Electrochemical Properties Research Articles

Doping Engineering of Sodium Vanadium Fluorophosphates Cathodes for Sodium-Ion Batteries

Abstract Sodium-ion batteries offer a promising alternative to lithium-ion batteries due to the abundance and low cost of sodium resources. Na3V2(PO4)2F3−y O y (NVPFO y ) stands out as a cathode material with high average operating potential (~ 3.9 V vs Na+/Na), fast Na⁺ transport, and strong structural stability (minimal volumetric strain of ~ 2%). This review addresses the structural characteristics and charge storage mechanisms of NVPFO y , focusing on charge compensation and Na⁺/vacancy ordering. It also discusses recent advances in lattice regulation and doping strategies to enhance electrochemical properties. Finally, we highlight challenges and future directions for practical applications, emphasizing the correlation between crystal structure and performance.

Synthesis of Graphene Nanosheets from Coconut and Candlenut Shells: Large-Scale Production and Application in Fe Ion Adsorption and Electrochemical Properties

Synthesis of Graphene Nanosheets from Coconut and Candlenut Shells: Large-Scale Production and Application in Fe Ion Adsorption and Electrochemical Properties

Effect of growth dynamics on the structural, photophysical and pseudocapacitance properties of famatinite copper antimony sulphide colloidal nanostructures (including nanosheets).

Facile phase selective synthesis of copper antimony sulphide (CAS) nanostructures is important because of their tunable photoconductive and electrochemical properties. In this study, off-stoichiometric famatinite phase CAS (fCAS) quasi-spherical and quasi-hexagonal colloidal nanostructures (including nanosheets) of sizes, 2.4-18.0 nm were grown under variable conditions of temperature (60-200 °C), time and oleylamine capping ligand concentration using copper(II) acetylacetonate and antimony(III) diethyldithiocarbamate precursors. Data from powder X-ray diffraction, Raman spectroscopy and high-resolution scanning/transmission electron microscopy confirm the tetragonal structure of the famatinite phase. X-ray photoelectron spectroscopy, transmission electron microscopy and scanning electron microscopy-energy dispersive X-ray spectroscopy data suggest a correlation of particle size, morphology and composition of the off-stoichiometric fCAS nanostructures with growth temperature and time, and oleylamine concentration. The off-stoichiometric Cu3-aSb1+bS4±c (a, b, c - mole fractions) nanostructures being severely copper-deficient and antimony-rich, exhibit shallow-lying acceptor copper vacancy states, deep-lying donor states of antimony interstitials, sulphur vacancies and antimony-copper antisites and shallow-lying acceptor surface trapping states. These electronic states are likely implicated in tunable UV-visible absorption and bandgaps between 2.3 and 2.8 eV, and broad visible-NIR photoluminescence with fast recombination of radiative lifetimes between 0.2 and 6.2 ns, confirmed from absorption, steady-state and time-resolved photoluminescence spectroscopies. Additionally, cyclic voltammetry and electrochemical impedance spectroscopy confirm that electrodes of the fCAS nanostructures display slightly variable pseudocapacitance of charge-storage primarily via possible sodium ion intercalation with a high specific capacitance of ∼84 F g-1 obtained at a scan rate of 5 mV s-1. Overall, these results show the influence of composition, in particular point defects, phase quality and morphology on the optical and pseudocapacitance properties of fCAS nanostructures, suitable as solar absorbers or electrodes for energy storage devices.

Breaking Anionic Solvation Barrier for Safe and Durable Potassium-ion Batteries Under Ultrahigh-Voltage Operation.

Ultrahigh-voltage potassium-ion batteries (PIBs) with cost competitiveness represent a viable route towards high energy battery systems. Nevertheless, rapid capacity decay with poor Coulombic efficiencies remains intractable, mainly attributed to interfacial instability from aggressive potassium metal anodes and cathodes. Additionally, high reactivity of K metal and flammable electrolytes pose severe safety hazards. Herein, a weakly solvating fluorinated electrolyte with intrinsically nonflammable feature is successfully developed to enable an ultrahigh-voltage (up to 5.5 V) operation. Through breaking the anionic solvation barrier, synergistic interfacial modulation can be achieved by the formation of robust anion-derived inorganic-rich electrode-electrolyte interfaces on both the cathode and anode. As proof of concept, a representative KVPO4F cathode can sustain 1600 cycles with 84.4% of capacity retention at a high cutoff voltage of 4.95 V. Meanwhile, K plating/stripping process in our designed electrolyte also demonstrates optimized electrochemical reversibility and stability with effectively inhibited potassium dendrites. These findings underscore the critical impact of anion-dominated solvation configuration on synergistic interfacial modulation and electrochemical properties. This work provides new insights into rational design of ultrahigh-voltage and safe electrolyte for advanced PIBs.

A comparative study on the structural, chemical, morphological and electrochemical properties of α-MnO2, β-MnO2 and δ-MnO2 as cathode materials in aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are considered to be highly promising electrochemical energy storage device due to their affordability, inherent safety, large zinc resources, and optimal specific capacity. Among various cathode materials, manganese dioxide (MnO2) stands out for its high voltage, environmental benignity, and theoretical specific capacity. This study systematically investigates the phase formation and structural parameters of α-MnO2, β-MnO2, and δ-MnO2 synthesized via hydrothermal method, employing Rietveld refinement. FTIR and Raman spectroscopy confirms Mn-O and O-H bond formation. BET analysis reveals surface areas, and pore size distribution is calculated with BJH method. High-resolution XPS spectra exhibit a spin energy split of ~ 11.9 eV for Mn 2p confirming the presence of MnO2. Electrochemical studies shows an initial discharge capacities of 230.5, 188.74 and 263.30 mAh g− 1 at 0.1 A g− 1 for α-MnO2, β-MnO2 and δ-MnO2. The EIS spectra revealed the capacitive behaviour and electrode reaction kinetics where a RcT value of 484.14, 327.6, 162.5 Ω for α-MnO2, β-MnO2 and δ-MnO2. These study give insights into relation of various properties of MnO2 with electrochemical performance and its viability in grid storage applications.Graphical

Structure and Morphological Properties of Cobalt-Oxide-Based (Co3O4) Materials as Electrodes for Supercapacitors: A Brief Review

Over the past 15 years, there has been a significant increase in the search for environmentally friendly energy sources, and transition-metal-based energy storage devices are leading the way in these new technologies. Supercapacitors are attractive in this regard due to their superior energy storage capabilities. Electrode materials, which are crucial components of supercapacitors, such as cobalt-oxide-based electrodes, have great qualities for achieving high supercapacitor performance. This brief review presents some basic concepts and recent findings on cobalt-based materials used to fabricate electrodes for supercapacitors. The text also clarifies how morphological characteristics typically influence certain properties. The inner surface of the electrode exhibits several properties that change to provide it a great boost in specific capacitance and charge storage. Porous structures with defined pore sizes and shapes and high surface areas are important features for improving electrochemical properties. Finally, we present some perspectives for the development of cobalt-oxide-based supercapacitors, focusing on their structure and properties.

Electrochemical Properties of ZrNi1.2 Mn0.5Cr0.2V0.1 and ZrNi1.2 Mn0.45Cr0.2V0.15 Alloy Electrodes Depending on Discharge Modes

Electrochemical Properties of ZrNi1.2 Mn0.5Cr0.2V0.1 and ZrNi1.2 Mn0.45Cr0.2V0.15 Alloy Electrodes Depending on Discharge Modes

Electrochemical and physical properties of magnesioferrite nanomaterial and photocatalytic degradation of methylene blue

This research successfully synthesized semiconductive magnesioferrite (MgFe2O4) nanomaterials using a green chemistry method that utilizes the natural extract of Moringa olefeira serving as both a reducing and oxidizing agent. The optical characteristics and crystalline structure of the MgFe2O4 nanomaterials were analysed using photoluminescence, diffuse reflectance spectroscopy, and X-ray diffraction. Additionally, Fourier transform infrared spectroscopy provided valuable insights into the chemical bonding and composition. High-resolution transmission electron microscopy was employed to obtain extensive information on crystalline size and distribution. Furthermore, the electrochemical properties were assessed through cyclic voltammetry and electrochemical impedance spectroscopy, revealing an excellent voltametric response and pseudo-capacitive behaviour associated with faradaic reactions, as well as outstanding conductivity linked to the unique charge transport mechanisms present in the MgFe2O4 structure. The effectiveness of the MgFe2O4 nanomaterials in the photodegradation of methylene blue from aqueous solutions was evaluated under visible light irradiation. Photocatalytic experiments measured the influence of various parameters, including catalyst loading, dye concentration, and pH. The MgFe2O4 nanomaterials exhibited impressive photocatalytic degradation efficiency, achieving an 81% degradation rate at pH 5.0 within 120 min. Kinetic studies indicated that the degradation process adhered to a pseudo-first-order model, with a rate constant of 0.01533 min−1, signifying a rapid reaction under optimal conditions. This study provides a thorough understanding of the electrochemical properties and enhanced photocatalytic capabilities of MgFe2O4 nanomaterials, thereby advancing green nanotechnology for environmental remediation.

Simulating Ionized States in Realistic Chemical Environments with Algebraic Diagrammatic Construction Theory and Polarizable Embedding.

Theoretical simulations of electron detachment processes are vital for understanding chemical redox reactions, semiconductor and electrochemical properties, and high-energy radiation damage. However, accurate calculations of ionized electronic states are very challenging due to their open-shell nature, importance of electron correlation effects, and strong interactions with chemical environment. In this work, we present an efficient approach based on algebraic diagrammatic construction theory with polarizable embedding that allows to accurately simulate ionized electronic states in condensed-phase or biochemical environments (PE-IP-ADC). We showcase the capabilities of PE-IP-ADC by computing the vertical ionization energy (VIE) of thymine molecule solvated in bulk water. Our results show that the second- and third-order PE-IP-ADC methods combined with the basis of set of triple-ζ quality yield a solvent-induced shift in VIE of -0.92 and -0.93 eV, respectively, in an excellent agreement with experimental estimate of -0.9 eV. This work demonstrates the power of PE-IP-ADC approach for simulating charged electronic states in realistic chemical environments and motivates its further development.

Molecular Determinants of Optical Modulation in ssDNA-Carbon Nanotube Biosensors.

Most traditional optical biosensors operate through molecular recognition, where ligand binding causes conformational changes that lead to optical perturbations in the emitting motif. Optical sensors developed from single-stranded DNA-functionalized single-walled carbon nanotubes (ssDNA-SWCNTs) have started to make useful contributions to biological research. However, the mechanisms underlying their function have remained poorly understood. In this study, we combine experimental and computational approaches to show that ligand binding alone is not sufficient for optical modulation in this class of synthetic biosensors. Instead, the optical response that occurs after ligand binding is highly dependent on the chemical properties of the ligands, resembling mechanisms seen in activity-based biosensors. Specifically, we show that in ssDNA-SWCNT catecholamine sensors, the optical response correlates positively with the electron density on the aryl motif, even among ligands with similar ligand binding affinities. Importantly, despite the strong correlations with electrochemical properties, we find that catechol oxidation itself is not necessary to drive the sensor optical response. We discuss how these findings could serve as a framework for tuning the performance of existing sensors and guiding the development of new biosensors of this class.

Fabrication of MoS2@Fe3O4 Magnetic Catalysts with Photo-Fenton Reaction for Enhancing Tetracycline Degradation

Tetracycline (TCs) is widely used in the treatment of human and animal infectious disease. TCs gives rise to a growing threat to the human health and environment protection due to its overuse. Therefore, it is important to remove TCs contaminants from waste effluents. In this work, MoS2@Fe3O4 catalytic material was fabricated by the simple hydrothermal method, which was applied in the photo-Fenton system to degrade TCs. The crystal structure, surface morphology, elemental composition, chemical state, electrochemical properties, and separability of MoS2@Fe3O4 catalytic materials were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), conventional and high-resolution transmission electron microscopy (TEM/HRTEM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and vibrating sample magnetometry (VSM). Furthermore, MoS2@Fe3O4 could degrade 98.6% of TCs within 60 min under the optimum reaction conditions (the catalyst dosage of 3 g/L, H2O2 concentration of 5 mmol/L, the initial TCs concentration of 50 mg/L, and the initial pH of 5), which was a significant increase compared with pure Fe3O4. MoS2 can accelerate the Fe3+/Fe2+ cycle through electron transfer from Mo4+ to Fe3+, resulting in the improvement in the degradation efficiency of TCs. The quenching and electron paramagnetic resonance (EPR) results showed that OH• and photogenic hole h+ was the main active species in the photo-Fenton system. What is more, MoS2@Fe3O4 catalytic materials had remarkable stability and reusability, and can be handily regained via magnetic separation technology in a real scenario.

Low-Impedance Hybrid Carbon Structures on SiOX: A Sequential Gas-Phase Coating Approach.

Carbon coating on SiOX surface is crucial for enhancing initial Coulombic efficiency (ICE) and cycling performance in batteries, while also buffering volume expansion. Despite its market prevalence, the effects of the carbon layer's quality and structure on the electrochemical properties of SiOX remain underexplored. This study compares carbon layers produced via gas-phase and solid-phase coating methods, introducing an innovative technique that sequentially uses two gases to develop a low-impedance hybrid carbon structure. In this approach, C3H8 is first deposited to create a short-range, vertically ordered carbon architecture, followed by C2H2 to establish a long-range, layered structure, effectively filling the gaps. This results in a dense hybrid carbon layer characterized by minimal defects, high crystallinity, and excellent electronic conductivity. The dominant vertical configuration enhances Li-ion migration. The SiO@C3H8@C2H2 prepared through this method yields a specific surface area of 1.14 m2 g⁻¹ and a high reversible capacity of 1574.9 mAh g⁻¹, alongside an ICE of 83.7%. It showcases remarkable cycling stability, retaining 86.6% capacity after 1000 cycles at room temperature, and performs effectively under varied temperatures and discharging conditions. This low-impedance carbon structure provides a significant reference for other anodes that also require a carbon layer.

Conducting Polymer Microelectrode Arrays for Simultaneous Electrophysiology and Advanced Brain Imaging

AbstractIn neuroscience research and clinical practice, electrophysiology is used to record and stimulate specific parts of the brain with high temporal resolution. This capability can be augmented by magnetic resonance imaging (MRI), which provides anatomical and functional information about the brain with large spatial coverage. However, metallic electrodes, commonly used in electrophysiology, are fundamentally incompatible with MRI due to heating concerns and imaging artefacts. Here, it is demonstrated that flexible micro‐electrocorticography (µECoG) arrays, with electrodes made of poly(3,4‐ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS), are compatible with ultra‐high magnetic field MRI up to 9.4 T. A scalable fabrication process is adopted that results in very repeatable electrochemical properties across devices. The volumetric capacitance of PEDOT:PSS leads to low electrode impedance and enables high‐resolution neural recordings of single‐unit activity from the cortical surface of rodents. Furthermore, the µECoG array creates minimal distortion in T2‐weighted anatomical brain MRI. Multimodal brain monitoring is demonstrated by performing simultaneous blood oxygen level‐dependent functional MRI (BOLD fMRI) in parallel with electrical stimulation from the µECoG array. The results show that the PEDOT:PSS µECoG arrays enable the combination of high‐resolution electrophysiology and advanced brain imaging in vivo.

Synthesis of Nonplanar Push-Pull Chromophores with Various Heterocyclic Moieties via [2 + 2] Cycloaddition-Retroelectrocyclization Reaction.

A series of 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) derivatives with various heterocyclic moieties, including pyridine, carbazole, indole, and benzothiadiazole, was newly synthesized through a [2 + 2] cycloaddition-retroelectrocyclization reaction. Symmetric electron-rich 1,3-butadiynes with end-capped heterocyclic substituents were reacted with tetracyanoethylene (TCNE), yielding the target TCBD products in 60-80% yields under ambient or mild heating conditions. The thermal stability and optical and electrochemical properties of both 1,3-butadiyne precursors and the corresponding TCBD derivatives were investigated by using thermogravimetric analysis (TGA), UV-vis spectroscopy, and cyclic voltammetry (CV). The TCBD derivatives featured narrow bandgaps due to the intramolecular charge transfer interactions of push-pull chromophores. In addition, the optimized structures and frontier molecular orbitals with their energy levels were determined by density functional theory (DFT) calculations.

Engineered ionic polymer metal composites (eIPMCs) under dynamic compression loading conditions: Theory and experiments

Abstract Engineered Ionic Polymer Metal Composites (eIPMCs) represent the next generation of IPMCs, soft electro-chemo-mechanically coupled smart materials used as actuators and sensors. Recent studies indicate that eIPMC sensors, featuring unique microstructures at the interface between the ionic polymer membrane and the electrode, exhibit enhanced electrochemical behavior and sensitivity under compression, as compared to traditional IPMCs. However, a complete and experimentally-validated model of how eIPMCs behave under dynamic compression loads is currently missing. In this paper, we develop an analytical model for eIPMC sensors, elucidating the role of the engineered interface, modeled as a separate material layer with unique mechanical and electrochemical properties. Theoretical predictions focus on the mechanical-to-electrochemical transduction response under dynamic compressive loads. Experimental verification is conducted on conventional IPMC and novel eIPMC samples fabricated using the polymer abrading technique. Electrochemical impedance spectroscopy is performed to study the effect of the engineered interface on the electrochemical properties. Open-circuit voltage and short-circuit current are measured under external compressive loads in different loading scenarios to demonstrate sensing performance. Results show good qualitative agreement between experimental trends and model predictions. Experiments over the frequency range 1-18 Hz demonstrate an increase of 220-290% in open-circuit voltage and 17-166% in short-circuit current sensitivity for eIPMCs over IPMCs.

Growth of Oxide and Nitride Layers on Titanium Foil and Their Electrochemical Properties

The surface of titanium foil can be modified by heating in the air, in a N2 flow, and in an NH3 flow. Upon heating in the air, the elemental Ti gradually transforms to Ti3O at 550 °C and to rutile TiO2 at above 700 °C. Treatment in a N2 flow leads similarly to Ti3O at 600 °C and TiO2 at 700 °C, although the overall reaction is slower. Meanwhile, nitridation in the N2 flow is minimal, even at 900 °C. Heat treatment in an NH3 flow produces nitride phases through the ammonolysis of the hexagonal Ti. With an ammonolysis at 900 °C, trigonal Ti2N and cubic TiN form together while, at higher temperatures, TiN is dominant. The TiN layer can also be obtained via the ammonolysis of the TiO2 coating, that is, by the sequential treatments of Ti in the air and then in an NH3 flow. The titanium nitride layers have particulate microstructures and varying degrees of porosity, depending on the ammonolysis temperature and time. The TiO2-derived TiN has a significantly higher capacitance than TiN derived directly from Ti. The optimally prepared TiN specimen exhibits an areal specific capacitance of 66.2 F/cm2 at 0.034 mA/cm2.

N-Doped Zigzag-Type Aromatic Truncated Cone Belts.

Zigzag aromatic hydrocarbon belts, ultrashort segments of zigzag carbon nanotubes, have been fascinating in the chemistry community for more than a half century because of their aesthetically appealing molecular nanostructures and tantalizing applications. Precise introduction of heteroatoms of distinct electronegativity and electronic configuration can create various heterocyclic aromatic nanobelts with novel physical and chemical properties. Here, we report the synthesis of unprecedented N-doped zigzag-type aromatic belts, belt[n]pyrrole[n]pyridines (n = 6-8), from multiple intramolecular Caryl-Caryl homocoupling reactions of readily available azacalix[n](3,5-dibromopyridine)s. These compounds adopt globally π-conjugated belt structures and display unique photophysical and electrochemical properties. The truncated cone cavity of belt[8]pyrrole[8]pyridine was used as the outstanding host to form very stable 2:1 encapsulation complexes with fullerenes. This work opens a new avenue to the rational design and efficient synthesis of aromatic belts of distinct topological structures and tailor-made properties, which are invaluable in applications in materials and supramolecular chemistry.

Three dimensional CNTs interweaved layered MnTe nanoparticles as a new cathode for aqueous zinc ion battery.

Currently, the development of suitable transition metal chalcogenides (TMDs) for aqueous zinc ion batteries (AZIBs) is plagued by the terrible conductivity and electrochemical properties. Herein, a one-step ball milling method is applied to enhance the conductivity of commercial MnTe cathode by constructing three dimensional (3D) carbon nanotubes (CNTs) interweaved MnTe nanoparticles (abbreviated as MnTe@CNTs), which can achieve ultrafast ion conduction. The stable electrochemistry properties benefit from the synergistic effects between layered MnTe and 3D CNTs, which can improve the electrons/ions diffusion kinetics as cycling. So MnTe@CNTs achieves a ultra-high capacity of 427.2 mAh g-1 at 0.1 A g-1 and superior capacity retention of 97.6% at 1 A g-1 over 200 cycles. Zinc-storage mechanisms can be revealed with the aid of operando XRD and ex situ XPS spectra. MnTe as a new cathode presents superior Zn-storage ability for high-performance AZIBs.

Multiple Reaction Pathways for Oxygen Evolution as a Key Factor for the Catalytic Activity of Nickel-Iron (Oxy)Hydroxides.

We present a comprehensive theoretical study, using state-of-the-art density functional theory simulations, of the structural and electrochemical properties of amorphous pristine and iron-doped nickel-(oxy)hydroxide catalyst films for water oxidation in alkaline solutions, referred to as NiCat and Fe:NiCat. Our simulations accurately capture the structural changes in locally ordered units, as reported by X-ray absorption spectroscopy, when the catalyst films are activated by exposure to a positive potential. We emphasize the critical role of proton-coupled electron transfer in the reversible oxidation of Ni(II) to Ni(III/IV) during this activation. After establishing the structural models of NiCat and Fe:NiCat consistent with experimental data, we used them to explore the atomistic mechanism of the oxygen evolution reaction (OER), which is triggered once the applied potential exceeds the overpotential required for water oxidation and oxygen production. We quantitatively compared seven OER pathways applicable to both the adsorbate evolution mechanism (AEM) and the lattice-oxygen-mediated mechanism (LOM) families, elucidating how iron significantly enhances the catalytic activity of Fe:NiCat compared to NiCat. Our findings suggest that simple metal-oxygen-metal motifs, common on the surface of both crystalline and amorphous metal (oxy)hydroxide films, can promote both AEM and LOM mechanisms under typical OER conditions. Furthermore, we propose that the elusive role of iron lies in the distinct behavior of Ni(IV)-O and Fe(IV)-O bonds in key intermediates preceding the formation of the O-O bond, with Fe ions lowering the potential needed to form these intermediates across the investigated pathways.

Synthesis and electrochemical properties of V-doped SnO2 anode materials

Synthesis and electrochemical properties of V-doped SnO2 anode materials