ABSTRACT Achieving acid‐like hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) activity in alkaline media using low‐cost, non‐precious metal catalysts is essential for energy conversion technologies. Here, we demonstrate the indispensable role of water within the catalyst layer in enhancing HOR/HER kinetics, mediated by hydrated and dehydrated oxophilic sites on nickel (Ni) catalysts coated with nickel hydroxide (Ni(OH) 2 ). Electrochemical measurements combined with density functional theory (DFT) calculations show that an acid‐like environment creates at the electrified interface through water molecules that bridge active hydrogen and oxygen species within the catalyst surface layer. This interfacial behavior differs from that described in conventional bulk and interface models. Our findings highlight the importance of interfacial hydrogen bonding network across the interface in hydrogen electrocatalysis and provide guidance for the design of efficient catalysts for alkaline fuel cell and electrolyzer applications.

Coupling oxygen vacancies-enriched nickel hydroxides with copper nanowires for tandem electrocatalysis in electrochemical nitrate reduction to ammonia

Novel casein-infused nickel hydroxide bio-nanocomposite: Synthesis and analysis of electrochemical and antimicrobial behaviour

Regulating polysulfide conversion and Lithium deposition by hetero-interfacing enable multifunctional separator for highly efficient Lithium-sulfur batteries.

ABSTRACT This study investigates the effect of manganese (Mn) doping (1–5 wt. %) on the phase transition of nickel hydroxide (Ni(OH) 2 ) to nickel oxide nanoparticles (NiO NPs) synthesized via a green route. Phase transition, structural, optical, and magnetic properties of Mn‐doped NiO are thoroughly investigated. Thermogravimetric analysis (TGA) reveals the influence of Mn on the thermal decomposition and the stability of Ni(OH) 2 and the organic compounds from olive leaf extract under inert calcination conditions. X‐ray photoelectron spectroscopy (XPS) provides insights into surface chemistry modifications before and after calcination, as well as in the presence of Mn. X‐ray diffraction (XRD) confirms Mn incorporation and lattice distortion within the NiO structure. HRTEM and BET analyses show that 2 wt. % Mn is a critical concentration, yielding the smallest spherical particle size (6 nm) and the highest surface area. The calculated work function from ultraviolet photoelectron spectroscopy (UPS) reveals a decrease from 6.0 eV (0 wt. % Mn) to 5.4 eV (5 wt. % Mn). Analysis of the valence band maximum (VBM) region further indicates a bandgap widening with Mn incorporation. Raman spectra reveal the appearance of the two magnon (2M) vibrational mode, suggesting modified magnetic behavior. Vibrating sample magnetometry (VSM) indicates a ferromagnetic response, with the appearance of a Néel temperature at 5 wt. % Mn, indicating an antiferromagnetic to paramagnetic transition. This study offers key insights into the design of stable, high‐performance materials for photovoltaic and magnetic applications.

The development of advanced carbon anodes is pivotal for enabling high-performance sodium-ion batteries (SIBs). However, their reaction dynamics and cycling stability remain a formidable challenge. In this work, we report a novel three-dimensional (3D) carbon framework anode (S-CNS@CNF), featuring engineered carbon nanosheet arrays coupled with a sulfur and nitrogen codoping strategy. Specifically, nickel hydroxide is employed as a structural inducer to facilitate the vertical anchoring of carbon nanosheet arrays onto porous carbon nanofibers, thereby constructing an interconnected 3D porous architecture. This hierarchical structure affords a wealth of active sites for Na+ adsorption while simultaneously facilitating highly efficient pathways for electron transport. Furthermore, N, S codoping introduces a high density of defect sites and enlarges the interlayer spacing of the carbon nanosheets. Experimental findings combined with theoretical calculations reveal that the incorporation of sulfur into the carbon further enhances the Na+ storage kinetics and increases Na+ adsorption energy. Benefiting from the synergistic effects between interconnected 3D porous architectures and N, S doping, the as-prepared anode delivers a high reversible capacity of 399.5 mAh g-1 at 0.1 A g-1 and outstanding rate capability, retaining 146.7 mAh g-1 at 20 A g-1. When Na3V2(PO4)3 (NVP) is employed as the cathode, the NVP//S-CNS@CNF full cell outputs a specific capacity of 117.6 mAh g-1 at 2 A g-1.

Nickel hydroxide is a commonly used anode material for supercapacitors, offering advantages such as high theoretical capacity and abundant raw material availability. However, it also faces challenges, including low electrical conductivity and limited cycling stability. In this work, a heterostructure composed of NixCo1-x(OH)2 layered material with cobalt-substituted nickel sites and reduced graphene oxide (rGO) was constructed via a one-step hydrothermal approach, and the interlayer anions were further modulated to elevate the entire electrochemical efficacy of the resulting material. Herein, the tetraborate ions (B4O72-) with electron-unsaturated characteristics are utilized to bond with the hydroxyl groups within the nickel hydroxide layer, thereby generating a robust pillar effect that enhances the reaction kinetics and improves the stability of the layered structure. Simultaneously, partial substitution of the nickel active site by cobalt facilitates the formation of a more stable layered hydroxide structure, reducing microstructural collapse following proton intercalation and deintercalation. Additionally, the incorporation of rGO provides more active sites for material growth and leads to an enhancement in electron transport efficiency. The electrochemical properties of the as-prepared Ni9Co-TB/G0.03 composites were markedly enhanced. The specific capacitance reached 1977 F·g-1 under 1 A·g-1, and the capacity retention rate stayed at 88% following 5000 cycles performed at 10 A·g-1. An asymmetric supercapacitor, Ni9Co-TB/G0.03(+)||AC(-), was constructed with a commercial activated carbon negative electrode, with energy density maximization as the evaluation criterion. The device exhibited a specific capacitance of 164 F·g-1Total at 1 A·g-1Positive. At an elevated current density of 80 A·g-1Positive, 100 F·g-1Total of specific capacitance was retained, equivalent to 61% capacitance retention. This demonstrated excellent rate capability and outstanding overall performance, simultaneously delivering 44 Wh·kg-1 energy density and 16,687 W·kg-1 power density.

Diclofenac electrooxidation at nickel hydroxide and its analytical application

Boosting acetylcholine electrochemical detection through synergistic oxygen and nickel vacancies in nickel hydroxide

Influence of atomic layer deposition on nickel hydroxide phase transitions in nickel foam

Taking lithium manganese iron phosphate (LMF) as the research object, surface modification was used to carry out the modification research on it, and the effects of the Ni coating method, different precipitating agents and different coating amounts on the electrochemical performance of LMF cathode materials were investigated. The effects of different precipitants (nickel oxalate and nickel hydroxide) and nickel coating amounts on the electrochemical performance of lithium manganese iron phosphate materials were investigated, and the optimal coating conditions were determined. The optimum cladding conditions are: nickel sulphate and sodium hydroxide as precipitant cladding 1% nickel. The discharge capacity at 0.2C magnification was 150.9 mAh-g-1, and the retention of discharge specific capacity after 100 cycles was 95% (0.5C), 92.6% (1C) and 86.9% (2C), respectively.

A reliable determination of the atomic and electronic structure of nickel (oxy)hydroxide (NiOOH) is crucial for understanding its application as an oxygen evolution reaction (OER) electrocatalyst. However, discrepancies across experimental and computational studies have left the structure-composition-activity relationship of β-NiOOH poorly defined. In this work, we reassess the atomic and electronic structure of β-NiOOH using first-principles density functional theory calculations, emphasizing the influence of exchange-correlation functional and choice of ground-state structure on predicted structural and electronic properties. Simulated Raman is employed as an additional validation metric to inform structural assignments. Building on the optimized bulk β-NiOOH model, we construct and analyze a Fe-doped β-NiFeOOH (001) surface to explore the electronic and catalytic consequences of 25% Fe incorporation. Our comparative computational framework enables consistent evaluation of bulk and surface properties, offering deeper insights into the role of structural motifs in governing OER activity and guiding the design of improved earth-abundant electrocatalysts.

This work reports the electrochemical behavior of a nickel hydroxide electrode, electrodeposited in a deep eutectic solvent (DES), in alkaline solutions of varying composition, aiming to elucidate the influence of the cation (Na+ vs. K+), urea, and carbonate ions on the mechanism and kinetics of anodic processes. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to analyze the electrochemical responses of electrode processes in alkaline water electrolysis systems. For the urea oxidation reaction (UOR), the frequency-dependent characteristics were thoroughly characterized, and the impedance response was simulated according to the Armstrong–Henderson equivalent circuit. It was found that the addition of urea significantly transforms the impedance structure, sharply reducing the polarization resistance and increasing the pseudo-capacitive component of the constant phase element at low frequencies, indicating activation of the slow steps of urea oxidation via a direct mechanism and the formation of an extended adsorptive surface. It was demonstrated that, unlike conventional alkaline electrolysis where KOH-based systems are generally more effective, urea-assisted systems exhibit superior performance in NaOH-based electrolytes, which provides more favorable kinetics for the electrocatalytic urea oxidation process. Furthermore, the accumulation of carbonate ions was shown to negatively affect UOR kinetics by increasing polarization resistance and partially blocking surface sites, highlighting the necessity of controlling electrolyte composition in practical systems. These findings open new opportunities for the rational design of efficient urea-assisted electrolyzers for green hydrogen generation.

Nickel (II) hydroxide (Ni(OH)₂) nanoparticles have attracted significant research interest due to their potential in applications such as supercapacitors, batteries, and electrocatalysis. However, conventional synthesis methods often face challenges related to high costs and complex instrumentation. This study presents a simple, low-cost, and controllable approach for synthesizing Ni(OH)₂ nanoparticles using a surfactant-assisted electrochemical method. The synthesis was conducted through electrolysis at 100°C in an aqueous solution containing sodium citrate, with Tween 20 employed as a structure-directing agent, Tween 20 was effective in producing smaller, dispersed, quasi-spherical particles while preventing severe agglomeration. The resulting nanoparticles were characterized using various analytical techniques, including UV-Vis and FTIR spectroscopy, X-ray Diffraction (XRD), Thermal Gravimetric Analysis (TGA), and electron microscopy (TEM/SEM). UV-Vis analysis showed a characteristic absorption peak at 387 nm, confirming nanoparticle formation. XRD analysis validated the synthesis of a nanocrystalline hexagonal Ni(OH)₂ phase. Electron microscopy revealed a hierarchical, flower-like morphology composed of nanosheets and demonstrated that Tween 20 was effective in producing smaller, dispersed, quasi-spherical particles while preventing severe agglomeration. Furthermore, the thermal decomposition of Ni(OH)₂ into highly crystalline cubic, NiO via calcination was confirmed by TGA, XRD, and FTIR analyses, with the main decomposition occurring at approximately 335°C. This research demonstrates an effective and economical route for producing Ni(OH)₂ nanoparticles with controlled morphology, enhancing their potential for practical applications.

Electrolysis of seawater is considered a green route for hydrogen generation; however, its practical application is limited by strong electrode corrosion and slow OER kinetics in chloride-rich media. Herein, we report a crystal-facet engineering strategy to construct nickel hydroxide with a parallel array structure on nickel foil (denoted as Ni(OH)2/NFPA, where NFPA represents nickel foil with parallel array) via a facile two-step etching-hydrothermal method. Structural characterization confirms the formation of high-index Ni(220) surfaces and well-aligned hydroxide nanostripes, which promote more favorable bubble–electrode interactions and contribute to improved interfacial stability. Owing to its characteristic parallel array configuration, Ni(OH)2/NFPA exhibits outstanding OER performance in alkaline electrolyte, delivering a low overpotential of 256 mV at 10 mA·cm−2 together with a Tafel slope as small as 74.9 mV·dec−1, surpassing commercial RuO2 and disordered Ni(OH)2 nanosheets. The optimized electrode also delivers remarkable durability, maintaining stable operation for 48 h at 100 mA·cm−2 even under harsh alkaline seawater conditions at 80 °C. Bubble dynamics analysis reveals that the ordered array morphology produces a superaerophobic surface, enabling rapid detachment of oxygen bubbles and ensuring efficient mass transport. This study highlights facet-controlled construction of parallel nanoarrays as a promising approach to improve catalytic efficiency, corrosion resistance, and bubble management in seawater electrolysis, offering useful implications for the rational design of high-performance electrodes for practical hydrogen production.

In nature, hollow precipitation tubes form around deep sea hydrothermal vents and generate an electric potential across the material membrane. These structures are of significant scientific interest due to their possible connection to the origins of life on Earth, and synthetic precipitation membrane structures have been created in the laboratory to study their growth. This paper reports on the formation of metal hydroxide precipitation membranes within a microfluidic device designed to allow for the measurement of the electric potential across the flow channel during material formation. Using this device, the electric potential and growth curves were measured for nickel hydroxide, iron hydroxide, and cobalt hydroxide precipitation membranes. Based on these experiments, it was hypothesized that the application of an electric potential in opposition to the generated potential would reduce the growth rate of the membranes, and this hypothesis was experimentally verified. The results of this work discuss that the membranes formed are likely selectively permeable to a diffusive positive ion, possibly H+, which is responsible for controlling the growth rates of the material. Additional experiments, including direct electrical measurements of the membrane itself during growth, measurement of the pH within the flow channel, and material characterization after removal from the device, are proposed to further explore the growth of precipitation membranes.

Mn species-induced high-efficiency nickel hydroxide electrocatalyst for co-production of 2,5-furandicarboxylic acid and hydrogen

Enhanced electrocatalytic oxidation of 5-HMF to FDCA using cobalt-doped nickel hydroxide: Broadening the potential window and improving efficiency

Composites made of lotus-seedpod-derived carbon and nickel hydroxide sulfate nanofibers: Advanced materials for supercapacitor electrodes

The electrochemical reduction of CO2 (CO2RR) offers a promising route for sustainable fuel and chemical production. This study compares the CO2RR performance of hydrothermally synthesized carbon nanosphere-supported nickel hydroxide (Ni–C), copper hydroxide (Cu–C), and bimetallic nickel–copper hydroxide (NiCu–C) catalysts, investigating the influence of metal composition. Significant differences in product selectivity were observed: Cu–C primarily yielded C2 products, whereas Ni–C and NiCu–C generated mixtures of H2, CO, formate, and acetate, with minimal C3 products. Faradaic efficiencies (FEs) for C3 products (including propylene, propane, and n-propanol) were very low for Ni–C and NiCu–C (<0.3% combined). In comparison, Cu–C showed modest FEs (∼3–5%) primarily for n-propanol. X-ray photoelectron spectroscopy revealed partially oxidized nickel species (Niδ+) in Ni–C and NiCu–C and predominantly Cu(i) species post-reaction, while scanning electron microscopy confirmed a distinct fibrous morphology for the Ni-containing catalysts. Control experiments with CO and acetate, and in situ Raman spectroscopy, suggest reaction pathways that differ from the typical Cu-catalyzed routes, potentially involving hydrogenated intermediates such as *CHO. This work provides a comparative analysis, highlighting how catalyst composition and associated electronic/structural properties influence the overall CO2RR activity and selectivity pathways in Ni, Cu, and NiCu hydroxide systems, rather than achieving significant C3 production.