Journal of Electroanalytical Chemistry最新文献

In this paper, an amperometric biosensor model with substrate and product inhibition kinetics is analysed. This model is a steady-state system of reaction-diffusion equations with non-linear terms related to non-Michaelis-Menten kinetics of an enzymatic reaction. We present the approximate analytical expression of the substrate and product concentrations using well-founded methods, namely the Taylors series method (TSM) and the Adomian decomposition method (ADM). These methods proved that they fit for all values of parameters in this model. The steady-state biosensor current, biosensor substrate sensitivity and resistance are also discussed. We also present the numerical solution of the described model using MATLAB programming, and it is noted that there is satisfactory agreement in comparing the analytical solution with numerical results for all possible values of parameters. The effects of the parameters, such as inhibition constants, diffusion parameters, bulk concentration and Michaelis-Menten constant on the sensitivity and the resistance of the biosensor are analysed.

Electrochemical reduction of nitrate to NH₃ is a very promising alternative reaction to the Haber-Bosch process, and it is necessary to develop the efficient electrocatalysts. In this study, a particle-support mode Co₃O₄ catalyst was synthesized with ZIF-67 as the precursor, and then dispersed on MoS₂ nanoflowers by hydrothermal method. The Co₃O₄ is anchored to MoS₂ by forming Co-S coordination bond. Furthermore, the particle-supported Co₃O₄ exhibits better performance than Co₃O₄ alone, as is manifested by higher Faradaic efficiencies and NH₃ yield rate at − 0.64 V (52.69% vs 32.03%; 4539.61 μg h⁻¹ mg⁻¹_cat vs 2048.63 μg h⁻¹ mg⁻¹_cat), lower energy barriers (0.96 eV vs 1.19 eV), and better electronic conductivity (Bandwidth: 0.581 eV vs 0.613 eV). In addition, this research provides an effective solution to solve the aggregation problem of metal oxide nanoparticles.

Among many alternatives to fossil fuel-based energy systems, one of the most promising is based on hydrogen energy and its production and use in unitized regenerative fuel cells as the primary energy conversion devices. However, there are some setbacks and challenges when designing suitable and efficient electrocatalysts for these devices. The most effective and durable catalysts are based on platinum–group metals, with low abundance and unbearably high prices. Many attempts were undertaken to overcome this setback by designing catalysts suitable for massive commercial use. This review paper focuses on recent advances in developing bifunctional catalysts for oxygen reduction and oxygen evolution catalysis in alkaline media, based on abundant transition metal oxides (TMOs): MnO₂, NiO, and TiO₂. The problem of unifying parameters to compare the effectiveness of different electrocatalysts is emphasized. This review discusses the most promising alternative bifunctional electrocatalysts by comparing the performance of TMOs with some precious metal catalysts used as benchmarks.

Safety issues of common rechargeable Li-ion batteries (LIB) necessitate urgent development of alternative high-performance electrode materials. Lithiated nickel-rich oxides (LiNi_1-x-yMn_xCo_yO₂) are promising LIB cathode materials, but they suffer from structural instabilities causing major capacity loss. To address this issue, here we use a robust ethanol-based wet coating process to coat a LiNi_0.8Co_0.1Mn_0.1O₂ LIB cathode material with polyanionic compound TiP₂O_7. The coating layer does not affect the phase structure of LiNi_0.8Co_0.1Mn_0.1O₂ and ensures a remarkable electrochemical performance, evidenced by the high initial Coulombic efficiency, durable cyclic stability, and excellent rate performance. The mechanisms leading to the achieved improvements are related to the effects of the coating layer which improved the Li⁺ diffusion capability and the electrochemical polarization. The TiP₂O₇ layer protects the electrode from the electrolyte by suppressing side reactions such as HF acidic attack and the associated dissolution of transition metal ion. Moreover, the unique three-dimensional (XO_n)^m- framework of the TiP₂O₇ polyanion provides plentiful accommodation sites and channels for the Li-ions diffusion. The demonstrated approach opens new avenues for practical applications of electrochemically active coatings in diverse energy storage devices and systems.

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.

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.

Carbon layer-encompassed nickel nanoparticles of core–shell structure (designated as Ni NPs@NC) show notable advantages toward electrochemical carbon dioxide reduction reaction (CO₂RR). Core-shell structured Ni NPs@NC nanoparticles anchored on the carbon matrix have been conveniently built from a cationic metal–organic framework (CPM-72 herein) which incorporates the Ni²⁺ cations through the cation exchange before high-temperature pyrolysis. The designed Ni NPs@NC catalyst exhibited impressive CO₂RR performance which could efficiently convert CO₂ into CO (carbon monoxide). In the H-type cell, a maximal CO faradaic efficiency (FE) of 86.4% was achieved at −0.8 V (vs. RHE) with a high CO partial current density (j_co) of −11.0 mA cm⁻². In the flow cell device, the CO FE was further improved to 98.6% with the enhanced j_co of −38.7 mA cm⁻². Finally, Zn-CO₂ battery test also delivered a peak power density of 0.39 mW cm⁻² at 2.65 mA cm⁻².

Nanosized-silver substrates with smooth surface and fine particles were fabricated by a non-cyanide pulse electrochemical deposition. The electrochemical behavior of silver electrochemical deposition was investigated with a series of electrochemical methods. Cyclic Voltammetry and chronopotentiometry showed that the overpotential was significantly reduced when silver ions were continuously deposited on the silver layer. During deposition, the nucleation mechanism gradually changed from the progressive nucleation to the instantaneous nucleation with the negative shift of potential. The effect of pulse period θ on the Surface Enhanced Raman Scattering performance of the substrate was investigated. Combined with Scanning Electron Microscope, X-ray diffraction, 2D SERS Mapping and Raman spectrum, the pulse period θ was optimized. The enhancement effect of the substrates was relatively uniform, and the enhancement factor for rhodamine 6G was 5.34 × 10⁶, the detection limit could be as low as 1.0 × 10⁻¹³ mol·L⁻¹. The optimized substrate obtained good linear range and low detection limit in the detection of contraband pigment sunset yellow, indicating that the substrate may have a good application prospect in the actual detection.

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.

In the wake of environmental enigmas including global warming and the exhaustion of traditional hydrocarbon sediments, the usage of eco-friendly power generation is of paramount importance today. Alternatives to traditional fossil fuels such as hydrogen are clean, safe, and environmentally friendly. Moreover, hydrogen as a renewable energy source, as the only by product of burning hydrogen is water. Many electrochemical energy conversion methods rely on the oxygen evolution reaction (OER), but creating effectual, economical electrocatalysts for it has proven difficult. The multifunctional electrocatalyst, nickel selenide-anchored cobalt telluride, has been found to be effective in catalyzing oxygen evolution processes in alkaline medium. CoTe and NiSe, generated hydrothermally, exhibit promising electrocatalytic activity. However, their composite NiSe@CoTe, possesses higher OER durability. The presence of NiSe in the CoTe matrix responses a powerful OER responses due to the synergistic effect in alkaline environment. The NiSe@CoTe nanocomposite shows minimal Tafel value (39 mV/dec) and lower overpotential (247 mV) to attain a current density of 10 mA/cm², whereas the pristine CoTe and NiSe needed higher overpotential to attain same current density. Following 16 h of utilizing the same catalyst, OER stability was maintained with 88 % current density retention.