles, the specific capacitance of the Co₃O₄ nanowire@NiCo₂O₄ nanosheet hierarchical array could still maintain 94.7% of the original value. Therefore, the Co₃O₄ nanowire@NiCo₂O₄ nanosheet hierarchical array would be a desirable electrode material for a high-performance supercapacitor. Full article

The electrochemical removal of abundant and toxic H₂S from highly sour reservoirs has emerged as a promising method for hydrogen production and desulfurization. Nevertheless, the ineffectiveness and instability of current electrocatalysts have impeded further utilization of H₂S. In this communication, we introduce a robust array of Fe₂NiSe₄ nanowires synthesized in situ on a FeNi₃ foam (Fe₂NiSe₄/FeNi₃) via hydrothermal treatment. This array acts as an active electrocatalyst for ambient H₂S splitting. It offers numerous exposed active sites and a rapid electron transport channel, significantly enhancing charge transport rates. As an electrode material, Fe₂NiSe₄/FeNi₃ displays remarkable electrocatalytic efficiency for both sulfide oxidation and hydrogen evolution reactions. This bifunctional electrode achieves efficient electrochemical H₂S splitting at a low potential of 440 mV to reach a current density of 100 mA∙cm⁻², with a faradaic efficiency for hydrogen production of approximately 98%. These findings highlight its significant potential for desulfurization and energy-efficient hydrogen generation. Full article

Ni nanowire array electrodes with an extremely large surface area were made through an electrochemical reduction process utilizing an anodized alumina template with a pore length of 320 µm, pore diameter of 100 nm, and pore aspect ratio of 3200. The electrodeposited Ni nanowire arrays were preferentially oriented in the (111) plane regardless of the deposition potential and exhibited uniaxial magnetic anisotropy with easy magnetization in the axial direction. With respect to the magnetic properties, the squareness and coercivity of the electrodeposited Ni nanowire arrays improved up to 0.8 and 550 Oe, respectively. It was also confirmed that the magnetization reversal was suppressed by increasing the aspect ratio and the hard magnetic performance was improved. The electrocatalytic performance for hydrogen evolution on the electrodeposited Ni nanowire arrays was also investigated and the hydrogen overvoltage was reduced down to ~0.1 V, which was almost 0.2 V lower than that on the electrodeposited Ni films. Additionally, the current density for hydrogen evolution at −1.0 V and −1.5 V vs. Ag/AgCl increased up to approximately −580 A/m² and −891 A/m², respectively, due to the extremely large surface area of the electrodeposited Ni nanowire arrays. Full article

The rational fabrication of composite structures made of mixed components has shown great potential for boosting the energy density of supercapacitors. Herein, an elaborate hierarchical MOF-derived NiCo₂S₄@Mo-doped Co-LDH arrays hybrid electrode was fabricated through a step-wise method. By leveraging the synergistic effects of a uniform array of NiCo₂S₄ nanowires as the core and an MOF-derived porous shell, the NiCo₂S₄@Mo-doped Co-LDH hybrid electrode demonstrates an exceptional specific capacitance of 3049.3 F g⁻¹ at 1 A g⁻¹. Even at a higher current density of 20 A g⁻¹, the capacitance remains high at 2458.8 F g⁻¹. Moreover, the electrode exhibits remarkable cycling stability, with 91% of the initial capacitance maintained after 10,000 cycles at 10 A g⁻¹. Additionally, the as-fabricated asymmetric supercapacitor (ASC) based on the NiCo₂S₄@Mo-doped Co-LDH electrode achieves an impressive energy density of 97.5 Wh kg⁻¹ at a power density of 835.6 W kg⁻¹. These findings provide a promising approach for the development of hybrid-structured electrodes, enabling the realization of high-energy-density asymmetric supercapacitors. Full article

Ternary transition metal phosphides (TTMPs) with two-dimensional heterointerface and adjustable electronic structures have been widely studied in hydrogen evolution reactions (HER). However, single-phase TMPs often have inappropriate H* adsorption energy and electronic transfer efficiency in HER. Herein, we utilized the heterogeneity in the crystal structure to design an efficient and stable catalyst from the NiCoP nanowire@NiCoP nanosheet on nickel foam (NW-NiCoP@NS-NiCoP/NF) for HER. Layered double hydroxides (LDHs) with a heterogeneous matrix on crystal surfaces were grown under different reaction conditions, and non-metallic P was introduced by anion exchange to adjust the electronic structure of the transition metals. The hierarchical structure of homologous NiCoP/NF from the LDH allows for a larger surface area, which results in more active sites and improved gas diffusion. The optimized NW-NiCoP@NS-NiCoP/NF electrode exhibits excellent HER activity, with an overpotential of 144 mV, a Tafel slope of 84.2 mV dec⁻¹ at a current density of 100 mA cm⁻² and remarkable stability for more than 500 h in 1.0 M KOH electrolyte. This work provides ideas for elucidating the rational design of structural heterogeneity as an efficient electrocatalyst and the in situ construction of hierarchical structures. Full article

A one-step sulfurization method to fabricate Ni₃S₂ nanowires (Ni₃S₂ NWs) directly on a Ni foam (NF) was developed as a simple, low-cost synthesis method for use as a supercapacitor (SC), aimed at optimizing energy storage. Ni₃S₂ NWs have high specific capacity and are considered a promising electrode material for SCs; however, their poor electrical conductivity and low chemical stability limit their applications. In this study, highly hierarchical three-dimensional porous Ni₃S₂ NWs were grown directly on NF by a hydrothermal method. The feasibility of the use of Ni₃S₂/NF as a binder-free electrode for achieving high-performance SCs was examined. Ni₃S₂/NF exhibited a high specific capacity (255.3 mAh g⁻¹ at a current density of 3 A g⁻¹), good rate capability (2.9 times higher than that of the NiO/NF electrode), and competitive cycling performance (capacity retention of specific capacity of 72.17% after 5000 cycles at current density of 20 A g⁻¹). Owing to its simple synthesis process and excellent performance as an electrode material for SCs, the developed multipurpose Ni₃S₂ NWs electrode is expected to be a promising electrode for SC applications. Furthermore, the synthesis method of self-growing Ni₃S₂ NW electrodes on 3D NF via hydrothermal reactions could potentially be applied to the fabrication of SC electrodes using a variety of other transition metal compounds. Full article

Simple, low-cost methods for sensing volatile organic compounds that leave no trace and do not have a detrimental effect on the environment are able to protect communities from the impacts of contaminants in water supplies. This paper reports the development of a portable, autonomous, Internet of Things (IoT) electrochemical sensor for detecting formaldehyde in tap water. The sensor is assembled from electronics, i.e., a custom-designed sensor platform and developed HCHO detection system based on Ni(OH)₂–Ni nanowires (NWs) and synthetic-paper-based, screen-printed electrodes (pSPEs). The sensor platform, consisting of the IoT technology, a Wi-Fi communication system, and a miniaturized potentiostat can be easily connected to the Ni(OH)₂–Ni NWs and pSPEs via a three-terminal electrode. The custom-made sensor, which has a detection capability of 0.8 µM/24 ppb, was tested for an amperometric determination of the HCHO in deionized (DI) and tap-water-based alkaline electrolytes. This promising concept of an electrochemical IoT sensor that is easy to operate, rapid, and affordable (it is considerably cheaper than any lab-grade potentiostat) could lead to the straightforward detection of HCHO in tap water. Full article

The development of bifunctional electrocatalysts with high catalytic activity and cyclic stability is an effective method for electrocatalytic water splitting. Herein, a promising hydroxide/oxide Co(OH)₂/α-NiMoO₄ NWs/CC heterostructure with nanoflowers decorating the nanowires was fabricated on a carbon cloth (CC) substrate via hydrothermal and calcination methods. In contrast to one-dimensional nanomaterials, the interfaces of Co(OH)₂ nanoflowers and α-NiMoO₄ nanowires on CC provide more active sites for electrocatalytic reactions; therefore, they exhibit obviously enhanced electrocatalytic activities in overall water splitting. Specifically, the Co(OH)₂/α-NiMoO₄ NWs/CC electrodes exhibit an overpotential of 183.01 mV for hydrogen evolution reaction (HER) and of 170.26 mV for oxygen evolution reactions (OER) at the current density of 10 mA cm⁻² in 1.0 M KOH. Moreover, the electrocatalytic oxygen evolution reaction (OER) activity of the Co(OH)₂/α-NiMoO₄ NWs/CC electrocatalyst was enhanced after long-term stability tests. Full article

The development of responsive materials in a predictable manner is high on the list of the material industry’s trends. In this work, responsive Ag@NiCo₂O₄ nanowires were, firstly, anchored on N-doped carbon cloth (NC) and, then, employed as array electrodes for a nonenzymatic glucose-sensing application. The results showed that the highly conductive NiCo₂O₄ nanowires supported Ag nanoparticles and exhibited high conductivity and electrocatalytic properties. The fully exposed crystalline planes of Ag nanoparticles provided more active surface sites. As a result, the assembled Ag@NiCo₂O₄-NC electrodes for the glucose-sensing evaluation delivered a selectivity of 2803 μA mM⁻¹ cm⁻² and a detection limit of 1.065 μM, which outperformed the literature-reported Ag- and NiCo₂O₄-based glucose-sensing catalysts. Full article

Oxygen evolution reaction is a key process in hydrogen production from water splitting. The development of non-noble metal electrode materials with high efficiency and low cost has become the key factor for large-scale hydrogen production. Binary NiCo-layered double hydroxide (LDH) has been used as a non-noble metal electrocatalyst for OER, but its overpotential is still large. The microstructure of the catalyst is tuned by doping Mo ions into the NiCo-LDH/NF nanowires to form ternary NiCoMo-LDH/NF nanosheet catalysts for the purpose of enhancing the active sites and reducing the initial overpotential. Only 1.5 V (vs. reversible hydrogen electrode (RHE), ≈270 mV overpotential) is required to achieve a catalytic current density of 10 mA cm⁻² and a small Tafel slope of 81.46 mV dec⁻¹ in 1 M KOH solution, which manifests the best performance of NiCo-based catalysts reported up to now. Electrochemical analysis and micro-morphology show that the high catalytic activity of NiCoMo-LDH/NF is attributable to the change of the microstructure. The interconnected nanosheet arrays have the obvious advantages of electrolyte diffusion and ion migration. Thus, the active sites of catalysts are significantly increased, which facilitates the adsorption and desorption of intermediates. We conclude that NiCoMo-LDH/NF is a promising electrode material for its low cost and excellent electrocatalytic properties. Full article