Journal of Electroanalytical Chemistry最新文献

Metal-organic skeleton (MOF) with adjustable pore skeleton and finely reaction sites has been widely accepted in the application of high-performance supercapacitors. Here, the Se-Co-MOF-1 nano-particles obtained by modified doped Se element to Co-MOF and the CoV₃-MOF nano-sheets obtained by in-situ doped V element in Co-MOF. As a result, Se-Co-MOF-1 and CoV₃-MOF electrode materials have more electrochemical reactivity, better conductivity and better stability. At a certain current density, Se-Co-MOF-1 and CoV₃-MOF electrode materials have better mass-specific capacitance and better rate performance than Co-MOF. Furthermore, the Se-Co-MOF-1//AC ASC and CoV₃-MOF//AC ASC are also assembled, which show relatively excellent power density and energy density compared to similar work reported. The Se-Co-MOF-1//AC ASC and CoV₃-MOF//AC ASC after 10,000 cycles, their mass-specific capacitance retention rate are still 70.00 %, which further shows the reliable stability of Se-Co-MOF-1 and CoV₃-MOF electrode materials. This result proves that the synthetic schemes of MOF nano-sheets/nano-particles can be selected as the source of the strategy for preparing excellent electrode materials.

In recent years, rechargeable lithium-ion batteries (LIBs) have been extensively studied and applied in portable electronics, electric vehicles, and new energy storage devices. Gel polymer electrolytes (GPEs), currently a research hotspot, inherit the high ionic conductivity of liquid electrolytes and great mechanical properties and safety of solid electrolytes, exhibiting great application potential. Herein, we demonstrate a flexible flame retardant GPE (PPC37) that forms a polymer network through intermolecular hydrogen bonding. During the charge–discharge cycle, the formation of a LiF-rich solid electrolyte interface (SEI) facilitates the uniform electrochemical deposition of Li⁺ and achieves a long life cycle without dendrites. PPC37 possesses high ionic conductivity (1.06 mS cm⁻¹ at 25 °C) and robust mechanical properties (198% fracture length and 2.43 MPa fracture strength). The Li|PPC37|LiFePO₄ batteries presented great cycling stability with an initial capacity of 151.9 mAh/g and a discharge capacity retention of 86.4% after 500 cycles at a high current density of 3C at 55 °C. The excellent thermal stability, interfacial stability, flame retardancy, flexibility and electrochemical stability demonstrated with PPC37 demonstrate the safety of high-temperature batteries, indicating their great application potential in flexible electronic devices and high-temperature environments.

In this study, ZnO/NiO@NC was prepared using polyvinylpyrrolidone (PVP) as a structural guide and carbon source, and an oxygen-vacancy-rich ZnO/NiO@N-doped carbon shell (ZnO/NiO@NC) electrode material was obtained by annealing under an N₂ atmosphere. When the current density of the galvanostatic charge–discharge (GCD) was set to 0.5 A/g, the ZnO/NiO@NC electrode exhibited maximum specific capacitance (860.00 F/g), longer charge/discharge time, and a lower impedance compared with other materials. Its specific capacity was maintained above 80%, indicating that the active material had superior stability owing to encapsulation by the carbon shell. The excellent electrochemical performance is attributed to the formation of an effective p-n heterostructure between ZnO and NiO as the basic skeleton, surface oxygen vacancies, and the rich mesoporous structure after high-temperature reduction calcination. Furthermore, the excellent electrical conductivity of the N-doped carbon shell further improves the electrochemical performance of the material.

Suppressing the lithium polysulfides (LiPSs) shuttle and facilitating ion and charge transport in the electrode component resulting in effective sulfur conversion, is essential for the efficient functioning of lithium-sulfur (Li-S) batteries have substantial sulfur loading. In this study, a multifunctional cathode material based on a three-dimensional MXene and g-C₃N₄ hollow spheres framework was designed. This design aimed to create a conductive Platform with high absorptive and catalytic capability that would boost the performance of Li-S batteries in practical operating conditions. At the electrode level, the 3D hollow spherical architecture offers a large surface area to achieve high sulfur loading, preserves structure integrity in the electrode over significant volume changes of sulfur species, and facilitates diffusion of Li⁺ and electrolyte flow. At the molecular level, the pyridinic structure of g-C₃N₄ and the MXene conductive platform allows for fast sulfur conversion. The cathode, consisting sulfur ratio of 80%, exhibits a remarkable primary specific capacity of 1350.6 mAhg⁻¹ at 0.1C. It retains 877.2 mAhg⁻¹ after 100 cycles, showing a 65.2% retention rate. Furthermore, it exhibits exceptional electrochemical properties in terms of rate performance, giving a capacity of 632.5 mAhg⁻¹ at a current of 4C. Our findings may have future technological consequences since they may speed the development of cost-effective and more efficient electrode materials for Li-S batteries.

The ligands [R-Fc(cyclen)], [Fc(cyclen)₂], [Fc(cyclam)₂], [Fc₂(cyclen)] and [Fc₄(cyclen)] (R = –H or –CH₂OH; Fc = ferrocene; cyclen = 1,4,7,10-tetraazacyclododecane; cyclam = 1,4,8,11-tetraazacyclotetradecane) and their respective Cu²⁺, Co²⁺, Cd²⁺, Zn²⁺, and Ni²⁺ metal complexes have been synthesised and electrochemically characterised. The voltammetry of the free ligands in a CH₂Cl₂/CH₃CN (1:4) solvent mixture containing [Bu₄N][PF₆] or [Bu₄N](B(C₆F₅)₄] as the supporting electrolyte yields two closely spaced oxidation processes. The first one is Fc based, and the other is related to the interaction of the Fc with the nitrogen component. Details of the mechanism were established by studying the oxidation of N,N-dimethylaminomethylferrocene by cyclic voltammetry and bulk electrolysis with product isolation. However, cyclic voltammetries exhibit a single Fc-based reversible oxidation process when the ligands form metal complexes with Cu²⁺, Co²⁺, Cd²⁺, Zn²⁺, or Ni²⁺. Upon metal ion binding, an important positive shift in the reversible midpoint potential, E_m, is observed. The magnitude of the shift in the E_m values follows the order [Fc(cyclen)₂] ≈ [Fc(cyclam)₂] ≫ [R-Fc(cyclen)] ≈ [Fc₂(cyclen)] > [Fc₄(cyclen)]. The ability of the ligands to work as electrochemical sensors for the mentioned cations is discussed.

Achieving cobalt superconformal (bottom-up) growth is significantly important. Electrochemical methods, including cyclic voltammetry, electrochemical impedance spectra and EQCM-derived Coulomb-voltage curves, were used to confirm the suppressing influence of new suppressor Nitrotetrazolium Blue chloride (NBT). In situ Raman spectroscopy was used confirm that NBT can effectively adsorb on cobalt surface. Besides, EQCM-derived Coulomb-voltage illustrates that it is more beneficial for cobalt electrodeposition at high pH. The NBT effect on hydrogen evolution reaction (HER) was studied by LSV and chronoamperometry. Finite element simulation is used to investigate the accelerating effect of NBT on HER and convection. Suppressing-accelerating effect is proposed to illustrate effect of NBT. NBT can not only suppress the cobalt deposition but also can accelerate local convection by intensifying HER, which can in turn strengthen NBT adsorption. SEM analysis demonstrates that convection and NBT can refine grain. High-quality cobalt is achieved with low SDT values ranging from 24 μm to 45 μm and high FP values (75.4 % for 150 μm, 88.9 % for 100 μm and 87.2 % for 50 μm).

The purpose of this work is to systematically investigate the effect of F⁻ on the electrochemical properties and electrodeposition nucleation of Ce(III) in LiCl-KCl molten salt. Electrochemically reversible, three-electron transfer and diffusion-controlled Ce(III)/Ce redox reactions were still observed by using Cyclic voltammetry (CV), Square wave voltammetry (SWV), and Chronopotentiometry (CP) methods in the LiCl-KCl molten salt containing F⁻. With the addition of F⁻, a negative shift in peak and equilibrium potentials were observed, indicating that F⁻ could interact with Ce(III) via the coordination competition with Cl⁻. Also, F⁻ ions were found to decrease both the diffusion coefficient and exchange current density j₀ of Ce(III). In addition, the thermodynamic data of Ce(III)/Ce at multiple F⁻ concentrations were calculated theoretically, which showed that Ce(III) preferred to form [CeCl₅F]³⁻complexes in chlorine molten salts. Finally, the effect of F⁻ on the electrodeposition nucleation mechanism of Ce(III) at tungsten electrodes was studied. The results showed that the nucleation and growth mechanism shifted from instantaneous nucleation to between instantaneous and progressive nucleation with the addition of F⁻. The current research paves a new way for changing the nucleation mode of electrodeposition, which provides a new direction to retrieve the uranium dendrites during the electrorefining of spent nuclear fuel.

N-rich multilayered carbon nanofibers with hollow channels (PPMPN) are fabricated to fully utilize the mesopores, micropores, and nitrogen-functional groups of carbon nanofibers (CNFs) for superior electrochemical properties. Among all composites, the PPMPN(10) exhibits high specific surface area (570 m²g⁻¹) with mesopore volume fraction (42%) and rich surface functionalities (∼7.25at% nitrogen and ∼ 16.1at% oxygen), helping to improve electrochemical performance. The performance of the symmetric supercapacitor of the PPMPN was significantly improved in terms of its specific capacitance of 189 Fg⁻¹ at 1 mAcm⁻², good retention of 80% (when the current density is increased from 1 to 20 mAcm⁻²), energy density of 23.5 Whkg⁻¹ at a power density of 400 Wkg⁻¹, and cycling stability of 94% for 10,000 cycles. The top layer plays a role in charge storage/transport by increasing electrical conductivity due to N-functional groups. The intermediate layer with tubular 1D nanostructures enhances the diffusion of electrolyte ions even at higher current densities. The bottom layer composed of numerous micropores serves as a charge storage layer. Therefore, in the multilayer CNF, the micropores/mesopores and N-functional properties of each layer do not interfere with each other, and the advantages of the factors of each layer are maximized in the electrochemical properties.

CuInS₂ thin films have been successfully synthesized from the electrodeposition of copper (Cu), indium (In), and sulfurization on a molybdenum glass substrate as a water splitting photocathode. The effect of various sources of sulfurization with thiourea, sulphur, and H₂S and modification with Pt-In₂S₃ on the character and performance of the material was observed. The success of the synthesis was confirmed by the typical peaks of 28.2, 46.8, and 55.4° on XRD, the presence of Cu, In, S elements on SEM-EDX analysis, the appearance of peaks of 298 cm⁻¹ on Raman analysis, and the detection peaks of Cu 2p, In 3d, and S 2p with XPS analysis. Meanwhile, performance effectiveness and photoelectrochemical properties were analysed with photocurrent linear sweep voltammetry (LSV), applied bias photon-to-current efficiency (ABPE), and incident photon-to-current conversion efficiency (IPCE). Variations of sulfurization sources give different character and photocurrent results due to differences in the existing reaction mechanisms. While the modification treatment with Pt-In₂S₃ increased the resulting photocurrent. Sulfurization with H₂S and modification of Pt-In₂S₃ gave the best results with a photocurrent of 18 mA cm⁻², an efficiency of 3% ABPE, 47.2% IPCE, was evolved 467 μmol H₂ and 230,1 μmol O₂. This shows good potential as a water splitting material to produce environmentally friendly hydrogen fuel.

Development of an effective electrocatalyst for the electrochemical water splitting to store electrical energy as H₂ fuel and improve sluggish oxygen evolution reaction (OER) is the need of the time. For H₂ production and making it more accessible, developing a low-cost fabrication method for an efficient OER catalyst with characteristics including a large surface area, an abundance of active sites, and exceptional stability is necessary. In this study, neodymium-doped manganese oxide (Nd-MnO) with a larger specific surface area (32.6 m²/g), small size particles (84 nm), and most crucially high concentration of oxygen vacancies fabricated via a simple solution reduction method using NaBH₄ as a reductant. Nd-MnO has an overpotential of 394 mV and a Tafel slope value of 84 mV/dec reaching 10 mA/cm², superior to RuO₂ and MnO. The potential results of the Nd-MnO are due to a unique structure consisting of nanocubes that may enhance OH ion mass diffusion/transport and offer a large number of active sites for catalysis of OER, as well as oxygen vacancies which are also validated by DFT that may enhance the electronic conductivity and provide H₂O adsorption on the surface of neighboring Mn³⁺ sites.