Search Results (928)

The complex system of high-entropy materials makes it challenging to reveal the specific function of each site for oxygen evolution reaction (OER). Here, with nickel foam (NF) as the substrate, FeCoNiCrMo/NF is designed to be prepared by metal–organic frameworks (MOF) as a precursor under an argon atmosphere. XRD analysis confirms that it retains a partial MOF crystal structure (characteristic peak at 2θ = 11.8°) with amorphous carbon (peaks at 22° and 48°). SEM-EDS mapping and XPS demonstrate uniform distribution of Fe, Co, Ni, Cr, and Mo with a molar ratio of 27:24:30:11:9. Electrochemical test results show that FeCoNiCrMo/NF has excellent OER characteristics compared with other reference prepared samples. FeCoNiCrMo/NF has an overpotential of 285 mV at 100 mA cm⁻² and performs continuously for 100 h without significant decline. The OER mechanism of FeCoNiCrMo/NF further reveal that Co and Ni are true active sites, and the dissolution of Cr and Mo promote the conversion of active sites into MOOH following the lattice oxygen mechanism (LOM). The precipitation–dissolution equilibrium of Fe also plays an important role in the OER process. The study of different reaction sites in complex systems points the way to designing efficient and robust catalysts. Full article

We investigated the protective properties of ultrathin laminated coatings, comprising three pairs of Al₂O₃ and TiO₂ sublayers with coating thicknesses < 150 nm, deposited on AISI 310 stainless steel (SS) and Si (100) substrates at 80–500 °C by atomic layer deposition. The coatings were chemically etched and subjected to corrosion, ultrasound, and thermal shock tests. The coating etching resistance efficiency (R_e) was determined by measuring via XRF the change in the coating sublayer mass thickness after etching in hot 80% H₂SO₄. The maximum R_e values of ≥98% for both alumina and titania sublayers were obtained for the laminates deposited at 250–400 °C on both substrates. In these coatings, the titania sublayers were crystalline. The lowest R_e values of 15% and 50% for the alumina and titania sublayers, respectively, were measured for laminate grown at 80 °C on silicon. The coatings deposited at 160–200 °C demonstrated a delay in the increase of R_e values, attributed to the changes in the titania sublayers before full crystallization. Coatings grown at higher temperatures were also more resistant to ultrasound and liquid nitrogen treatments. In contrast, coatings deposited at 125 °C on SS had better corrosion protection, as demonstrated via electrochemical impedance spectroscopy and a standard immersion test in FeCl₃ solution. Full article

Surface and sub-surface atomic configurations are critical for catalysis as they host the active sites governing electrochemical processes. This study employs density functional theory (DFT) calculations and Monte Carlo simulations combined with the cluster-expansion approach to investigate atom distribution and Pt segregation in Pt-Fe alloys across varying Pt/Fe ratios. Our simulations reveal a strong tendency for Pt atoms to segregate to the surface layer while Fe atoms enrich the sub-surface region. Crucially, the calculations predict the stability of a periodic Pt₂Fe alloy surface model, characterized by specific defect structures, at low platinum content and low annealing temperatures. Electronic structure analysis indicates that forming this Pt₂Fe surface alloy lowers the d-band center of Pt atoms, weakening CO adsorption and thereby enhancing resistance to CO poisoning. Although defect-induced strains can modulate the d-band center, crystal orbital Hamilton population (COHP) analysis confirms that such strains generally strengthen Pt-CO interactions. Therefore, the theoretical design of Pt₂Fe alloy surfaces and controlling defect density are predicted to be effective strategies for enhancing catalyst resistance to CO poisoning. This work highlights the advantages of periodic Pt₂Fe surface models for anti-CO poisoning and provides computational guidance for designing efficient Pt-based electrocatalysts. Full article

In this work, the synthesis and structural characterization of the smallest possible member of the family of bis-functionalized {MnMo₆O₂₄} Anderson–Evans polyoxometalates (POMs) is reported. The synthesis of the title compound TBA₃{[HC(CH₂O)₃]₂MnMo₆O₁₈} (1) was accomplished by using trimethylolmethane as the capping unit (TBA: tetra(n-butyl)ammonium, n-B_u4N⁺). The molecular structure of the organic–inorganic POM gave rise to yet undisclosed ¹H-NMR features, which are discussed thoroughly. Single-crystal X-ray diffraction (XRD) analysis revealed a highly regular 3D packing of the polyoxoanions within a matrix of TBA cations. The hybrid POM is of particular interest regarding potential applications in photocatalysis (i.e., hydrogen evolution) and energy storage. Thus, the electrochemical and thermal properties of 1 are also analyzed. Full article

In this study, a Ag/ZrO₂ hybrid coating prepared by the sol–gel method on a β-type Ti45Nb alloy was applied by the spin coating technique, and the microstructural, mechanical, electrochemical, and tribological properties of the surface were evaluated in a multi-dimensional manner. The hybrid solution was prepared using zirconium propoxide and silver nitrate and stabilized through a low-temperature two-stage annealing protocol. The crystal structure of the coating was determined by XRD, and the presence of dense tetragonal ZrO₂ phase and crystalline Ag phases was confirmed. SEM-EDS analyses revealed a compact coating structure of approximately 1.8 µm thickness with homogeneously distributed Ag nanoparticles on the surface. As a result of the electrochemical corrosion tests, it was determined that the open circuit potential shifted to more noble values, the corrosion current density decreased, and the corrosion rate decreased by more than 70% on the surfaces where the Ag/ZrO₂ coating was applied. In the tribological tests, a decrease in the coefficient of friction, narrowing of wear marks, and significant reduction in surface damage were observed in dry and physiological (HBSS) environments. The findings revealed that the Ag/ZrO₂ hybrid coating significantly improved the surface performance of the Ti45Nb alloy both mechanically and electrochemically and offers high potential for biomedical implant applications. Full article

In this study, a simple and effective approach was developed for the quantitative detection of serotonin. Hexagonal copper selenide nanostructures (CuSe) were employed to modify a disposable screen-printed carbon electrode (SPCE), and their ability to electrochemically detect serotonin in serum samples was investigated. The fabricated CuSe nanostructures exhibited an interconnected, cluster-like morphology composed of irregularly shaped particles with a distinct hexagonal crystal structure. The electrochemical results revealed that the CuSe/SPCE sensor showed better electrochemical activity and good analytical sensing performance towards serotonin detection. The sensor exhibited a linear response in the concentration range of 10 to 1000 nM, with an excellent correlation coefficient (R² = 0.9998) and a low detection limit of 3 nM. Furthermore, the CuSe/SPCE showed better selectivity, impressive sensitivity (12.45 µM/µA cm⁻²), and good reproducibility toward serotonin detection, making it a promising electrochemical biosensor for serotonin detection in various real biological samples. Full article

The solid electrolyte interphase (SEI) on the anode of lithium-ion batteries (LIBs) has been studied thoroughly due to its crucial importance to the battery’s long-term performance. At the same time, most studies of the SEI apply ex situ characterization methods, which may introduce artifacts or misinterpretations as they do not investigate the SEI in its unaltered state immersed in liquid battery electrolyte. Thus, in this work, we focus on using the non-destructive combination of electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) and impedance spectroscopy (EIS) in the same electrochemical cell. EQCM-D can not only probe the solidified products of the SEI but also allows for the monitoring of viscoelastic layers and viscosity changes of the electrolyte at the interphase during the SEI formation. EIS complements those results by providing electrochemical properties of the formed interphase. Our results highlight substantial differences in the physical and electrochemical properties between the SEI formed on copper and on amorphous carbon and show how formation parameters and the additive vinylene carbonate (VC) influence their growth. The EQCM-D results show consistently that much thicker SEIs are formed on carbon substrates in comparison to copper substrates. Full article

As the crucial current collector for lithium-ion batteries (LIBs), electrolytic copper foils are generally manufactured by electrodeposition in acidic copper sulfate solution. However, there are many disadvantages for traditional electrolytic copper foils, such as coarse grains, insufficient mechanical properties, and high energy consumption. In order to improve the performances of electrolytic copper foil, a novel cuprous electrodeposition system was developed in this study. A soluble cuprous coordination compound was synthesized. In addition, XPS, FT-IR spectrum, as well as single-crystal X-ray diffraction illustrated that thiourea coordinated with Cu(I) through S atom and therefore stabilized Cu(I) by the formation of CuCl·3TU. Importantly, the corresponding electrochemical behaviors were investigated. In aqueous solution, two distinct reduction processes were demonstrated by linear sweep voltammetry (LSV) at rather negative potentials, including the reduction of adsorbed state and non-adsorbed state. Moreover, the observed inductive loops in electrochemical impedance spectroscopy further confirmed the adsorption phenomenon. More significantly, the designed cuprous electrodeposition system could contribute to low energy consumptions during electrolysis. and produce ultrathin nanocrystalline copper foils with appropriate roughness. Consequently, the electrolysis method based on CuCl·3TU could provide an improved approach for copper foils manufacturing in advanced LIBs fabrication. Full article

Acrylic resin is a polymer with strong crosslinking density and strength, and it is commonly used as a matrix in water-based coatings. Barium europium phosphate (Ba₃Eu(PO₄)₃) is a novel functional filler that is expected to provide anti-corrosive effects to coatings. In this study, Ba₃Eu(PO₄)₃ was prepared by the high-temperature solid-phase method and applied to acrylic anti-corrosion coatings. The influence of the molar ratio of reactants on Ba₃Eu(PO₄)₃ purity was studied. The anti-corrosion performance of the coating was investigated. It was found that, when BaCO₃:Eu₂O₃:(NH₄)H₂PO₄ = 3:0.5:3 and the reaction was carried out at 950 °C for 1000 min, high-purity Ba₃Eu(PO₄)₃ can be obtained, according to XRD and EDS tests. SEM shows that Ba₃Eu(PO₄)₃ has good crystal morphology and a porous morphology. TEM revealed that its structure was intact. When Ba₃Eu(PO₄)₃ was added to a relative resin content of 5 wt%, the anti-corrosion performance of the coating was the best after 168 h, with the lowest Tafel current density of 9.616 μA/cm² and the largest capacitance arc curvature radius. The salt spray resistance test showed that the corrosion resistance of the 5 wt% Ba₃Eu(PO₄)₃ coating was also the best, which is consistent with the results of the electrochemical test. Ba₃Eu(PO₄)₃ as a pigment and filler can effectively improve the anti-corrosion performance of water-based industrial coatings. Full article

Nanostructured multilayer anticorrosion coatings offer an effective strategy to mitigate the poor corrosion resistance of aluminum alloys and extend their service life. In this study, four types of Ti/Cr multilayer coatings with varied modulation periods along the growth direction were deposited on 7050 aluminum alloy substrates using direct current magnetron sputtering. The cross-sectional microstructure of the coatings was characterized by scanning electron microscopy (SEM), while their mechanical and corrosion properties were systematically evaluated through nanoindentation and electrochemical measurements. The influence of modulation period distribution on the corrosion resistance of Ti/Cr multilayers was thoroughly investigated. The results show that the average thickness of the Ti/Cr multilayer coatings is 680 nm, the structure is dense, and the coarse columnar crystals are not seen. All Ti/Cr multilayer coatings significantly reduced the corrosion current density of 7050 aluminum alloy by about 10 times compared with that of the substrate, showing good protective effect. Modulation period along the coating growth direction decreases the Ti/Cr multilayer coating surface heterogeneous interface density increases, inhibits the formation of corrosion channels, hindering the penetration of corrosive media, and the other three coatings and aluminum alloy compared to its corrosion surface did not see obvious pore corrosion, showing the most excellent corrosion resistance. Full article

Green hydrogen production from water electrolysis (WE) is one of the most promising technologies to realize a decarbonized future and efficiently utilize intermittent renewable energy. Among the various WE technologies, the emerging anion exchange membrane (AEMWE) technology shows the greatest potential for producing green hydrogen at a competitive price. To achieve this goal, simple methods for the large-scale synthesis of efficient and low-cost electrocatalysts are needed. This paper proposes a very simple and scalable process for the synthesis of nanostructured NiCo- and NiFe-based electrode materials for a zero-gap AEMWE full cell. For the preparation of the cell anode, oxides with different Ni molar fractions (0.50 or 0.85) are synthesized by the sol–gel method, followed by calcination in air at different temperatures (400 or 800 °C). To fabricate the cell cathode, the oxides are reduced in a H₂/Ar atmosphere. Electrochemical testing reveals that phase purity and average crystal size significantly influence cell performance. Highly pure and finely grained electrocatalysts yield higher current densities at lower overpotentials. The best performing membrane electrode assembly exhibits a current density of 1 A cm⁻² at 2.15 V during a steady-state 150 h long stability test with 1 M KOH recirculating through the cell, the lowest series resistance at any cell potential (1.8 or 2.0 V), and the highest current density at the cut-off voltage (2.2 V) both at the beginning (1 A cm⁻²) and end of tests (1.78 A cm⁻²). The presented results pave the way to obtain, via simple and scalable techniques, cost-effective catalysts for the production of green hydrogen aimed at a wider market penetration by AEMWE. Full article

Prussian blue and its analogs (PBAs), considered potential cathode materials for sodium-ion batteries (SIBs), still confront multiple challenges. For example, many defect vacancies and high crystal water content are generated during the fast crystallization of PBAs, impairing the rate performance. The stress accumulation during Na⁺ insertion/extraction destabilizes the lattice framework and then damages the electrochemical performance. Herein, iron-based Prussian blue with an open-pore skeleton structure (PB-3) is prepared using a facile template method which employs PVP and sodium citrate to control the crystallization rate and adjust the particle morphology. The prepared materials exhibit excellent kinetic properties and are conducive to mitigate the volume changes during ion insertion/extraction processes. PB-3 electrode not only exhibits a superior rate performance (92 mAh g⁻¹ reversible capacity at 2000 mA g⁻¹), but also presents superior cycling performance (capacity retention remained at 90.2% after 600 cycles at a current density of 500 mA g⁻¹). The highly reversible sodium ion insertion/extraction mechanism of PB-3 is investigated by ex situ XRD tests, which proves that the stabilized lattice structure can enhance the long cycling performance. In addition, the considerable capacitance contributes to the rate performance. This study provides valuable insights for the subsequent development of high-performance and stable cathodes for SIBs. Full article

This study explores the development of aluminum-doped MgV₂O₄ spinel cathodes for aqueous zinc-ion batteries (AZIBs), addressing the challenges of poor Zn²⁺ ion diffusion and structural instability. Al³⁺ ions were pre-inserted into the spinel structure using a sol-gel method, which enhanced the material’s structural stability and electrical conductivity. The doping of Al³⁺ mitigates the electrostatic interactions between Zn²⁺ ions and the cathode, thereby improving ion diffusion and facilitating efficient charge/discharge processes. While pseudocapacitive behavior plays a dominant role in fast charge storage, the diffusion of Zn²⁺ within the bulk material remains crucial for long-term performance and stability. Our findings demonstrate that Al-MgV₂O₄ exhibits enhanced Zn²⁺ diffusion kinetics and robust structural integrity under high-rate cycling conditions, contributing to its high electrochemical performance. The Al-MgVO cathode retains a capacity of 254.3 mAh g⁻¹ at a high current density of 10 A g⁻¹ after 1000 cycles (93.6% retention), and 186.8 mAh g⁻¹ at 20 A g⁻¹ after 2000 cycles (90.2% retention). These improvements, driven by enhanced bulk diffusion and the stabilization of the crystal framework through Al³⁺ doping, make it a promising candidate for high-rate energy storage applications. Full article

This study investigates the development and sensing profile of synthetic melanin nanoparticle-coated electrodes for the electrochemical detection of heavy metals, including lead (Pb), cadmium (Cd), cobalt (Co), zinc (Zn), nickel (Ni), and iron (Fe). Synthetic melanin films were prepared in situ by the deacetylation of diacetoxy indole (DAI) to dihydroxy indole (DHI), followed by the deposition of DHI monomers onto indium tin oxide (ITO) and glassy carbon electrodes (GCE) using cyclic voltammetry (CV), forming a thin layer of synthetic melanin film. The deposition process was characterized by electrochemical quartz crystal microbalance (EQCM) in combination with linear sweep voltammetry (LSV) and amperometry to determine the mass and thickness of the deposited film. Surface morphology and elemental composition were examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). In contrast, Fourier-transform infrared (FTIR) and UV–Vis spectroscopy confirmed the melanin’s chemical structure and its polyphenolic functional groups. Differential pulse voltammetry (DPV) and amperometry were employed to evaluate the melanin films’ electrochemical activity and sensitivity for detecting heavy metal ions. Reproducibility and repeatability were rigorously assessed, showing consistent electrochemical performance across multiple electrodes and trials. A comparative analysis of ITO, GCE, and graphite electrodes was conducted to identify the most suitable substrate for melanin film preparation, focusing on stability, electrochemical response, and metal ion sensing efficiency. Finally, the applicability of melanin-coated electrodes was tested on in-house heavy metal water samples, exploring their potential for practical environmental monitoring of toxic heavy metals. The findings highlight synthetic melanin-coated electrodes as a promising platform for sensitive and reliable detection of iron with a sensitivity of 106 nA/ppm and a limit of quantification as low as 1 ppm. Full article

The functional performance of magnesium hydroxide (Mg(OH)₂) is intrinsically governed by its crystallographic morphology. Herein, we demonstrate an electrochemical deposition strategy to synthesize Mg(OH)₂ from abandoned MgCl₂ resources in salt lakes, achieving simultaneous waste valorization and morphology control. Systematic investigations were conducted on the effects of polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) as surfactants on electrochemical parameters (cell voltage, pH, current efficiency, and energy consumption) and morphological evolution (XRD, SEM, and laser particle size analysis). Results show that the cell voltage and pH increased proportionally with surfactant concentration, with a current efficiency of 93.86% and an optimal energy consumption of 4.15 kW h·t⁻¹ at an optimal PVP concentration of 6 g·L⁻¹. PEG addition exhibited a similar trend in process parameter modulation. Morphological evolution analysis revealed that appropriate PEG dosage promoted the transformation of irregular Mg(OH)₂ flakes into near-spherical platelets, accompanied by a measurable increase in particle size. This work establishes structure–property relationships between surfactant molecular design and Mg(OH)₂ crystallization, providing theoretical support for the controllable electrochemical preparation of magnesium hydroxide with different morphologies. Furthermore, it opens up a novel and innovative technical pathway to promote the high-value utilization of abandoned magnesium resources in salt lakes. Full article