Search Results (52)

Self-supported electrodes that combine high activity, durability, and low-cost manufacturing are essential for scalable alkaline water electrolysis. Here, we report a one-pot, high-current-density electrodeposition platform that grows Ni-rich bimetallic catalysts directly on a carbon fabric derived from a mass-produced bamboo-cellulose kitchen wipe (bamboo-derived carbon fabric, BCF). Using a single NiCl₂/NH₄Cl base bath containing 5 mM of a selectable secondary metal ion (Ce, Fe, W, or Mo), galvanostatic deposition at 1 A cm⁻² for 15 min produces conformal polycrystalline catalyst shells on the individual carbon fibers. The Ce-containing cathode (BCF@NiCe) delivers hydrogen evolution overpotentials of 96.8 mV at 20 mA cm⁻² and 222 mV at 1 A cm⁻², rivaling a Pt/C benchmark on the same substrate at industrially relevant current densities, which is attributed to the cooperative interface between metallic Ni and nanocrystalline, oxygen-vacancy-rich CeO_2−x together with a superhydrophilic fibrous architecture that releases fine H₂ microbubbles. Adding Fe to the same bath yields a Ni–Fe–Ce anode (BCF@NiFeCe) that outperforms a RuO₂ benchmark for oxygen evolution above 0.1 A cm⁻² (η = 312 mV at 0.1 A cm⁻²) with a Tafel slope of 60 mV dec⁻¹. Both electrodes operate stably for 200 h of continuous electrolysis, with the Ni/CeO_2−x nanostructure, the oxygen-vacancy population, and the surface chemical states fully preserved after the test, and the same protocol extends to Ni–W and Ni–Mo on nickel foam, establishing a versatile, low-cost route to high-current-density electrodes for green hydrogen production. Full article

Electrocatalytic glycerol oxidation to formic acid (FA) offers a sustainable route for biomass valorization, yet non-noble metal catalysts generally suffer from sluggish C-C bond cleavage and poor product selectivity. Here we report an amorphous nickel–cobalt oxyhydroxide bearing both metal and oxygen vacancies (D-NiCoO_xH_y-V_Cr,O), grown on nickel foam via one-step electrodeposition followed by electrochemical activation with Cr doping. The coexistence of the dual vacancies is experimentally confirmed by X-ray photoelectron spectroscopy (XPS), which reveals elevated Ni³⁺/Co³⁺ ratios and reduced lattice oxygen, and by electron paramagnetic resonance (EPR), which shows a markedly enhanced signal at g = 2.003. Building on prior Cr-leaching approaches in single-metal nickel oxides, this work extends dual-vacancy engineering to an amorphous bimetallic NiCo oxyhydroxide and correlates the defect structure with glycerol-induced interfacial responses, charge-transfer behavior, and product selectivity. The catalyst delivers 200 mA cm⁻² at 1.31 V vs. RHE and achieves 100% Faradaic efficiency for formate at 1.32 V vs. RHE. In situ electrochemical impedance spectroscopy further reveals a significantly reduced charge-transfer resistance. These results establish Cr-assisted dual-vacancy engineering in amorphous bimetallic oxyhydroxides as a promising strategy for selective biomass electrooxidation. Full article

Benefiting from outstanding thermal durability at elevated temperatures and eco-friendly characteristics, oxide-based thermoelectric substances exhibit great application potential in residual heat recycling and intelligent textile defect inspection. Zinc oxide (ZnO) exhibits excellent thermal stability but suffers from high lattice thermal conductivity and low carrier concentration. Herein, we systematically investigate Ni-doped ZnO ceramics. XRD(X-ray diffraction) confirms homogeneous wurtzite solid solutions with lattice contraction following Vegard’s law. Ni doping enhances electrical conductivity from 45.45 to 145.80 S·cm⁻¹ by promoting oxygen vacancy formation, while first-principles calculations reveal a narrowed bandgap. For specimens with x ranging from 0.0040 to 0.0044, the power factor attains approximately 8.0 μW·cm⁻¹·K⁻² at 873 K, representing a 41% enhancement. Meanwhile, intensified phonon scattering leads to an evident suppression of lattice thermal conductivity, which lowers the overall thermal conductivity down to 2.38 W·m⁻¹·K⁻¹ under 873 K. Benefiting from the above optimizations, the sample delivers a peak thermoelectric figure of merit (ZT) value of 0.27 at this temperature, which is 170% greater than that of undoped ZnO. In addition, the Vickers hardness rises from 242.70 HV to 281.45 HV. Such observations verify that nickel doping can successfully decouple charge and heat transport behaviors. This approach provides a feasible route toward developing oxide thermoelectric systems with upgraded thermoelectric performance. Full article

Ce-modified MnCo₂O₄ flower-like nanosheet electrodes were prepared on nickel foam by a hydrothermal-calcination route and sequentially optimized with respect to reaction time, nominal Ce content, and PVP addition. Comparative SEM, XRD, XPS, and N₂-sorption analyses identify MnCo₂O₄-9 h-3%Ce-PVP as the optimized electrode, with an open hierarchical nanosheet network and a BET surface area of 210.0 m² g⁻¹. The direct XRD/XPS control comparison distinguishes Ce-associated lattice and surface-state changes from PVP-associated synthesis effects without treating either trend as proof of substitutional Ce occupancy or quantitatively established oxygen vacancies. Likewise, PVP is treated as a morphology-directing additive whose transient adsorption or bridging role remains a synthesis hypothesis rather than a directly verified molecular mechanism. The optimized positive electrode delivers 2008 F g⁻¹ at 1 A g⁻¹, retains 1227 F g⁻¹ at 20 A g⁻¹, and shows 99.0% capacitance retention after 10,000 cycles at 5 A g⁻¹. A carbon-supported iron oxide negative electrode, designated C/Fe₂O₃ only as a sample label because its exact oxide phase was not independently resolved by XRD or Raman spectroscopy, provides 443 F g⁻¹ at 1 A g⁻¹. The resulting charge-balanced asymmetric device operates over 0–1.6 V and delivers 34.6 F g⁻¹ at 1 A g⁻¹, corresponding to 12.30 Wh kg⁻¹ at 0.8 kW kg⁻¹. At 10 A g⁻¹, it retains 29.8 F g⁻¹ and delivers 10.60 Wh kg⁻¹ at 8.0 kW kg⁻¹, equivalent to 86.1% capacitance retention over a tenfold increase in current density. All device-level gravimetric values are calculated using the total active mass of both electrodes. Full article

Hydrogen is a clean energy carrier essential for carbon neutrality, but its invisible and odorless nature poses significant safety risks, particularly during low-concentration leaks. Although metal oxide semiconductor (MOS) sensors offer fast response and high sensitivity, their ability to detect ppb-level hydrogen remains limited. In this work, we present a high-performance hydrogen gas sensor based on nickel-doped tin dioxide (Ni-SnO₂) nanorods, directly grown on planar electrodes via aerosol-assisted chemical vapor deposition (AACVD). By optimizing the Ni doping ratio and nanorod morphology, the 3 wt% Ni-SnO₂ sensor achieves a low detection limit of 100 ppb for H₂, demonstrating promising potential for low-concentration hydrogen detection. Moreover, the sensor exhibits outstanding selectivity, with a response to 100 ppm H₂ nearly six times higher than that to the next most responsive interfering gas (NH₃). Comprehensive XPS and Raman analyses reveal that Ni doping introduces abundant oxygen vacancies and lattice defects, which are the key origins of the enhanced sensing performance. Notably, the 3 wt% Ni-SnO₂ sensor strikes an optimal balance between lattice defects and structural stability, delivering both high sensitivity and good moisture resistance with minimal baseline drift over weeks of operation. This work establishes a facile and scalable AACVD strategy for engineering defect-rich SnO₂ nanostructures, enabling sub-ppm hydrogen detection with high selectivity and long-term stability—addressing a critical gap in practical hydrogen safety monitoring. Full article

This study investigates the modulation of coercivity and magnetodielectric coupling in heat-treated, nickel-substituted lanthanum ferrite. LaFe_0.7Ni_0.3O₃ samples were synthesized by high-energy ball milling and sintered at temperatures between 1073 and 1473 K. Chemical composition, crystalline structural evolution, surface morphology, magnetic, dielectric, and electrical properties, as well as magnetodielectric coupling, were analyzed. The XPS spectra revealed the presence of adsorbed oxygen, associated with the high oxygen affinity of the material. This behavior is interpreted as a charge-compensation mechanism, related both to the formation of oxygen vacancies and to the partial oxidation of Fe³⁺ to Fe⁴⁺. XRD and Rietveld refinement confirmed a single-phase orthorhombic Pnma structure, and structural simulations revealed progressive octahedral distortions with increasing temperature, affecting the octahedral tilting and electronic bandwidth. Magnetic characterization revealed that thermal processing modifies the magnetic behavior, inducing weak ferromagnetism and a significant increase in coercivity, correlating with progressive densification, greater domain stability, and reduced microstrain. Impedance measurements revealed magnetodielectric coupling, the Maxwell–Wagner interfacial polarization mechanism, and reduced dielectric losses. These findings demonstrate that the coercivity and magnetodielectric response in cationic nickel-substituted lanthanum ferrite can be tuned through thermal processing. A semi-empirical magnetocrystalline anisotropy model is proposed to explain the coercivity evolution and associated multiferroic behaviors, thus contributing to the study of functional ferrites as sustainable alternatives to rare-earth magnetic materials with potential in sensors and memory devices. Full article

In electrochemical nitrite detection, the strong oxidizing nature of nitrite often leads to high detection potentials, posing a significant challenge. To address this issue, this study successfully fabricated a nickel oxide/carbon cloth (NiO/CC) electrode using a one-step electrodeposition method followed by calcination. Taking advantage of the excellent electrocatalytic reduction properties of nickel oxide—particularly the surface oxygen vacancies that serve as active sites for efficient nitrite ion adsorption and promote the hydrogenation of the key intermediate (*NO)—the reaction energy barrier is substantially reduced. As a result, the NiO/CC electrode enables high-sensitivity nitrite detection at a low potential. Electrochemical evaluations reveal that the NiO/CC sensor performs excellently at −0.15 V (vs. Hg/HgO), featuring a linear detection range of 10–500 μM, a low detection limit of 0.091 μM (S/N = 3), and a high sensitivity of 2910 μA·mM⁻¹·cm⁻². These results highlight the promise of a catalytic reduction-based strategy for lowering detection potentials and provide a crucial foundation for the rational design of high-performance electrochemical sensing interfaces. Full article

Low-temperature methanation technology offers a promising pathway for carbon recycling and sustainable energy storage by enabling near-equilibrium CO₂ conversion under atmospheric pressure. However, efficiently activating CO₂ at low temperatures remains a significant challenge due to the kinetic limitations of hydrogenation intermediates. We construct a composite oxide–metal interface structure by anchoring highly dispersed CeCrO_x nanoclusters onto metallic nickel via an ion-exchange method. This catalyst exhibits superior activity compared to conventional Ni/oxide catalysts with identical composition. Under atmospheric pressure at 220 °C, it achieves nearly 80% CO₂ conversion with over 99% methane selectivity and maintains excellent catalytic performance and structural stability during a 240-h continuous test. Systematic characterizations, including high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, CO₂ temperature-programmed desorption, and in situ DRIFTS reflectance infrared Fourier-transform spectroscopy, reveal that the synergistic modification by CeO₂ and Cr₂O₃ not only optimizes the electronic structure of Ni to promote CO₂ adsorption and activation, but also enhances H₂ dissociation and intermediate conversion by regulating oxygen vacancy concentration and alkaline site distribution. Mechanistic studies indicate that the reaction follows a synergistic mechanism dominated by the formate pathway and assisted by the CO pathway. Moreover, the interfacial structure effectively stabilizes active sites and inhibits carbon deposition from CH₄ decomposition. This study provides a universal and effective strategy for designing Ni-based CO₂ conversion catalysts suited for mild reaction conditions and characterized by high energy efficiency. Full article

The oxygen evolution reaction (OER), a key half-reaction in electrochemical water splitting, is limited by sluggish multi-electron transfer kinetics, starting extensive research into efficient, low-cost nanoscale electrocatalysts, particularly those based on nickel, cobalt, and iron, as well as mixed-metal, hybrid, and heteroatom-doped carbon-based metal-free systems, as presented here. Ni- and Co-based electrocatalysts show high efficiency for alkaline OER due to optimized nanostructures, surface modifications, heterostructure design, and multi-metal doping, which enhance activity, stability, and electronic properties. Their performance relies on precise atomic-level control of structure and synergistic interactions, enabling them to approach or rival noble-metal catalysts. Iron-based electrocatalysts are also promising due to their abundance, low cost, and flexible redox chemistry, forming active iron oxyhydroxide species during operation; however, their low conductivity requires structural and electronic optimization. Beyond Fe, Ni, and Co, copper-based compounds, zeolitic imidazolate framework-derived structures, and manganese phosphide–cerium oxide composites offer enhanced oxygen vacancies, tunable structures, and strong interfacial synergy. Furthermore, heteroatom-doped carbon materials incorporating nitrogen, phosphorus, or sulfur improve catalytic activity by modifying electronic structure, creating active sites, and enhancing charge transfer. Overall, careful control of composition, structure, and electronic properties enables the development of efficient, durable, and scalable noble-metal-free catalysts for OER. Full article

Urea electrolysis has emerged as a promising alternative to conventional water electrolysis for hydrogen production, owing to low electrical energy consumption as well as organic wastewater. However, the practical implementation of this approach is primarily constrained by the lack of cost-effective and efficient electrocatalysts. Thus, the development of earth-abundant, non-precious metal-based bifunctional electrocatalysts toward both the hydrogen evolution reaction (HER) and the urea oxidation reaction (UOR) is of critical importance. In this context, nanostructured, reduced nickel-cobalt tungstate supported on Ni foam is fabricated as a binder-free, freestanding electrode via a two-step hydrothermal process followed by partial thermal reduction. By systematically tuning the precursor concentrations of Ni, Co, and W, the morphology and electronic structure of the material are effectively modulated. The introduction of oxygen vacancies through partial thermal reduction plays a key role in enhancing charge transport properties. The optimized NiCo@W_0.5/NF electrode exhibits a porous, flower-like architecture and demonstrates excellent bifunctional electrocatalytic activity toward both UOR and HER, accompanied by improved mass transport behavior. When employed as both the anode and cathode for overall urea electrolysis, NiCo@W_0.5/NF requires a low cell voltage of only 1.68 V to achieve a current density of 100 mA cm⁻² and delivers impressive operational stability in an optimized electrolyte composed of 3 M KOH and 0.33 M urea. These results indicate that NiCo@W_0.5/NF is a highly promising and efficient bifunctional electrode material for urea assisted hydrogen production. Full article

Nickelate oxides show promise for biosensing applications, especially in glucose detection. Creating nickelate-based biosensors involves utilizing their electron-correlated structure and the metal–insulator (MI) transition, which endows them with unique electronic, magnetic, and catalytic properties. Chemical or oxygen vacancies can alter their conductivity and catalytic activity, enabling redox-based detection. In this study, Nd_1−xEu_xNiO₃ films (0 < x < 0.35) functionalized with Glucose Oxidase (GOx) were tested for glucose sensing. Eu substitution shifts the MI transition temperature (T_MI) from 200 K (x = 0) to 340 K (x = 35). At room temperature, these films undergo a metallic-to-insulator phase transition, which, along with the Ni³⁺/Ni²⁺ ratios, influences their sensing capabilities. Time-resolved electrical resistance measurements monitored how glucose interacts with the film surfaces. The sample with x = 0.3 exhibited a measurable resistance change in response to glucose concentrations ranging from 10⁻¹² to 0.5 M, with a sensitivity of 9.1 mM⁻¹ and a limit of detection (LOD) of approximately 0.47 μM. Reproducibility and interference tests with other sugars yielded good results across all samples. Eu doping in NdNiO₃ enhances their sensing response, highlighting the importance of electronic state and MI transition in the sensing performance of these nickelate-based glucose sensors. Full article

Various morphologies of cobalt oxide Co₃O₄ films on cobalt (Co) foils were obtained via anodization followed by a thermal treatment at 350 °C. This study introduces a rapid and cost-effective synthesis route, achieving well-defined spinel structures in only 30 min. The novelty of this work lies in exploring nickel (Ni) as a morphological modifier in the anodization electrolyte. FESEM analysis revealed that, while anodization without Ni produced nanoflake structures, the inclusion of Ni transformed the morphology into larger cubic crystals and rice grain–shaped nanoparticles. XPS confirmed the presence of oxygen vacancies during phase formation, TEM showed spinel grains smaller than 20 nm, and Raman spectroscopy exhibited characteristic peak shifts influenced by both anodization and Ni addition. These results demonstrate that Ni not only accelerates the formation of spinel $\mathrm{C}{\mathrm{o}}_3{\mathrm{O}}_4$ but also plays a decisive role in tailoring morphology, highlighting the efficiency and novelty of this approach. Full article

Aqueous zinc-ion batteries (AZIBs) have gained significant attention as promising candidates for next-generation energy storage systems, especially in mobile robotics, due to their inherent safety, environmental friendliness, and low cost. However, the practical application of AZIBs is often hindered by slow Zn²⁺ diffusion and the poor structural stability of the cathode materials under high-rate or long-term operation. To address these challenges, a defect-engineered, binder-free MnO₂ electrode, with a MnO₂ loading of 1.35 mg·cm⁻², is synthesized via in situ hydrothermal growth of ultrathin MnO₂ nanosheets directly on a 3D conductive nickel foam scaffold, followed by reductive annealing to introduce abundant oxygen vacancies. These oxygen-rich defect sites significantly enhance Zn²⁺ adsorption, improve charge transfer kinetics, and contribute to enhanced pseudocapacitive behavior, further improving overall electrochemical performance. The intimate contact between the MnO₂ and Ni substrate ensures efficient electron transport and robust structural integrity during repeated cycling. With this synergistic architecture, the MnO₂@Ni electrode achieves a high specific capacity of 122.9 mAh·g⁻¹ at 1 A·g⁻¹, demonstrating excellent cycling durability with 94.24% capacity retention after 800 cycles and nearly 99% coulombic efficiency. This study offers a scalable strategy for designing high-performance, structurally stable Zn-ion battery cathodes with improved rate capability, making it a promising candidate for energy-intensive mobile robotic and flexible electronic systems. Full article

Thin films of manganese–nickel–cobalt oxide with graphene (G@MNCO) were deposited on copper foam using electrochemical deposition. NiCo₂O₄ is the main phase in these films. As the proportion of graphene in the precursor solution increases, the oxygen vacancies in the samples also increase. The microstructure of these samples evolves into hierarchical vertical flake structures. Cyclic voltammetry measurements conducted within the potential range of 0–1.2 V reveal that the electrode with the highest graphene content achieves the highest specific capacitance, approximately 475 F/g. Furthermore, it exhibits excellent cycling durability, maintaining 95.0% of its initial capacitance after 10,000 cycles. The superior electrochemical performance of the graphene-enhanced, manganese-doped nickel–cobalt oxide electrode is attributed to the synergistic contributions of the hierarchical G@MNCO structure, the three-dimensional Cu foam current collector, and the binder-free fabrication process. These features promote quicker electrolyte ion diffusion into the electrode material and ensure robust adhesion of the active materials to the current collector. Full article

The oxygen evolution reaction (OER) is pivotal in hydrogen production via water electrolysis, yet its sluggish kinetics, stemming from the four-electron transfer process, remain a major obstacle, with overpotential reduction being critical for enhancing efficiency. This work addresses this challenge by developing a novel approach to stabilize and activate non-precious metal catalysts for OER. Specifically, we synthesized a three-dimensional flake NiFe-LDH/ZIF-L composite catalyst on a flexible nickel foam (NF) substrate through a room temperature soaking and hydrothermal method, leveraging the mesoporous structure of ZIF-L to increase the specific surface area and optimizing electron transfer pathways via interfacial regulation. Continuous linear sweep voltammetry (LSV) scanning induced structural self-reconstruction, forming highly active NiOOH species enriched with oxygen vacancies, which significantly boosted catalytic performance. Experimental results demonstrate an overpotential of only 221 mV at 10 mA cm⁻² and a Tafel slope of 56.3 mV dec⁻¹, alongside remarkable stability, attributed to the catalyst’s hierarchical nanostructure that accelerates mass diffusion and charge transfer. The innovation lies in the synergistic effect of the mesoporous ZIF-L structure and interfacial regulation, which collectively enhance the catalyst’s activity and durability, offering a promising strategy for advancing large-scale water electrolysis hydrogen production technology. Full article