Search Results (589)

Achieving the coexistence of high energy density and fast-charging capability remains a fundamental challenge for lithium-ion batteries. Increasing electrode thickness and compaction density enhances energy density but simultaneously alters the pore structure and restricts lithium-ion transport, leading to concentration polarization, increased resistance, and lithium plating. In this work, we employ X-ray computed tomography (X-CT) and 3D reconstruction to establish quantitative relationships between particle size, compaction density, and key structural parameters (porosity, tortuosity, effective proportion of lithium-ion flux (f_eff)). Then, an electrochemical model is used to link the liquid-phase kinetic parameters (ionic conductivity (k₀) and liquid-phase diffusion coefficient), as corrected by the effective proportion of lithium-ion flux f_eff, to polarization and lithium-plating behavior, and the maximum current density without lithium plating under various fabrication conditions is finally determined. Results show that small-particle electrodes exhibit superior rate capability at moderate compaction levels, but suffer from rapidly increasing tortuosity and reduced transport efficiency under high compaction and large thickness. Moreover, a double-layer gradient electrode design effectively integrates the advantages of both large- and small-particle architectures, enabling high-rate operation without lithium plating. The double-layer gradient electrode (ρ = 1.6 g/cm³) exhibited ~50% higher performance at 1.5 C compared to the small-particle anode and enabled 2 C charging without lithium plating. This study offers a robust structural design strategy for optimizing thick-electrode architectures toward high-energy, fast-charging LIBs. Full article

High-liquid-limit clay exhibits pronounced water sensitivity due to the strong electrostatic repulsion and weak interparticle bonding within its microstructure, which often limits its direct engineering uses and complicates the reuse of excavated clayey soils generated during the construction of transportation infrastructure. In this study, inorganic salts (KCl, CaCl₂ and FeCl₃) and carboxyl-containing polymers (PAAS, HPMA and CMC) were screened to construct organic–inorganic composite stabilization systems. Based on the screening results, an organic–inorganic composite system composed of CaCl₂ and sodium polyacrylate (PAAS) was developed to regulate interfacial interactions and induce microstructural reconstruction in clay. The synergistic mechanisms governing particle aggregation and dispersion were systematically investigated through Atterberg limit tests, zeta potential measurements, DLVO theoretical calculations, particle size analysis, scanning electron microscopy (SEM) and immersion disintegration experiments, combined with multivariate statistical modeling. Among the tested salt–polymer formulations, a composite system with 2% CaCl₂ and 0.1% PAAS showed the most favorable overall performance, achieving an optimal balance between electrostatic compression and steric stabilization, leading to enhanced structural integrity and delayed water-induced disintegration. Ca²⁺ ions compress the diffuse double layer and promote particle flocculation, whereas adsorbed PAAS chains introduce steric hindrance and interfacial modification. Their synergistic interaction reconstructs the pore–aggregate framework and regulates the interparticle potential energy landscape. DLVO analysis indicates that the optimized system attains a moderate critical interaction distance (h_c = 7.31 nm) and primary minimum depth (DPM = −2.72 × 10⁻¹⁶ J), reflecting a balanced interfacial bonding state. Multivariate statistical analyses further reveal a dual control pathway, in which consistency primarily governs disintegration duration, with additional contributions from surface electrochemical properties, while surface properties, soil structure and consistency collectively influence disintegration initiation. These findings elucidate the interfacial regulation and structural evolution mechanisms in organic–inorganic composite systems and provide insights into the design of composite modifiers for water-sensitive particulate materials, particularly for the resource reuse of high-liquid-limit clay excavated during the construction of transportation infrastructure and related geotechnical engineering applications. Full article

The increasing accumulation of poly(ethylene terephthalate) (PET) waste poses a significant environmental challenge and highlights the need for sustainable, value-added recycling strategies. In this study, porous carbon derived from PET was synthesized via carbonization and chemical activation and subsequently combined with manganese dioxide (MnO₂) to fabricate hybrid electrodes for aqueous supercapacitors. The PET-derived carbon exhibits a highly microporous structure with a large specific surface area and functions as a conductive and mechanically stable matrix that improves MnO₂ dispersion, charge transport, and electrochemical utilization. Systematic electrochemical investigations reveal strongly electrolyte-dependent charge-storage behavior. In an alkaline electrolyte, the capacitance is dominated by MnO₂ pseudocapacitive redox reactions, whereas in a neutral electrolyte, the response is primarily governed by electric double-layer charge storage. In a ferricyanide-containing redox-active electrolyte, additional electrolyte-mediated faradaic processes significantly enhance the apparent electrochemical performance. Under these conditions, the hybrid electrodes deliver a high apparent specific capacitance of 240–250 F g⁻¹ at moderate current densities. The electrodes further demonstrate stable cycling behavior and high apparent Coulombic efficiency, reflecting time-dependent utilization of both MnO₂ pseudocapacitance and redox-active electrolyte species during charge–discharge. Crucially, this work demonstrates that PET-derived carbon/MnO₂ hybrid electrodes exhibit complex, electrolyte-controlled charge-storage mechanisms and underscores the critical role of electrolyte selection in accurately interpreting electrochemical metrics and optimizing the performance of sustainable supercapacitors based on recycled polymer-derived carbons. Full article

The electrochemical behavior of metallic rhenium was investigated using voltammetry and ex situ X-ray photoelectron spectroscopy (XPS) in aqueous acidic methanol solutions. Capacitance–potential analysis revealed that the double-layer current is governed by an adsorption–desorption surface process involving oxygen and sulfate species, as confirmed by XPS. The hydrogen evolution reaction (HER) proceeds via a Volmer–Heyrovsky mechanism, with hydrogen adatoms, physisorbed oxygen, and chemisorbed sulfate molecules as key intermediates. Methanol does not inhibit hydrogen gas production, and oxygenated species actively participate in the HER pathway. Voltammetric measurements demonstrated that rhenium cathodes are highly efficient for methanol electrolysis in membraneless systems, suggesting their potential application in electrolysis processes involving unpurified wastewater. These findings highlight rhenium as a promising electrode material for use in sustainable energy conversion technologies. Full article

This study reports a straightforward and controllable two-step hydrothermal synthesis of novel Ni₉S₈@NiMoO₄/NF nanospherical catalysts supported on nickel foam (NF), accompanied by a systematic evaluation of their performance in the electrochemical hydrogen evolution reaction (HER). Structural characterization revealed a well-defined Ni₉S₈–NiMoO₄ interfacial region, whose synergistic interaction, combined with the distinctive nanospherical morphology, substantially increased the electrochemically active surface area and the density of reactive sites, thereby optimizing HER kinetics. In alkaline media, the Ni₉S₈@NiMoO₄/NF catalyst demonstrated outstanding electrocatalytic performance, delivering an overpotential of only 64.2 mV at a current density of 20 mA cm⁻². The catalyst also exhibited a high double-layer capacitance of 22.2 mF cm⁻², reflecting a substantial active interfacial area. Long-term durability tests showed negligible performance degradation after 165 h of continuous operation at 10 mA cm⁻², underscoring the catalyst’s robust structural stability and durability. X-ray photoelectron spectroscopy confirmed a uniform distribution of Ni, Mo, and S across the NF framework and revealed optimized chemical states, providing material-level evidence for the enhanced performance. Collectively, this work proposes a viable strategy for designing efficient and stable HER catalysts, contributing to the advancement of green hydrogen production and clean energy technologies. Full article

Layered double hydroxides (LDH) demonstrate significant potential in flexible superca-pacitors due to their high energy storage capability and adjustable architectures. Never-theless, the practical specific capacitance exhibited by current LDH remains below expec-tations, which is attributed to suboptimal electrode performance and limited active sites. Herein, a novel Fe-doped NiFeCo-LDH/NiFeCoO nanosheet composite supported on car-bon cloth was designed and fabricated as a flexible electrode. In this composite, the Ni-FeCo-LDH supplies numerous reactive centers and accelerates electrochemical kinetics, while the NiFeCoO and carbon cloth significantly improve electrical conductivity and cy-cling stability. Moreover, the heterointerface formed between the LDH and the metal oxide phase further facilitates charge transfer. Owing to such synergistic interactions, the pre-pared NiFeCo-LDH/NiFeCoO@CC electrode demonstrates an excellent areal specific ca-pacitance of 3.282 F cm⁻² at a current density of 1 mA cm⁻², while maintaining a high ca-pacity preservation reaching 88.09% following 5000 cycles. Furthermore, the assembled NiFeCo-LDH/NiFeCoO@CC//AC asymmetric supercapacitor delivers an outstanding en-ergy density reaching 0.302 mWh cm⁻² under a power density of 0.776 mW cm⁻², coupled with an excellent capacitance preservation of 85.29% over 5000 cycles. Meanwhile, it can maintain its initial capacitance under varying bending degrees, rendering it widely ap-plicable for future advanced flexible and wearable electronic devices. Full article

A corrosion device was established to simulate the service environment of stainless steel heat exchanger tubes in a gas water heater. The pitting corrosion behaviors on the inner walls of 444, 445 and 316L stainless steel tubes were investigated in a tap water solution at 60 °C under different heating temperatures from 600 to 800 °C for 500 h by means of optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The increase in heating temperature significantly promotes the thickening of scale layers and the formation and growth of corrosion pits on the inner surfaces of the three stainless steel tubes. Under different heating temperature conditions, the maximum and average depths of corrosion pits decrease sequentially from 444 to 445 and then to 316L stainless steel. The scales have similar compositions for the three steel tubes, but the scale thickness is thinner on 316L stainless steel than on the other two steels. In addition, the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test indicates that there is almost no sensitization for the outer walls of the three stainless steel tubes after being heated at 800 °C. Full article

Despite the long-standing recognition of nickel as an effective electrocatalyst for the alkaline hydrogen evolution reaction (HER), the majority of extant studies primarily focus on initial catalytic performance or short-term stability under relatively low current densities. In practical alkaline water electrolysis, however, electrodes operate continuously at elevated current densities for extended periods, where surface chemical states and electrochemical responses may evolve dynamically. A systematic understanding of such time-dependent behaviour remains limited, particularly for electrodeposited nickel under sustained operation. In this study, the long-term HER performance of electrodeposited Ni electrodes at a current density of 100 mA cm⁻² over 120 h is investigated. The objective of this study is to correlate the evolution of electrochemical performance with changes in surface chemical states during prolonged electrolysis. To this end, a combination of methods was employed, including polarization measurements, electrochemical impedance analysis, double-layer capacitance evaluation, and ex situ surface characterization. In contrast to the tendency to prioritize absolute enhancement of activity, this study places greater emphasis on the transient decline–recovery–stabilization behaviour that is observed during operation. Furthermore, it discusses the potential relationship of this behaviour with surface hydroxylation and restructuring processes. The present study utilizes a time-resolved analysis to elucidate the dynamic surface evolution of nickel electrodes under practical alkaline HER conditions, thereby underscoring the significance of evaluating catalyst durability beyond the confines of short-term measurements. The findings presented herein contribute to a more realistic assessment of nickel-based electrodes for alkaline water electrolysis applications. Full article

Cobalt disulfide (CoS₂) features highly active catalytic sites and is regarded as a promising candidate for electrocatalytic hydrogen evolution. In this study, molybdenum-doped cobalt disulfide (CoS₂:Mo) was synthesized via a facile hydrothermal approach. XRD analysis confirms that the obtained samples crystallize in a cubic pyrite structure, with diffraction peaks consistently shifting towards lower angles. SEM characterization reveals that the samples exhibit microrod-like morphologies with an average size of approximately 1 μm. Integrated analyses from XRD, XPS, and EDS mapping demonstrate that Mo is uniformly distributed across the surface and successfully doped into the CoS₂ lattice. Electrochemical measurements indicate that the CoS₂:Mo sample delivers a low overpotential of 122 mV and a Tafel slope of 128 mV dec⁻¹ at a current density of 10 mA cm⁻² in alkaline media, significantly surpassing the performance of pure CoS₂ and MoS₂. Moreover, the CoS₂:Mo exhibits an enhanced double-layer capacitance, with a C_dl value of 2.72 mF cm⁻², superior to that of pure CoS₂ (1.63 mF cm⁻²) and MoS₂ (0.31 mF cm⁻²). Mo doping enhances conductivity and active sites, thereby boosting electrocatalysis. This work presents an effective strategy for the development of cost-efficient and high-performance non-precious metal electrocatalysts. Full article

This study aims to investigate the potential for using commercial building materials such as cement and quarry sand for developing functional building components with electrical energy storage capacities. Cubic specimens of cement mortars made from commercial Portland cement and quarry sand were fabricated, while commercial galvanized mesh, used for mortar reinforcement, was used as electrodes. Moreover, natural zeolites were used as additives to modify mortar electrical properties. Cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to assess the capacity of the fabricated specimens for electrical energy storage. Results indicated that the studied cement mortars modified with natural zeolites behave as a non-ideal electrical double-layer capacitor (EDLC) with stable capacitive behavior over time. This makes these cementitious materials promising for further research in electrical energy storage applications. Full article

Growing interest in sustainable, high-performance energy storage has driven extensive studies on advanced electrode materials for supercapacitor applications. In this study, a FeNiCo metal–organic framework/multiwalled carbon nanotube (MOF–MWCNT) composite was synthesized and employed as a modifying layer on a carbon felt electrode (CFE) via a drop-casting method. The electrochemical performance of the composite electrode was systematically evaluated in 1 M H₂SO₄ electrolyte. Structural and electrochemical studies demonstrate that the combined effect of the conductive CFE substrate, the electric double-layer capacitance of MWCNTs, and the pseudocapacitive properties of the trimetallic FeNiCo MOF markedly enhances the charge storage performance. Cyclic voltammetry and galvanostatic charge–discharge measurements demonstrate a maximum specific capacitance of approximately 180 F g⁻¹. The electrode delivers an energy density of 73.20 Wh kg⁻¹ at a power density of 3796.17 W kg⁻¹, demonstrating a favorable balance between energy and power performance. In addition, high coulombic efficiency confirms excellent charge–discharge reversibility. Notably, 71% of the initial capacitance is retained after 900 cycles in 1 M H₂SO₄, indicating stable electrochemical behavior even under strongly acidic conditions. These findings emphasize the promise of the FeNiCo MOF–MWCNT/CFE composite as a durable electrode design for next-generation supercapacitor devices. Full article

The characterization of supercapacitors (SCs), particularly electric double-layer capacitors (EDLCs), is useful for the design of energy management systems. This article presents a five-parameter dynamic model based on electrochemical impedance spectroscopy (EIS) data. Unlike conventional fixed-parameter models, this study explores an approach that accounts for voltage dependence. The model was evaluated using four commercial 58-farad SCs over a frequency range of 10 mHz to 300 kHz and at voltages ranging from 6.25% to 93.75% of the nominal value. The results show that the parameters vary with the state of charge; for example, the effective capacitance increased by up to 24% when moving from 6.25% to 50% of the nominal voltage. The model, fitted using nonlinear optimization algorithms, has a mean square percentage error (MSPE) of less than 3%. This approach estimates the dynamic behavior of the SCs, facilitating the simulation and tuning of management and protection strategies. Full article

Molecularly imprinted polymers (MIPs) are widely employed for selective adsorption of target molecules in sensing and separation applications. The architecture of MIP films can influence adsorption behavior, interfacial stability, and reusability, yet systematic investigations of these effects are limited. This study aimed to evaluate how different polypyrrole (PPy) MIP film architectures affect the adsorption, stability, and regeneration characteristics of geraniol-imprinted layers on gold electrodes. Geraniol-imprinted and non-imprinted PPy films were electropolymerized onto quartz crystal microbalance (QCM) substrates. Two film architectures were compared: (i) a single-layer geraniol-imprinted PPy film, and (ii) a double-layer film consisting of a non-imprinted PPy underlayer followed by a geraniol-imprinted layer. Film characterization was performed using cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) measurements. Adsorption–desorption cycles were conducted to assess mass uptake, signal stability, and regeneration performance. EQCM analysis revealed that the double-layer architecture exhibited enhanced frequency signal stability during repeated adsorption–desorption cycles compared to single-layer films, suggesting a stabilizing effect of the underlying non-imprinted PPy layer at the electrode interface. Geraniol-imprinted films demonstrated significantly higher mass uptake than non-imprinted controls, confirming the sensitivity provided by molecular imprinting. Single-layer films showed more variability in signal response and less consistent regeneration performance. The architecture of MIP films significantly affects adsorption behavior, stability, and regeneration on electrode surfaces. Incorporating a non-imprinted PPy underlayer can improve signal reproducibility and enhance the robustness of MIP-based sensing interfaces. These findings provide guidance for the rational design of MIP coatings for electrochemical sensors and QCM-active platforms. Full article

Layered nickel-rich cathodes are regarded as promising cathode materials for lithium-ion batteries (LIBs) due to their higher electrochemical capacities and lower cost. However, the development and commercial application of nickel-rich cathodes are severely hindered by significant capacity fading under a high charge cut-off voltage (4.5 V), which arises from interfacial instability and bulk structural degradation during charge–discharge processes. In this study, a two-step double-coating strategy was innovatively adopted to successfully synthesize Al₂O₃/LiBO₂ co-coated LiNi_0.71Co_0.09Mn_0.2O₂ cathode material (denoted as NCM-Al/B). X-ray photoelectron spectroscopy (XPS) verified that Al existed stably in the form of Al³⁺, and B formed B-O-M covalent bonds with transition metals (Ni/Co/Mn), constructing a dual-element synergistic interface. This interface significantly reduced the surface Ni³⁺ content and enhanced the structural stability by suppressing the H₂→H₃ phase transition. The NCM-Al/B material exhibits excellent electrochemical performance: it maintains a remarkable cycling stability with a capacity retention of 91.6% after 100 cycles at 1 C and 25 °C and delivers a discharge capacity of 156.6 mAh·g⁻¹ with a capacity retention of 75.4% after 100 cycles at a high rate of 1 C. This work establishes a chemically driven double-coating strategy and provides a new paradigm for optimizing the performance of high-nickel cathode materials. Full article

Organic coatings are used as one of the most effective strategies for the corrosion protection of metals. Nowadays, due to environmental regulations, the use of water-based coatings has become essential compared to solvent-based ones. However, their application to magnesium alloys remains largely unexplored due to their high reactivity with water. In the present work, a phosphate-functionalized waterborne binder is applied to AZ31B magnesium alloy. The surface has been modified by four different pre-treatments, respectively: (i) mechanical grinding, (ii) pickling, (iii) conventional conversion treatment, and (iv) a novel conversion treatment based on layered double hydroxides (LDH). The most promising pre-treatments are selected to explore their synergy with a biobased waterborne binder, containing CeO₂ nanoparticles as a corrosion inhibitor. The morphology and composition of the different systems are studied, prior to and after corrosion tests in NaCl solution, by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Results obtained by electrochemical impedance spectroscopy (EIS) in NaCl solution have revealed not only that LDH performs better than the conventional conversion treatment but also the synergy between LDH pre-treatment and CeO₂ nanoparticles when two organic layers are used. Full article