Journal of Electroanalytical Chemistry最新文献

As the key step in the overall water splitting system, hydrogen evolution reaction (HER) has become one of the main methods of hydrogen production in industrial applications. Here, through the strong coupling between NiCo-LDH nanosheets and NiCoS nanorods, the three-dimensional heterogeneous structure formed by the composite can provide a large catalytic specific surface area. The modification of LDH lamellar will provide abundant edge active sites and enhance its structural stability. The synergistic effect of NiCo-LDH and NiCoS can optimize the electronic structure and promote mass transfer and water cracking. Benefiting from the above points, the NiCoS@NiCo-LDH/NF obtained showed the significant boost in HER process. It only required 99 mV to reach current density of 10 mA·cm⁻² and maintained excellent durability for 24 h for HER, which proved NiCoS@NiCo-LDH/NF was a cost-free, high-efficient and outstandingly stable HER catalyst in basic solution.

This study investigates glass/Ti/Pt/TiO₂ surfaces, wherein Pt nanoparticles (NPs) were potentiostatically deposited with an amount of Pt that varies based on deposition time. The size and distribution of NPs were analyzed by scanning electron microscopy (SEM). Subsequently, a thicker titanium dioxide film was grown via anodization. Topography and roughness were examined by atomic force microscopy (AFM). Remarkably, TiO₂ grows independently of Pt NPs and remains stable under working conditions, including acid, neutral, and alkaline media. Under steady-state conditions, the open circuit potentials (OCPs) of the modified semiconductor/electrolyte interfaces corresponding to 1, 5, and 10 s of electrodeposited Pt, showed a shift of 167 mV, 42 mV, and 24 mV toward more positive values, respectively. Notably, these surfaces exhibit the activity of a Pt quasi-electrode and the band structure of a titanium dioxide semiconductor, making them ideal for use as photoanodes. In addition, it can be highlighted that the methodology employed in the preparation of the surfaces allows for reproducibility.

The development of non noble metal electrocatalysts with high OER catalytic activity has become an urgent demand for water cracking. In this work, NiFe LDH nanobulks grown on CNTs were prepared by a green and simple one pot hydrothermal method. The acidified CNTs usually include hydroxyl, carboxyl and other oxygen-containing functional groups, which make the carbon tubes have a certain negative charge. The negatively charged CNTs can interact with the positively charged NiFe LDH nanobulks in an electrostatic manner, resulting in a self-assembly reaction to slow down the agglomeration of NiFe LDH nanobulks, better highlight the advantages of two-dimensional material structure, and expose greater specific surface area of activity. The introduction of CNTs can enhance the conductivity of the composite, accelerate the charge transfer in the reaction process, and further improve the OER catalytic performance of NiFe LDH/CNTs catalyst materials.

Antioxidant can protect body from free radical and dietary intake is a major source of antioxidants for human body. Therefore, it is particularly important to evaluate the antioxidant capacity of food and drink in daily diet. Herein, a label-free photoelectrochemical (PEC) sensor based on BiVO₄@graphene oxide (GO) hybrid has been developed for antioxidants analysis and applied it to antioxidant capacity detection of real samples. Five representative antioxidants including ascorbic acid (AA), caffeic acid (CA), chlorogenic acid (CHA), fisetin (FT) and quercetin (QT) were determined by this PEC sensor to acquire photocurrent response at different concentrations. This PEC sensor exhibited excellent sensitivity and anti-interference. Furthermore, antioxidant capacity of food samples was assessed utilizing this PEC sensor, indicating the practicability and accuracy of this PEC sensor. This study suggests that BiVO₄@GO composites constructed PEC sensor can provide a practical and fast method for detecting antioxidant capacity in the field of food.

CuO quantum dots (QDs)-embedded Cu₃(BTC)₂/CuO sugar gourd-like nanoarrays are successfully assembled on copper foil through a two-step wet-chemical growth method. As a free-standing anode for lithium-ion batteries, the resultant composite (Cu-BTC/QDs/CuO@Cu) delivers a high specific capacity of 813 mAh/g at a current density of 0.2 A/g after 150 cycles, and 452 mAh/g at 1.0 A/g after 500 cycles, demonstrating excellent cycling stability and rate performance. The superior energy storage capability is attributed to a synergistic effect from the individual components including the electro-active organic ligand, porous framework and CuO nanowires/QDs. As an efficient binder-free anode, Cu-BTC/QDs/CuO@Cu can be a promising candidate for the development of high-performance and cost-effective LIBs with exceptional energy density and power density capabilities.

The overall conversion efficiency of water electrolysis is primarily restricted by the sluggish kinetics of the oxygen evolution reaction (OER). To overcome the OER bottleneck, fundamental scientific attention is keenly directed toward the development of durable, cost-effective, and highly efficient catalysts, and therefore, the focus of current research. Herein, we report the facile fabrication of promising noble–metal–free oxygen defects engineered MnCo₂O₄ (O_d-MnCo₂O₄) catalyst as a highly efficient OER water electrocatalyst in an alkaline KOH medium. The MnCo₂O₄ nanosheet is directly grown on the nickel foam and dramatically changes to a crumpled sphere after NaBH₄ treatment, which results in increased oxygen defects (O_d). The engineered O_d in MnCo₂O₄ might modify their electronic structure effectively, which results in improved electrical conductivity and a large quantity of electrochemically accessible active surface area. The O_d-MnCo₂O₄ catalyst demonstrates an outstanding OER activity and exhibits a small overpotential of 250 and 316 mV at a current density of 10 and 100 mA cm⁻², respectively, with a modest Tafel slope of 64 mV dec^–1. The O_d-MnCo₂O₄ catalyst also demonstrates excellent perseverance till 60 h upon continuous chronopotentiometric test even at 100 mA cm⁻² and further reveals a static potential response at low and high rates. The excellent OER performance is ascribed to enhanced electrochemically active sites and improved electronic conductivity aroused from the NaBH₄ reduction.

The class of quinone compounds are excellent representatives of biologically redox-active compounds. Electron transfers such as in quinone compounds play important roles in the bioactivation of redox-active drugs, in their metabolism/catabolism, and targeted release at precise destinations and frequently promote their ligand–target interactions. Owing to the enthralling synthetic importance and pharmacological applications of 1,4-naphthoquinone derivatives, our interest is turned into a detailed electro- and photoelectrochemistry study of these pharmacophoric structures. Firstly, amino(substituted)-1,4-naphthoquinone (NQ) derivatives (2a-b, 3, 4a-b, 5, 6, 7, 8 and 9) were synthesized according to Michael addition mechanism. The exact structures of compounds were elucidated by spectroscopic methods such as FT-IR, ¹H-/¹³C NMR, MS and microanalysis. Secondly, the electrochemical behaviors of NQ derivatives are determined with voltammetric and in situ UV–Vis spectroelectrochemical measurements. All synthesized NQ derivatives illustrate two reductions and one oxidation processes. Voltammetric analyses of the couples of the molecules indicate electrochemical reversibility of the reductions and electrochemical irreversibility of the oxidation couples. Substituent environments of NQ structure considerably influence the chemical reversibility of the redox processes.

Commercial separators result in poor lithium battery performance due to low electrolyte wettability and non-selective ion transport. In this work, the cellulose membrane with excellent electrolyte wettability was selected as the skeleton, and the MOF nanoparticles were added by the blending method. The composite cellulose membrane with uniform pore size was prepared by casting process. The cellulose membrane skeleton promoted the absorption of electrolytes. The Lewis acid sites presented in UiO-66 facilitated the dissociation of lithium salts by attracting PF₆⁻ anions. The OMS (open metal site) provided by UiO-66(Ce) further adsorbs anions and solvent molecules, effectively regulated ion transport, maintained a stable and efficient cycle life, and reduced lithium dendrite deposition. The LiFePO₄/Li equipped with UiO-66/CM showed a capacity retention rate of 71.70%, while the LiFePO₄/Li equipped with UiO-66 (Ce)/CM showed a capacity retention rate of 93.80 % after 200 cycles at 0.5C. Therefore, the developed strategy may provide a powerful way to improve electrolyte wettability and effectively regulate ion transport.

Urea oxidation reaction (UOR) is considered as a good substitute for oxygen evolution reaction (OER) because of its low theoretical onset potential. Surface modification is an effective strategy to tune the catalytic activity of the catalysts towards UOR. Here, we developed a facile and universal quenching strategy to prepare sulfate-modified NiO nanosheets (NiO@NF-20S). Compared with the pristine NiO nanosheets, the electrocatalytic performance of the NiO@NF-20S is greatly improved, showing a small potential of 1.40 V vs. RHE to deliver a current density of 200 mA cm⁻² as well as robust electrochemical stability. The outstanding electrocatalytic performance of the NiO@NF-20S is mainly ascribed to the improved surface wettability and the promoted Ni²⁺/Ni³⁺ redox reaction. The quenching strategy can be expanded to not only various kinds of functional groups from nitric acid and phosphoric acid but also other metal oxides such as NiCoO_x and NiCrO_x. This work provides a new avenue to the design of surface-functionalized metal oxide catalysts for electrocatalysis.

A classical electrochemistry problem related to the polarization of a graphene electrode immersed in an aqueous solution and subjected to a small external ac voltage is revisited. The Poisson-Nernst-Planck equations with proper boundary conditions are linearized and normalized, leading to an analytical formula for the impedance of the electrochemical system containing a graphene-metal electrode pair. Electrochemical impedance spectroscopy is utilized to compare the impedance behavior of the graphene-metal electrode pair with the standard metal-metal electrode pair for a range of ion concentrations in the electrolyte. Also studied is the electrochemical capacitive spectroscopy to provide a detailed analysis related to the effects of the quantum capacitance of graphene on the total capacitive properties of the system.