Journal of Electroanalytical Chemistry最新文献

The nanocrystalline Ni-Sn coatings (average grain size 15.78 nm) formed of relatively ordered circular particles covering the entire surface characterized with nodule-like endings were successfully electrodeposited using pulse electrodeposition technique. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD) were used to analyse the film microstructure. The corrosion resistance and semiconducting properties of Ni-Sn coatings were investigated in borate buffer solution. The EIS measurements showed that Ni-Sn alloys developed, in the passive zone, a good corrosion resistance as demonstrated by a thin film thickness, the low capacitance value, high polarization resistance, and the high value of electric field strength. Mott-Schottky analysis showed that the passive film formed on Ni-Sn coatings presents an p-n heterojunction characteristic indicating that the charge carrier densities are composed of cation (N_A) and anion (N_D) vacancies. The high density of point defects (N_A + N_D ∼ 10²¹cm⁻³) induces a high electronic conductivity in the Ni-Sn coatings passive film. The XPS analysis showed that the passive film formed on Ni-Sn alloys is composed of NiO, Ni(OH)₂, NiOOH, SnO, and SnO₂ species and an enrichment of Sn in the passive film. The mechanisms of passive film growth and Sn segregation in the Ni-Sn passive film are suggested in conjunction with the Point Defect Model (PDM). The good corrosion resistance and high electronic conductivity achieved in this work suggest that Ni-Sn Coating is a good candidate for water electrolysis applications.

Extended use of Triclosan (TCS), in many pharmaceutical, medical devices, personal care products and home cleaning products constitutes a potential concern to the human health and ecological system due to its vast exposure into ground water, sediments and surface water. Its prolonged environmental presence and recognized persistence have sparked scientific and societal concern, which has promoted research into efficient remediation methods. In order to resolve this concern, we have designed a ternary nanocomposite of rGO modified porous Cu-benzene tricarboxylic acid metal organic framework (Cu-BTC MOF) decorated NiCo bimetallic nanoparticle by adopting a solvothermal route. High electrical conductivity of rGO, greater surface area of Cu-BTC MOF, and the electrocatalytic nature of NiCo bimetallic nanoparticles collectively enhance the electrochemical property of the designed sensor. Cyclic voltammetry and impedance measurement showcased our fabricated nanocomposite possessed highest conductivity and supported our aim to achieve a potential sensor for electrochemical sensing of TCS. Under optimum conditions, from the square wave voltammetry (SWV) analysis our sensor was found to have detection limit 0.23 × 10⁻¹² M (0.67 × 10⁻⁷µg/ml) and a wide linear detection range of 49 × 10⁻⁶ M to 0.39 × 10⁻¹² M with sensitivity of 0.196 µA/mM. The proposed sensor further displayed desired selectivity, outstanding stability, and good repeatability, demonstrating its successful detection capabilities for harmful TCS.

This paper presents a study on the effect of the precursor structure on NMC811 electrochemical properties. The influence of different parameters, such as morphology and crystallinity of the precursor, Ni_0.8Mn_0.1Co_0.1(OH)₂, on the final electrochemical performance of NMC811 are analyzed. To ensure a correct and fast mixing of the precursor reactants and prepare the Ni_0.8Co_0.1Mn_0.1(OH)₂, a novel approach is used employing a micromixer, thus enabling the collection of the precipitated metal hydroxide within a few seconds after its precipitation. Then the precursor is calcinated together with a Li source to obtain the NMC811 cathode material. When analyzing the aging time of the precursor, between collection and calcination, it is observed that the primary particles of the precursor grow and become more crystalline, adopting a lamellar shape, while the secondary particles turn more compact, when increasing the aging time. The NMC materials synthesized from the aged precursors have smoother primary particles, exposing clearer crystalline planes. This change in morphology is also evidenced in the crystalline structure where an increase in the aging time produces better layered materials with a lower cation mixing index. The well-ordered structure impacts the electrochemical characteristics; indeed, the aged precursor produces NMC with higher specific capacity, better cyclability and lower capacity fade.

An increasing number of electrochemical biosensors have been constructed to detect single bioactive substances with high sensitivity, but not multiple bioactive substances with different properties. Therefore, we incorporated Cu and Fe elements into Prussian blue to form Prussian blue analogues (PBA) to improve the electrochemical catalytic activity of Prussian blue. At the same time, MoS₂ is used as the material substrate to increase the electrochemical active site of the composite. We have constructed a universal electrochemical sensing platform using composite materials (CuFe PBA/MoS₂) as electrode modification materials for detecting two different types of representative cancer biomarkers, hydrogen peroxide (H₂O₂) and carcinoembryonic antigen (CEA). The universal electrochemical biosensor showed a significant linear response to both H₂O₂ and CEA with the lowest detection limits of 0.23 μM and 0.01 ng mL⁻¹, respectively, and it had high selectivity, reproducibility, and stability. The universal electrochemical biosensor is successfully applied to detect H₂O₂ released from human breast cancer (MCF-7) cells and CEA expressed on the surface of human cervical cancer (HeLa) cells. The developed biosensor has potential in the dynamic detection of the flux of H₂O₂ and the expression level of CEA from living cells. The high sensitivity of this universal sensor provides a novel strategy for simultaneously detecting multiple cancer biomarkers.

In this study, CoSe₂/NC composites with stable dodecahedral structures were prepared by a simple one-step carbonization-selenization method using ZIF-67 as the precursor, and the effect of annealing time on their morphology and properties was investigated. SEM and TEM characterization results showed that the material with an annealing time of 1 h had the most stable framework structure and complete selenization. Under a three-electrode system with 2.0 M KOH as the electrolyte, CoSe₂/NC-1 possesses a high capacity of 554.4F/g at 1 A/g and excellent cycling stability (92% capacity retention after 21,000 cycles). In addition, a flexible solid-state supercapacitor was assembled with CoSe₂/NC-1 as the positive electrode and AC as the negative electrode. The power density was 800 W/Kg at 1 A/g, and the cycling stability was tested at 91.53% after 6000 cycles at 2 A/g. The flexible solid-state supercapacitors were tested for suppleness, and their voltage could still reach 1.6 V with stable specific capacity and light up LED bulbs when measured at 0°, 90° and 180°. Undoubtedly, the CoSe₂/NC-1 material prepared in this study exhibits promising electrochemical characteristics, making it a viable candidate for implementation in flexible solid-state supercapacitors.

Nanostructured transition metal sulfides (TMSs) have attracted great attention owing to their superior electric conductivity and easy redox reaction properties in oxygen evolution reaction (OER) catalysts. However, the strong metal-metalloid bonds (M−S) and metalloid-metalloid (SS) bonds in the crystal structure of TMSs are difficult to break, which might result in the insufficient formation of electrocatalytically active metal hydroxide species on the surface and prevent the realization of their full OER potential. Herein, we demonstrate an approach by sculpting Co(OH)₂ on Co₃S₄ nanotubes (Co₃S₄/Co(OH)₂) as highly reactive and stable electrocatalysts for efficient OER. The electron transfer between cobalt and sulfur and the pre-sculpted Co(OH)₂ promote the formation of rich hydroxide active species on the surface of Co₃S₄/Co(OH)₂. The optimized Co₃S₄/Co(OH)₂–0.8 catalyst possesses excellent electrocatalytic activity for OER in an alkaline medium, with a relatively low OER overpotential of 269 mV (at 10 mA cm⁻²) and a Tafel slope of 95.2 mV dec^-1. This work provides a new sight of designing TMS electrocatalysts for practical application in efficient water splitting.

LiMn₂O₄ cathode materials have been regarded as one of the promising candidates for aqueous zinc-ion batteries. However, their actual application is still hindered by the Mn²⁺ dissolution and structural transformation during the charge/discharge cycling. Herein, we synthesized LiMn₂O₄ cathode materials with octahedron morphologies and followed introducing oxygen vacancies by the calcination treatment in Ar. Octahedral shape is beneficial to the improvement of cycle stability of LiMn₂O₄ cathode materials. Oxygen vacancies contribute to the rate performance by improving the electronic conductivity. Nevertheless, the cycling stability of LiMn₂O₄ cathode materials with oxygen vacancies is not satisfactory. So, we proposed the synergistic strategy of TiO₂-coating LiMn₂O₄ and oxygen vacancies. TiO₂@(LMO-A0.5) sample with uniform thin TiO₂ coating was obtained by regulating the hydrolysis reaction of tetrabutyl titanate. Consequently, TiO₂@(LMO-A0.5) exhibits the impressive rate capability and cycling stability (as high as 85 mAh/g and 91.22% capacity retentions after 200 cycles at 0.1 A g⁻¹) as the cathode materials for aqueous zinc-ion batteries. The synergetic development of multiple strategies may endow LiMn₂O₄ cathode materials with magical perspectives in aqueous zinc-ion batteries.

As histamine is one of the important mediators for allergic reactions, its efficient detection methods and real-time monitoring systems are required for food analyses and drug discoveries to suppress allergic reactions. Although histamine dehydrogenase (HmDH) is a promising candidate for developing enzyme-based electrochemical biosensors, some electron mediators are frequently employed to observe electrocatalytic currents for histamine oxidation. Here, direct electrochemistry of HmDH was studied at the surface of graphite nanofibers (GNFs), which provide active reaction sites for redox species. Air plasma-treated GNFs were used for constructing a three-dimensional network that works both as an electrical nanowire and an enzyme support. Even though the amount of oxygen-containing functional groups didn’t significantly increase at the GNF surface with increase in the air plasma treatment time, direct electron transfer from reduced HmDH by histamine to the GNFs was improved probably due to capped and curvature of the graphite edge sites with oxygen-containing functional groups, which were generated by the air plasma treatment. The air plasma-treated GNFs also allowed enhancement of the complex-formation reaction rate of HmDH with histamine, as the air plasma treatment time increased.

This work compares the electrode reaction mechanisms of 100 cm² class molten carbonate cells (MCCs) operated in electrolysis cell (EC) and fuel cell (FC) modes using a reactant gas addition (RA) method. The RA method reveals essential information on an electrode reaction mechanism by measuring the overpotential of an electrode resulting from adding a reactant. The hydrogen electrode (HE) is revealed to be under a gas-phase mass transfer-controlled process in both modes. In addition, the HE overpotential at an inlet composition of H₂: CO₂: H₂O = 0.3: 0.3: 0.4 atm is caused mainly by H₂ species in FC mode, while CO₂ contributes the majority in EC mode due to the production of H₂ and consumption of CO₂ by the water–gas shift reaction. On the other hand, most of the oxygen electrode (OE) overpotential is contributed by O₂ species in both modes. The overpotential induced by O₂ species was larger in FC mode than EC mode because EC mode generates O₂ and provides less mass transfer resistance of O₂ species in the liquid phase. The addition of CO₂ to the OE raised overpotential in both modes. The overpotential was especially large in FC mode due to the reduced O₂ partial pressure and relatively low in EC mode because of O₂ generation. Therefore, the total overpotential in EC mode is less than in FC mode.

A facile route was proposed in preparing phosphorus and nitrogen dual carbon quantum dots (N,P-CQD) from banana flower bract extract by hydrothermal synthesis for selective and reliable detection of catecholamines such as dopamine (DA). By morphologically characterizing the synthesized CQD using Transmission Electron Microscopy (TEM), it is discovered that its average particle size is 3.8 nm. While the doping of the heteroatoms upsurges the electrical conductivity of the CQD, the presence of the functional sites like acid (–COOH), (–NH₂) and phosphate (-PO₄^3-) groups selectively attract the cations via., an ion-exchange mechanism leaving behind the anions, due to the electrostatic repulsion. The synthesized N,P-CQD/PIGE electrode-based electrochemical sensors demonstrated high selectivity and sensitivity for DA with a relatively low limit of detection (LOD) (∼500 pM) and a wide linear range, extending from 6.0 μM to 0.1 mM. The N,P-CQD's detection selectivity is further validated by utilizing a combination with a somewhat larger concentration of uric (UA) and ascorbic (AA) acids and only a modest amount of DA. Additionally, the N,P-CQD/PIGE electrode successfully detects DA with a LOD as low as 630 pM and a larger linear range of 2.5 M to 0.16 mM in real-time samples of dopamine injection.