ChemElectroChem最新文献

Industrial applications of microbial electrochemical systems will require regular maintenance shutdowns, involving inspections and component replacements to extend the lifespan of the system. Here, we examined the impact of such shutdowns on the performance of three electrode materials (i. e., platinized titanium, graphite, and nickel) as cathodes in a microbial electrochemical system that would be used for electromethanogenesis in power-to-gas applications. We focused on methane (CH₄) production from hydrogen (H₂) and carbon dioxide (CO₂) using Methanothermobacter thermautotrophicus. We showed that the platinized titanium cathode resulted in high volumetric CH₄ production rates and Coulombic efficiencies. Using a graphite cathode would be more cost-effective than using the platinized titanium cathode in microbial electrochemical systems, but showed an inferior performance. The microbial electrochemical system with the nickel cathode showed improvements compared to the graphite cathode. Additionally, this system with a nickel cathode demonstrated the fastest recovery during a shutdown experiment compared to the other two cathodes. Fluctuations in pH and nickel concentrations in the catholyte during power interruptions affected CH₄ production recovery in the system with the nickel cathode. This research enhances understanding of the integration of biological and electrochemical processes in microbial electrochemical systems, providing insights into electrode selection and operating strategies for effective and sustainable CH₄ production.

In their Research Article, Johannes Kästner and co-workers provide a theoretical basis for the study of a system with respect to its redox and acid/base properties and represent the results by redox-acid/base phase diagrams. As this approach provides access to all properties associated with the system′s free-energy profile, not only the stability of species under different conditions but also kinetic quantities can be depicted. The diagrams can be constructed based on both experimental and computational data, thus bridging experiment and simulation (DOI: 10.1002/celc.202400301).

Thermal treatments are commonly used to improve electrode kinetics in vanadium redox flow batteries (VRFB). The impact of the widely adopted thermal treatment—400 °C for least 24 hours—was investigated on polyacrylonitrile (PAN)-based continuous carbon filaments (tows) and compared to PAN-based graphite felts. Surface properties were assessed with scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and wettability measurements. The electrode activity was investigated via electrochemical impedance spectroscopy (EIS). Charge-transfer resistances and the constant phase element parameters related to the electric double layer were determined, revealing a correlation between enhanced electrode activity and increased double layer across all electrodes. An 8-hour 400 °C thermal treatment was sufficient to improve electrode activity for tows, whereas felts required longer durations, up to 24 hours, attributed to differences in the carbonization process employed for each material, with the tows undergoing continuous processing and the felts following a batch process. Three-electrode half-cell EIS measurements were conducted to elucidate positive and negative electrode contributions. Activated continuous carbon filament electrodes exhibited consistent electrode activities in both the catholyte (VO₂⁺/VO²⁺) and anolyte (V³⁺/V²⁺), whereas the electrochemical activity of felts was limited by the electrode deactivation in the anolyte.

Synthetic cocaine analogs are designer drugs that recently emerged as non-controlled substitutes for their parent drug. Among them, nitracaine is of particular concern for its psychoactive effect. In this work, we present a thorough characterization of the electrochemical behavior of nitracaine, with a final quantification performed by differential pulse voltammetry (DPV) in ethanol/lithium perchlorate 0.1 M. The selectivity of the method and reproducibility of results were assessed. LOQ of 0.3 μg mL⁻¹ and a linear dynamic range of up to 400 μg mL⁻¹ were obtained. In addition, recoveries from 85 % to 101 % were achieved on both simulated and real samples. For nitracaine analysis in urine, a clean-up and a preconcentration step by solid phase extraction (SPE) using the adsorbent Florisil have been developed and optimized through the Design of Experiments (DoE) strategy, thus achieving an enrichment factor of 20.

Electrodes, which offer sites for mass transfer and redox reactions, play a crucial role in determining the energy efficiencies and power densities of redox flow batteries. This review focuses on various approaches to enhancing electrode performance, particularly the methods of surface etching and catalyst deposition, as well as some other advanced strategies for regulating electrode surface properties. These approaches aim to increase active sites and enhance kinetics for the redox reactions, which are crucial for elevating power density and electrolyte utilization, eventually determining the performance of the flow battery. Highlighting the need for interdisciplinary research, this mini-review suggests that future advancements in electrode design will significantly impact the commercial viability and adoption of redox flow batteries in sustainable energy storage solutions.

The rapid depletion of fossil fuels and the change from conventional energy supply to so-called sustainable and renewable energy sources have led to a renaissance of electrochemical, photochemical, and photoelectrochemical methods for chemical synthesis. While drastic experimental improvements have been realized in recent years, systematic computational studies of these types of reactions are, however, rather limited caused by a lack of suitable representations. Herein we present a generalized method to investigate and analyze a chemical system with respect to its redox- and acid/base-properties based on Gibbs free-energy differences. We represent the results in a clear manner by means of redox−acid/base phase diagrams. Motivated by computational needs, the presented method is a direct link between experimentally measurable values and Gibbs free-energy profiles, connecting experiment and simulation. Thus, it serves as an entry to systematic computational studies of reactions, which involve a combination of electron transfers and acid/base-chemical reaction steps, because it enables the representation of both thermodynamic and kinetic properties. The presented method is applied to four exemplary systems: Phenol, dicobaltocenium amine as a proton-coupled electron transfer (PCET) reactant, and two porphyrin Ni^II catalysts for the electrocatalytic hydrogen evolution reaction (HER).

Redox flow batteries (RFBs) are an attractive choice for stationary energy storage of renewables such as solar and wind. Non-aqueous redox flow batteries (NARFBs) have garnered broad interest due to their high voltage operation compared to their aqueous counterparts. Further, the utilization of bipolar redox-active molecules (BRMs) is a practical way to alleviate crossover faced by asymmetric RFBs. In this work, ferrocene (Fc) and phthalimide (PI) are covalently linked with various tethering groups which vary in structure and length. The compiled results suggest that the length and steric shielding ability of the linker group can greatly influence the stability and overall performance of Fc-n-PI BRM-based NARFBs. Primary sources of capacity loss are found to be BRM degradation for straight chain spacers <6 carbons and membrane (Nafion) fouling. Fc-hexyl-PI provided the most stable battery cycling and coulombic efficiencies of >98 % over 100 cycles (~13 days). NARFB using Fc-hexyl-PI as an active material exhibited high working voltage (1.93 V) and maximum capacity (1.28 Ah L⁻¹). Additionally, this work highlights rational strategies to improve cycling stability and optimize NARFB performance.

In the development of polymer electrolytes, the understanding of the complex interplay of factors that affect ion transport is of importance. In this study, the strongly coordinating and flexible poly (ethylene oxide) (PEO) is compared to the weakly coordinating and stiff poly (trimethylene carbonate) (PTMC) as opposing model systems. The effect of molecular weight (M_n) and end group chemistry on the physical properties: glass transition temperature (T_g) and viscosity (η) and ion transport properties: transference number (T₊), ion coordination strength and ionic conductivities were investigated. The cation transference number (T₊) showed the opposite dependence on M_n for PEO and PTMC, decreasing at low M_n for PTMC and increasing for PEO. This was shown to be highly dependent on the ion coordination strength of the system regardless of whether the end group was OH or if the chains were end-capped. Although the coordination is mainly of the cations in the systems, the differences in T₊ were due to differences in anion rather than cation conductivity, with a similar Li⁺ conductivity across the polymer series when accounting for the differences in segmental mobility.

This work investigates the application of poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) with polyethylene oxide (PEO) in lithium batteries (LIBs). This composite film comprising PEDOT:PSS and PEO was 3D printed onto a carbon nanofiber (CNF) substrate to serve as a layer between the polypropylene (PP) separator and the lithium anode in LIBs. The resulting CNF-PEDOT:PSS-PEO film exhibited superior mechanical and thermal properties compared to conventional PP separators. Mechanical tests revealed a high Young's modulus and puncture strength for the composite film. Thermal stability tests indicated that the CNF-PEDOT:PSS-PEO film remained stable at higher temperatures compared to the commercial PP separator, and combustion tests confirmed its superior fire-resistance properties. In terms of conductivity, the composite film maintained comparable ionic conductivity to the commercial PP separator. Electrochemical tests demonstrated that LIBs incorporating the CNF-PEDOT:PSS-PEO film exhibited slight improvement in cycling performance, with a 7.9 % increase in long-term cycling capacity compared to LIBs using only the commercial PP separator. These findings indicate that the developed CNF-PEDOT:PSS-PEO composite film holds promise to improve safety, while maintaining the electrochemical performance of LIBs by reducing dendrite formation and enhancing thermal stability.

The Front Cover illustrates a chemical sensor based on an extended-gate-type organic field-effect transistor (OFET) as a running machine and a runner′s sportswear. The target glucose contained in the runner′s sweat at micromolar levels is an important biomarker that can be collected painlessly. As shown on the front display of the running machine, the OFET-based chemical sensor successfully detects the target sweat glucose with high sensitivity. More information can be found in the Research Article by Tsuyoshi Minami and co-workers (DOI: 10.1002/celc.202400292).