Journal of Electroanalytical Chemistry最新文献

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.

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.

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.

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 carbon dioxide reduction reaction (CO₂RR) is a key reaction that efficiently uses CO₂ to produce value-added chemicals. However, the main limitation of this reaction is its low selectivity which results in the formation of a variety of by-products. As a result, the current challenge for CO₂RR is the efficient formation of product with high Faradaic efficiency (FE). Our main goal is to replace precious metal electrocatalysts with more abundant transition metal/conducting support hybrid catalysts. Herein, we’ve synthesized a cuprite-polyaniline (Cu₂O@PANI) composites. The superior catalytic activity in terms of activity and selectivity for methanol (MeOH) synthesis could be attributed to the synergism between Cu₂O and PANI that enables it to scale back multiple species, higher electrical conductivity, and lowest resistance during the charge/mass transfer processes. These properties were confirmed using Electrochemical impedance spectroscopy (EIS), Electron transfer rate constant (Ks), Mott-Schottky (MS), Double-layer capacitance (DLC), and Density-functional theory (DFT) analysis. Based on these findings Cu₂O@PANI matrix easily forms many intermediate (CO) species and maintains a higher CO₂ concentration around the electrode surface throughout the experiment. The results of the given electrocatalytic system show that the Cu₂O@PANI matrix significantly suppressed the by-product throughout the experiment, resulting in MeOH (45.21%) FE within 90 min. Given these benefits, the catalytic system is appropriate for CO₂RR.

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 this study, the effects of poly(oxy-1,2-ethanediyl), alpha-(4-nonylphenyl)-omega-hydroxy-,branched (ANP) under various concentrations on the Cu-electrodeposition on the brass surface were investigated. The leveling, grain refining, and brightening agent effects have been identified for the used ANP additive. In addition, the Cu-electrodeposits morphology was studied by Scanning Electron Microscopy (SEM) coupled with Energy dispersive X-ray analysis (EDS) and Atomic Force Microscopy (AFM). The cyclic voltammetry technique, the quantum chemical calculations, and molecular dynamics (MD) simulations were also used to explain the Cu-electrodeposition mechanism. Finally, electrochemical measurements were employed to study the ANP effect on the Cu-electrodeposit resistance in a 3.5 wt% NaCl medium. The cyclic voltammetry demonstrated that the studied system is irreversible and that the kinetics of the Cu-electrodeposition reaction are controlled by diffusion. In addition, the SEM/EDS and AFM results revealed that the ANP addition increases the Cu-electrodeposit with an improvement in its roughness degree and crystallite size. In the same context, the quantum chemical calculations and molecular dynamics (MD) simulations suggested that ANP may be strongly adsorbed on the brass and Cu-electrodeposit surfaces. Toward the end, the electrochemical measurements results indicated that the polarization resistance of the Cu-deposit increases with the presence of ANP in the copper bath, demonstrating its good corrosion resistance in marine medium.

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.

MnO has the advantages of high theoretical capacity, abundant resources and environmental friendliness, which is a potential material for lithium-ion storage. However, severe volume expansion and sluggish kinetics make MnO difficult to maintain long-term stability. In this study, MnO/C@CoPPc micro-rods composed of coral-like MnO/C nanobundles coated with CoPPc was synthesized via facile method. CoPPc impregnated into the empty space and simultaneously coated on the surface of the needles of MnO/C functions as an elastic layer to accommodate the mechanical stress caused by volume expansion of MnO/C, and simultaneously function as a buffering layer to keep electric disconnection on cycling. The volume of MnO/C is dramatically suppressed from 370% to 120%, and the reversible capacity is improved. Therefore, the configured MnO/C@CoPPc exhibits a high stability and delivers a high reversible capacity of 679.6 mAh/g after 200 cycles.

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.