ChemElectroChem最新文献

There have been significant advancements in the electrosynthesis of fuels and organic molecules, making it an increasingly sustainable and cost-effective alternative to traditional chemical redox reagents. Early versions of these systems faced challenges in chemoselectivity due to high applied overpotentials, which have been mitigated with the introduction of molecular electrocatalysts, like metal salens (MSalens). These MSalens reduce the required overpotentials, increase turnover numbers (TON), and have simple modularity within their ligand structure allowing for tunable selectivity. While these MSalen electrocatalysts are typically used homogeneously for engineering simplicity, downstream separations are often costly and time-consuming. Immobilization of MSalens addresses these issues by enabling synthesis at lower potentials, achieving high selectivity, and facilitating straightforward separations. This review explores the application of MSalens in electrosynthesis and immobilized molecular electrocatalysts in organic electrosynthesis.

N. Thissen, J. Hoffmann, S. Tigges, D. A. M. Vogel, J. J. Thoede, S. Khan, N. Schmitt, S. Heumann, B. J. M. Etzold, A. K. Mechler, ChemElectroChem 2024, 11, e202300432. https://doi.org/10.1002/celc.202300432

After publication, the authors have successfully uploaded the data associated with this publication to the Zenodo platform. Therefore, the data availability statement has been changed to ensure that readers and researchers can easily access the dataset.

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Data Availability Statement

The raw data is made available in the Zenodo repository and can be accessed here: https://doi.org/10.5281/zenodo.12582471

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Aqueous zinc-ion batteries (AZIBs) have garnered significant attention as next-generation energy storage systems. However, developing high-energy-density cathode materials remains a critical challenge. Organic compounds with multi-electron transfer processes offer a promising solution to this issue. In this concept, we outline the fundamental structural principles and mechanisms underlying multi-electron transfer of redox-active organic compounds. We categorize various organic cathode materials into n-type, p-type, and bipolar compounds, and discuss their structural features, redox chemistry, and capacity performance in AZIBs by analyzing cyclic voltammetry profiles and charge storage mechanisms. Our goal is to offer valuable insights into the molecular design and redox chemistry of multi-electron transfer organic compounds to achieve high-performance AZIBs.

In this study, Li₄Ti₅O₁₂ (LTO) and TiO₂ nanocomposites uniformly were synthesized on the heat-treated graphite felt through (HGF) hydrothermal and heat treatment methods, denoted by LTO/TiO₂@HGF, which LTO/TiO₂@HGF acts as effective electrocatalysts to enhance the electrochemical activity in vanadium redox flow battery (VRFB) systems. The cyclic voltammetry (CV) curves of the LTO/TiO₂@HGF show higher peak current densities and smaller peak separation than TiO₂@HGF, HGF, and pristine graphite felt (PGF) for catalyzing V²⁺/V³⁺ and VO₂⁺/VO²⁺, indicating superior electrochemical activity of LTO/TiO₂@HGF. The VRFB using LTO/TiO₂@HGF as the positive and negative electrodes demonstrates an energy efficiency of 82.89 % at 80 mA cm⁻². When the VRFB using LTO/TiO₂@HGF is applied by a high current density of 200 mA cm⁻², it still shows an energy efficiency of 62.22 %. However, the VRFB using PGF cannot perform any performance, and the VRFB using HGF only performs 51.94 %. This improvement can be attributed to the uniform distribution of LTO/TiO₂ nanowires on the surface of the graphite felt and the presence of oxygen vacancies on LTO/TiO₂, which increased the number of active sites for vanadium ion absorption.

Electrochemical CO₂ reduction has attracted significant attention as a potential method to close the carbon cycle. In this study, we investigated the impact of the electrode fabrication and electrolysis conditions on the product selectivity of Ag electrocatalysts using a machine learning (ML) approach. Specifically, we explored the experimental conditions for obtaining the desired H₂/CO mixture ratio with high CO efficiency. Notably, unlike previous ML-based studies, we used experimental results as training data. This ML-based approach allowed us to quantitatively assess the effect of experimental parameters on these targets with a reduced number of experimental trials (only 56 experiments). An inverse analysis based on the ML model suggested the optimal experimental conditions for achieving the desired characteristics of the electrolysis system, with the proposed conditions experimentally validated. This study constitutes the first demonstration of optimal experimental conditions for electrochemical CO₂ reduction with desired characteristics using the experimental results as training data.

Advanced fluorinated proton-conducting membrane are dominating functional macromolecules due to their high performance in electrochemical energy devices. However, the co-ion leakage and low power densities still proposes a challenge. Herein, a novel functionally tailored polyvinylidene fluoride-co-(γ)-sulfopropyl acrylate (PVDF-g-SA) based proton-conducting membrane is prepared for vanadium redox flow batteries (VRFBs). The approach introduces a facile guideline to design halato-telechelic −SO₃H architectures by tethering γ-sulfopropyl acrylate onto dehydrofluorinated PVDF. The optimized PVDF-g-SA-15 exhibits proton conductivity (κ_m^H+) of 17 mS cm⁻¹ (akin Nafion: ~19 mS cm⁻¹) and retained 87 % and >95 % of its properties in Fenton's reagent and 3 M H₂SO₄, respectively. In VRFB device, the PVDF-g-SA-15 shows ∼98 % capacity utilization outperforming Nafion-117 (∼85 %). Moreover, bearing dense ionic orientation (viz AFM phases), the potential drop rate is ~2× lower for PVDF-g-SA-15 (1.4×10⁻³ V min⁻¹) than that of Nafion-117 (2.6×10⁻³ V min⁻¹). Operational endurance is evaluated fit for 150 mA cm⁻² showing maximum coulombic, energy and voltage efficiencies of >98 %, ∼78 %, ∼80 %, respectively. Further investigation for ~200 cycles infer excellent durability with ∼95 % property retention. Additionally, the PVDF-g-SA-15 can deliver ~20 % higher power density than Nafion-117 does. Thus, the revealed alternate membrane holds promising utility in VRFB applications.

This work reports the fabrication of p-type Si micropillar (MP) substrates decorated with Ag_xCu_100−x bimetallic nanoparticles and their application as photocathodes for CO₂ photoelectrochemical reduction. Metal deposition by metal-assisted chemical etching is chosen as the nanoparticle synthesis method, to explore for the first time its capabilities for 3D structures. It is found to be applicable, allowing a good control of the composition, with nanoparticles distributed along the entire MP, but with a coverage gradient from top to bottom. The Ag_xCu_100−x decorated Si MPs photocathodes show enhanced light trapping compared to flat Si, with 45 % lower reflectance values in the visible and significantly higher catalytic activity, in terms of photocurrent density, overpotential and power savings (4.7 % for Ag₅₀Cu₅₀/Si MPs vs. 3 % for Ag₅₀Cu₅₀/flat-Si). Si MPs coated with Ag₅₀Cu₅₀ and Ag₂₀Cu₈₀ provide the highest gain in potential (440 and 600 mV vs. bare Si MPs) and an increased selectivity towards high energy density products (i. e., CH₄) compared to monometallic photocathodes. These are promising features for efficient light-driven CO₂ conversion. However, a significant metal loss is observed during photoelectrolysis, especially for Cu-rich compositions. Suggestions to improve the photocathode performance in terms of metal coating homogeneity and catalyst stability are presented.

There has been an increased effort to replace the expensive and rare platinum and platinum group metals to speed up the sluggish oxygen reduction reaction (ORR) kinetics, which limits the efficiency of fuel cells. One class of promising Pt-alternative catalysts for ORR is metal-free halogen-doped carbon materials. Herein, bromine-doped and iodine-doped graphene were synthesized via mechanochemical activation. The synthesized samples exhibited sub-rounded particles. Mechanical activation via ball milling increased the specific surface area of graphene by reducing particle size. Ball milling also enhanced dopant dispersibility and increased surface roughness, though it reduced surface area compared to ball-milled graphene, likely due to the size difference between carbon and halogen atoms. Among the synthesized catalysts, iodine-doped graphene exhibits the highest limiting current density of 1.806 mA cm⁻² with the highest ORR onset potential of 0.74 V vs reversible hydrogen electrode (RHE). The iodine-doped graphene also showed good stability after 1000 cycles of accelerated degradation test. The enhanced ORR performance of iodine-doped graphene was reached using the optimized iodine-to-graphene mass ratio of 4 : 1 after 48 h ball milling time.

This study focuses on enhancing lithium-sulfur (Li−S) battery performance by using nickel(II) oxide (NiO), as polysulfide adsorbent to mitigate the shuttle effect. Polysulfides have been shown to effectively adsorb onto the hydrophilic surfaces of polar metal oxides and thus suppress this effect. In this work, a NiO – reduced Graphene Oxide/Sulfur (NiO-rGO/S) hybrid composite paper was developed for use as a binder-free, flexible cathode. The characterization of the composite films was done through Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, thermogravimetric analysis (TG), field emission gun scanning electron microscopy (FEG-SEM), energy dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD). To test adsorption of polysulfides by NiO, ultraviolet-visible (UV-Vis) spectroscopy was applied. Electrochemical performance tests of CR2032 cells were also conducted by cyclic voltammetry (CV), charge-discharge tests, electrochemical impedance spectroscopy (EIS). The NiO-rGO/S cathode, particularly the one containing 2 % NiO, exhibited remarkable performance. It delivered an initial discharge capacity of 1230 mAh g⁻¹, maintaining 1029 mAh g⁻¹ after 300 cycles, with a high capacity retention of 83.1 %. This suggests that the NiO-rGO/S hybrid composite is a promising candidate for improving the efficiency and lifespan of Li−S batteries.

The front cover shows a karate fighter who is supposed to represent our electrodes system. She kicks into water and splits the water into O₂ and H₂ bubbles. The feet with which she splits the water are “coated” with our catalyst material NiFe LDH. The same schematic of LDH as in the article was used to illustrate the structure giving reference to our article. Her fists glow with electricity. A wind turbine can be seen in the background to emphasize that green electricity is being used. The woman is standing in a mineral cave and a mineral is shown at the bottom left, which is intended to establish a link to borate/borax minerals. More information can be found in the Research Article by Regina Palkovits and co-workers (DOI: 10.1002/celc.202400457).