Journal of Electroanalytical Chemistry最新文献

This work presents a comprehensive degradation study of two types of large lithium-ion pouch cells; 26 NMC532/Graphite (64 Ah) and 9 NMC433/Graphite (31 Ah) pouch cells. The cells were degraded under different cycling conditions and periodically characterized at room temperature. Specifically, the effect of different ambient temperatures and constraining the cells by clamping was studied. Incremental capacity analysis is an in situ, non-invasive characterization technique that allows the identification of battery degradation modes, and is a technique that does not require additional and advanced equipment. Therefore, in this study we also look into applying the analysis technique on an existing data set. This is done by combining incremental capacity analysis on a qualitative level with the tracking of features of interest in the incremental capacity curve as a function of State of Health and utilizing the simulation of different degradation modes for a more in-depth analysis. We combine simulation and experimental incremental capacity analysis with conclusions from capacity loss and resistance changes with a focus on understanding the benefit and limitations of the incremental capacity analysis for large cells. This is important, as incremental capacity analysis is a relatively fast analysis to qualify large commercial batteries for 2nd life applications. Specifically in this study, we found that degradation and capacity loss do not always correlate. For the 64 Ah Cells cycled at 15 °C and 25 °C, the rate of capacity loss appeared to be similar, although the degradation modes and mechanisms are found to be very different. The clamping was the most important factor for impeding degradation. The 31 Ah Cell cycled at low temperatures showed a very poor cycling performance, where the incremental capacity analysis revealed that Loss of Lithium Inventory from fast and irreversible plating was responsible.

A molecularly imprinted, polypyrrole based, sensor with significant enantioselective recognition ability for D- and L- glutamic acids was prepared using a multi-current steps technique on framed silver screened printed electrodes (Ag-SPE). The surfaces of the silver nanoparticles were passivated to obtain a dense, thick MIP film, which was able to inhibit the dissolution of Ag-SPE during the potentiostatic monomer electropolymerization at high positive applied potentials. After template removal, a pretreatment step was carried out at 10 V (vs. Ag/AgCl) to induce template binding and bring about the oxidative dissolution of printed silver particles on the SPE. From the i-t curves, application of the break-down current was found to be needed for only a shorter time for the template-free solution, while no such breakdown was found for the test solution containing the template molecule, implying that the MIP film provided a high resistance that inhibited Ag-SPE dissolution. After pretreatment for 600 s, the optimum selectivities for D- and l-glutamine on their template imprinted films were L/D = (145.9 ± 17.3)/1 and D/L = (126.0 ± 15.4)/1 respectively, based on the current change between 0 and 2 V (vs. Ag/AgCl) with the two enantiomers being present at the same concentration (10 mM). The imprinted glutamic acid films were characterized using scanning electron microscopy with energy dispersive spectroscopy. A recognition mechanism, related to the dissolution of Ag-SPE in the pretreatment step at positive potentials is also proposed.

The search for alternative electrolytes is extremely topical in recent years with the “water-in-salt” electrolyte especially, lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) coming to the fore in the context of high-voltage electrolytes. However, “water-in-LiTFSI” exhibits ultra-high cost and low ionic transport when compared with the aqueous lithium- halide, -nitrate as well as -sulphate salts. This work rediscovered the properties of a “water-in-salt” made from a superconcentrated 20 m (equivalent to 14.28 M) lithium chloride electrolyte. The electrolyte was tested using various carbon-based materials as a model system, and the finding was then expanded to a pouch cell supercapacitor. It is found that the use of superconcentrated LiCl could enhance the potential window of the supercapacitor in both half-cell electrodes (approximately of 3.0 V), and pouch-cell devices (1.4 V evaluated at 100 mV s⁻¹). This work shows the fundamental insight into the physical and electrochemical properties of LiCl for possible alternative use as a cheap “water-in-salt” electrolyte in energy storage apart from LiTFSI.

CuF₂ is a promising candidate of electrode materials for lithium-ion batteries due to its high specific capacity, high power density and environmental friendliness. However, the irreversible phase conversion and sluggish kinetics caused by serious copper dissolution and low conductivity make CuF₂ difficult to achieve long cycling life. A facile strategy to incorporate CoPPc into CuF₂ was proposed firstly to regulate the Cu-F bonding force to realize the high reversibility of CuF₂ for lithium-ion storage. The results of DFT calculation, differential charge density simulation, work function calculation and COHP bond level calculation show that the existence of CoPPc can improve the surface charge distribution of CuF₂ and thus improve the reversibility for durable lithium-ion storage. The cycle life performance of the CuF₂@CoPPc composite electrode obtained by this method reached staggering 500 cycles and the capacity remained at 594.8 mAh/g.

Covalent organic frameworks (COFs), a newly emerging kind of porous material, have gained extensive attention due to their fascinating structural features. However, the superiority of COFs as electrochemical sensing materials has not yet been adequately explored. Herein, a new type of core–shell metal–organic framework (MOF)@COF composites are synthesized through in situ growth of TAPB-DMTP-COF on the pre-synthesized Ce-BDC core. The thickness of the COF shell can be controlled to 20–50 nm by adjusting the Ce-MOF mass. It is found that the obtained MOF@COF composite possesses a larger electrochemical active area and faster electron transfer kinetic than its single component. As a case application of this composite, it has been employed as a sensing material for voltammetric detection of metol, where a linear range from 0.1 − 200 μM and a detection limit of 30 nM have been obtained. This study provides a new strategy to synthesize COF-based electrode materials as well as to explore their electrochemical properties and applications.

Fe₂O₃ has been considered as a promising anode material for lithium-ion batteries (LIBs) owing to its high specific capacity. However, its sluggish charge transfer resulting from the poor electrical conductivity severely limits the electrochemical performance. In this work, an ultrathin Fe₃O₄ layer-coated Fe₂O₃ composite was fabricated through a facile one-step hydrothermal method with hydrazine hydrate as the reductant in an alkaline environment. Upon use as the anode for LIBS, the as-resulted Fe₂O₃@Fe₃O₄ composite achieves a high specific capacity of 1539.5 mA h g⁻¹ at a current density of 100 mA g⁻¹ and simultaneously maintains a high discharge capacity of 707.8 mAh g⁻¹ after 800 cycles at 1000 mA g⁻¹, outperforming the commercial Fe₂O₃ sample. Electrochemical characterizations reveal that the improved electrochemical performance can be attributed to the combined effects of higher theoretical specific capacity of Fe₂O₃ and superior electrical conductivity of Fe₃O₄.

The possibility of producing high-purity and ligand-free nanoparticles makes laser ablation in liquids (LAL) an interesting method to produce gold nanoparticles (AuNPs). AuNPs play an important role in the manufacture of electrochemical sensors due to their excellent electrical conductivity and chemical stability. In this study, stable and ligand-free AuNPs were produced by LAL (AuNP/LAL) using a nanosecond pulsed laser. The control of this single-step production was facilitated by adding sodium chloride (NaCl), resulting in the reduction of AuNPs size (10 ± 2 nm) and higher stability (monitored for 12 weeks). The potential of NaCl-stabilized AuNPs/LAL as modifiers agents were investigated for dopamine (DA) sensing by cyclic voltammetry for the first time. The novel electrochemical sensor (GCE/AuNPs.LAL/Nafion) achieved an increase in the peak current of ca. 3 and 6 times for oxidation and reduction, respectively. A comparison of chemical syntheses and LAL approaches was given for electrochemical sensing applications; the AuNPs/LAL showed to be more efficient in facilitating the electronic transfer and electrocatalytic reactions. The estimated limit of detection values for DA sensing was 0.77 µmol/L (oxidation) and 1.08 µmol/L (reduction). The method hereby proposed is promising for clinical applications as the new electrochemical sensor allowed proper sensitivity for DA.

As the main energy supply of human social activities, fossil fuels have caused serious pollution to the global environment, so it is extremely urgent to find new green renewable energy. Hydrogen has entered people's field of vision because of its high energy density, no carbon emission, easy storage, transportation, etc. However, the current industrial hydrogen production can still be realized by using fossil fuels, which cannot effectively solve the global pollution problem. Hydrogen production by electrocatalytic water splitting is green and has no by-products, but its development is inhibited by thermodynamic and kinetic obstacles. Therefore, developing a reasonable electrocatalyst to reduce the reaction energy barrier is a difficult problem that must be overcome. Noble metals Ir, Ru, and their oxides have good performance when used as electrocatalysts, but they cannot be used on a large scale due to the cost and content of materials. Transition metals and their oxides, especially spinel materials, also have good performance as electrocatalysts. As a typical inverse spinel, NiFe₂O₄ is considered a promising OER electrocatalyst because of its high storage, low price, high stability, corrosion resistance, and environmental friendliness. In this paper, the achievements of NiFe₂O₄ used as electrocatalysts in recent years are reviewed. The evaluation parameters and reaction mechanism of OER were introduced firstly, then the physical and chemical properties, electronic structure, and synthesis methods of NiFe₂O₄ were introduced, and various modification strategies for improving the OER efficiency of NiFe₂O₄ in recent years were classified and analyzed emphatically, and the most effective strategies for modifying NiFe₂O₄ were found out. Then the development prospect of NiFe₂O₄ electrocatalyst has prospected.

The abundant and renewable nature of lignin obtained from wood renders it as a sustainable carbon resource for energy storage applications. However, their environmentally unfavorable processing conditions and limited energy storage performance prohibit the use of lignin-based carbon materials' use as supercapacitor electrodes. The material's properties require advancement to overcome the limitation of low specific capacitances. In this study, we report on the impact on the electrochemical performance of inherently hydrophobic lignin-based carbon fibers (LCF) by subjecting them to a mild plasma treatment. The electrode’s capacitance was thus increased by 20%, with better rate capability and energy-power performance (11 Wh/kg and 0.8 kW/kg) in the KOH electrolyte. The quantified improvements were attributed to the capacitive functional groups, and enhanced surface wettability, which increased ion accessibility to active surface area improving charge-transfer ability to the surface with more additional functional groups. Remarkably, the selected plasma conditions introduced mostly desirable functional groups that limited any parasitic faradaic reactions prone to affect the device's long-term cycling stability and self-discharge characteristics. Furthermore, the impact of different inherent and introduced oxygen surface functional groups, including COO⁻, COH, CO, and CO, on the capacitive performance of these fibers at different device conditions (such as cycling and electrochemical activation) was investigated in different aqueous electrolytes. To ensure environmental favorability, the electrospinning of lignin fibers was conducted using a high molecular fraction of lignin without the inclusion of any fossil-based co-spinning polymers.

Small size Au nanoparticles (AuNPs) have aroused wide interest in electrochemical sensing due to its high surface atom utilization and superior electrical conductivity. However, there was a great challenge to balance the stability and small-size of AuNPs because of their large specific surface and high surface energy. Regarding this issue, herein, COF_TAPB-DMTP was proposed as guiding support substrate for the synthesis of highly dispersed and small size AuNPs, where the uniform functional sites such N, O atoms on COF_TAPB-DMTP could act as anchor points to induce in-situ reduction of AuNPs, and the confinement effects from the nanopore of COF_TAPB-DMTP could limit their size. Then, an electrochemical paracetamol (PA) sensor was designed based on AuNPs@COF_TAPB-DMTP since the abundant active centers and outstanding electrical conductivity of highly dispersed small size AuNPs conferred the composite excellent sensing performance. Moreover, the large specific surface, ordered pore channels and abundant heteroatomic functional groups of COF_TAPB-DMTP could achieve high enrichment capacity toward PA molecules on electrode surface through pore effect, hydrogen bonding and electrostatic interaction. Benefiting from the combination between AuNPs and COF_TAPB-DMTP, the AuNPs@COF_TAPB-DMTP based sensor presents excellent analytical performance in term of low limit of detection (22 nM), satisfactory stability, reproducibility and selectivity. It indicated that COFs can be used as promising inducible substrate material for the preparation of highly dispersed and small size metal nanoparticles.