Electrochemistry Communications最新文献

Preventing the accumulation of water in the gas diffusion layer (GDL) proves effective in enhancing the performance of polymer electrolyte fuel cells (PEFCs). To understand the water transport phenomena in GDLs and channels of PEFCs, cell hardware for operando synchrotron X-ray radiography was developed with a 100 mm channel length, facilitating the separate quantification of liquid water in the cathode and anode GDLs. The presence of liquid water in the cathode and anode GDLs was confirmed during operation with a supply of dry gas in a counter-flow configuration. Furthermore, the amount of liquid water in the cathode and anode GDLs increased toward the cathode inlet, while the amount of water in the cathode and anode channel regions increased toward each outlet. The liquid water distribution in the GDLs along the channel direction can be attributed to water transport from cathode to anode (back-diffusion), decreasing toward the anode outlet. Therefore, conducting radiography experiments aligned parallel to the GDLs and perpendicular to the channel could provide valuable insights for a more comprehensive understanding of water transport in cells.

The oxygen evolution reaction (OER) on the TiO₂ surface at the solid–liquid interface was observed in real-time and operando using fluorescence-yield X-ray absorption spectroscopy (XAS) in the soft X-ray region. The OER was observed during a potential sweep with UV light on or off, focusing on the oxygen K-edge XAS. Although conventional XAS measurements require long measurement times, the spectra during the reaction were obtained every 3 s in the present experiment via wavelength-dispersive XAS technique. An increase in the X-ray absorption intensity at approximately 533.8 eV was observed during the potential sweep only with UV light on. The observed spectral change is discussed in relation to the reaction mechanism of the OER. The present technique can be applied to a wide range of analyses of (photo-) electrocatalysis and electrochemical reactions at solid–liquid interfaces to observe their products and intermediates during the reaction.

The development of MXenes using Lewis acidic salts for etching (MS-MXenes) in molten salts presents a novel, fluorine-free method attracting considerable interest. However, the behavior of various MS-MXenes and their derivatives in aqueous environments remains largely unexplored. Particularly, vanadium-based MXenes demonstrate intriguing properties in Zn ion aqueous electrolytes. Herein, a fluorine-free V₂CT_x MXene@VO_x is synthesized by molten salt etching under an argon atmosphere. The electrochemical properties of V₂CT_x@VO_x are tested in various aqueous electrolytes, including Zn(TFSI)₂, ZnSO₄, ZnBr₂, ZnAc₂, and ZnCl₂ solutions. The V₂CT_x@VO_x shows high redox capacities in all these Zn ion electrolytes, with the peak performance observed in 1 M ZnBr₂, achieving a maximum capacity of 172 mAh g⁻¹ at 1 mV s⁻¹. This performance rivals that of V₂CT_x MXene prepared through wet-chemical methods. These results underscore the potential of MS-MXenes materials in aqueous energy storage applications.

In this work, we conduct a detailed study to understand the photoelectrochromic properties of Al-Pt co-doped tungsten oxide (WO₃). Similarly, we support the photoelectrochromic findings with material characterization, providing additional understanding of the photoelectrochromic performance exhibited by the prepared samples. Additionally, we discuss the effects of Al and Pt doping on photoelectrochromic performance in detail, with a focus on X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) combined with EDS, X-ray photoelectron spectroscopy (XPS), and optical transmittance. XRD peaks confirm the presence of hexagonally-structured WO₃ in the prepared samples with a polycrystalline nature, and a similar observation is confirmed via TEM analysis. Surface characterizations conducted through SEM and EDS analyses unveil the morphologies and particle sizes. Optical studies show a bandgap of 1.88 eV and 1.95 eV for Al doped and Al-Pt co-doped WO₃, indicating bandgap shrinkage in comparison to the optical bandgap of WO₃ of 2.36 eV. The Al-Pt co-doping results in a significant enhancement in photoelectrochromic performance, attaining an optical modulation of 43.61 % at 550 nm and consequently 85 % of the initial transmittance recovered after 2 h of bleaching in the dark. This is an improvement in comparison to the Al doped sample which attains a coloration depth of 43.15 % at 550 nm with only 75 % of the original transmittance being recovered after 2 h under dark conditions.

Semi-transparent platinum electrodes were designed and optimized to implement photoluminescence (PL) and electrochemiluminescence (ECL) in microchannels under flow conditions. The luminescence properties of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) were used to map steady-state emitted light through semi-transparent microchannel electrodes. Several diffusive-convective regimes were thus imposed in order to experimentally highlight the operating conditions of the electrodes, in particular the active zones at their upstream edges contributing to the Faradaic current. PL and ECL profiles were established on the electrode surfaces as a function of flow rate. The PL profiles confirmed the control of the process by mass transport. The data were validated by numerical simulations within the limits of experimental accuracy. ECL emission in presence of the co-reactant tri-n-propylamine (TPA) was also limited by mass transport. However, in comparison the characteristics of the ECL profiles demonstrated the complexity of the underlying mechanism involving Ru(bpy)₃²⁺ regeneration and TPA consumption.

The fraudulent practice of adding ammonium salts to milk in order to enhance the nitrogen content has serious health implications including renal failure. Ammonium ion detection has been targeted through the conventional analytical methods however, lack of portability and complex operation limits their use for field applications. In this scenario, paper-based test strips and electrochemical sensors can provide strategies for point-of-test applications. Here, an ion-selective paper-based chromogenic strip and an electrochemical sensor has been developed for detection and quantification of ammonium ions. The developed paper-based chromogenic strip showed detection limit of 0.008 % (w/v) for ammonium ions, whereas, electrochemical sensor showed an LOD of 0.0062 ± 0.0023 % (w/v) with a sensitivity of 1.6 × 10⁻⁵ A.% ⁻¹.mm⁻². The developed paper-based chromogenic strip and electrochemical sensor can be employed by regulatory bodies and dairy industries to ensure the safety and quality of milk.

Improving lithium-ion transport in electrodes by controlling electrode microstructure is a promising option for enhancing the fast-charging capability of graphite anodes in lithium-ion batteries. Dry processing of electrodes based on a polytetrafluoroethylene binder has attracted considerable attention as an alternative to solvent-based wet processing. The morphology of graphite particles has a significant impact on electrode microstructure, but few reports have been published on dry-processed graphite anodes. In this work, we found that the morphology of graphite particles is a key factor to determine the fast-charging capability of the dry-processed graphite electrode as well as the microstructure of the dry-processed graphite electrode. X-ray microscopy combined with mercury porosimetry and symmetrical cell electrochemical impedance spectroscopy reveal that the difference in porosity between the top and bottom layers of a dry electrode with spherical graphite particles is greater than that of flake-shaped graphite particles, resulting in enhanced lithium-ion transport in the electrode and improved fast-charging capability at a high charging rate of 5C (17.5 mA cm⁻²). These findings supply insights into the effective design of dry-processed graphite anodes with an emphasis on fast-charging capability as well as the development of graphite anode materials for dry-processing based lithium-ion batteries.

Rechargeable zinc-air batteries have been identified as promising technologies for energy storage. However, developing cost-effective electrocatalysts that can efficiently facilitate the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for their advancement. This work investigates synthesized electrocatalysts composed of graphene-Cu₂O deposited on carbon cloth by doctor blading casting method as bifunctional electrodes in a rechargeable Zn-air battery. The battery integrated with graphene-Cu₂O as the air-cathode electrocatalyst showed superior performance in terms of cycling stability compared to that without Cu₂O. This enhanced performance is attributed to the reversibility of Cu⁺/Cu²⁺ species during the redox reactions facilitated by the high electrical conductivity of graphene. Therefore, the results suggest the potential of the synthesized electrodes for advancing the development of rechargeable Zn-air batteries.

This study provides a unique electrochemical sensor that exhibits both excellent sensitivity and selectivity, while also being environmentally friendly. The CuAl-LDH/GCE sensor, proposed as the recommended sensor, was synthesized using a straightforward one-step co-precipitation procedure. It was first used to measure dopamine levels using differential pulse voltammetry. At the ideal pH level of 8, dopamine has a positive charge, but ascorbic acid and uric acid have a negative charge. LDH, on the other hand, carries a negative charge and exhibits high electrostatic attraction towards dopamine, but is electrostatically repelled by negatively charged ascorbic acid and uric acid. Hence, CuAl-LDH/GCE has the potential to specifically ascertain the existence of dopamine in the presence of these particular species. The examination of the composition and morphology of CuAl-LDH was conducted using various analytical techniques, including scanner electron microscopy (FESEM), transmission electron microscope (TEM), element mapping (MAP), Fourier transform infrared (FTIR), energy-dispersive X-ray spectroscopy (EDX), Brunauer Emmett Teller (BET), X-ray photoelectron diffraction (XRD), and Raman techniques. Under ideal circumstances, the calibration graph of dopamine was generated using differential pulse voltammetry. A linear range of 4.194–1151.54 μM was achieved for dopamine, with a limit of detection of 0.33 μM. The findings of the study indicate that the sensor created for dopamine determination has exceptional stability, repeatability, and reproducibility. The sensor that was presented was effectively used for the measurement of dopamine in both pharmaceutical ampoules and human plasma samples.

The voltammetric response of microparticulate deposits resulting from the evaporation of ethanolic extracts of leaves of Ginkgo biloba L. trees in contact with aqueous acetate buffer has been studied. Voltammetric data associated with the oxidation of polyphenolic secondary metabolites permits the discrimination of individuals by sex and age. Evaluation of age variation of reactivity with reactive oxygen species (ROS) was also described.