Showing papers on "Supporting electrolyte published in 2021"

Elucidating the Role of Hydroxide Electrolyte on Anion-Exchange-Membrane Water Electrolyzer Performance

Abstract: Author(s): Liu, J; Kang, Z; Li, D; Pak, M; Alia, SM; Fujimoto, C; Bender, G; Kim, YS; Weber, AZ | Abstract: Many solid-state devices, especially those requiring anion conduction, often add a supporting electrolyte to enable efficient operation. The prototypical case is that of anion-exchange-membrane water electrolyzers (AEMWEs), where addition of an alkali metal solution improves performance. However, the specific mechanism of this performance improvement is currently unknown. This work investigates the functionality of the alkali metal solution in AEMWEs using experiments and mathematical models. The results show that additional hydroxide plays a key role not only in ohmic resistance of the membrane and catalyst layer but also in the reaction kinetics. The modeling suggests that the added liquid electrolyte creates an additional electrochemical interface with the electrocatalyst that provides ion-transport pathways and distributes product gas bubbles; the total effective electrochemical active surface area in the cell with 1 M KOH is 5 times higher than that of the cell with DI water. In the cell with 1 M KOH, more than 80% of the reaction current is associate with the liquid electrolyte. These results indicate the importance of high pH of electrolyte and catalyst/electrolyte interface in AEMWEs. The understanding of the functionality of the alkali metal solution presented in this study should help guide the design and optimization of AEMWEs.

Development of an electrochemical sensor for nitric oxide based on carbon paste electrode modified with Nafion, gold nanoparticles and graphene nanoribbons

Abstract: Various physiological as well as pathophysiological processes in the cardiovascular system, in the immune response or in neurotransmission depend on changes of the concentration of nitric oxide (NO). Due to the instability of this ubiquitous signal molecule in vivo and in vitro, its rapid and direct detection is necessary to obtain meaningful results. Therefore, the development of a method for the rapid electrochemical detection of nitric oxide at 0.72 V (vs. Ag/AgCl) using a carbon paste electrode, modified by drop casting, is presented. As modifying solution, a nanocomposite consisting of Nafion, graphene nanoribbons, and gold nanoparticles was prepared. The voltammetric investigations with the optimized sensor were performed at room temperature in phosphate buffer solution (0.1 M, pH 7.4) as supporting electrolyte. Based on differential pulse voltammetry measurements, the obtained results for the analytical signal showed good linear response in the range of 0.39–2.34 μ M and 2.34–104.7 μ M with a correlation coefficient of 0.9941 and 0.9984, respectively. For both linear ranges, the repeatability as well as the reproducibility was 5% and 10%, respectively. A concentration of 40 nM was determined for the detection limit, whereas the limit of quantification was 130 nM. In addition, the influence of physiological interferences was also investigated and resulted in negligible effects. Finally, the sensor was successfully used to measure the NO release of NO donors. Based on the results obtained, the new sensor provides a simple and fast method for a direct voltammetric determination of low nitric oxide concentrations in solutions.

Integration of aprotic CO2 reduction to oxalate at a Pb catalyst into a GDE flow cell configuration

Abstract: Electrochemical CO2 reduction to oxalic acid in aprotic solvents could be a potential pathway to produce carbon-neutral oxalic acid. One of the challenges in aprotic CO2 reduction are the limited achievable current densities under standard conditions, despite the increased CO2 solubility compared to aqueous applications. The application of aprotic solvents can reduce CO2 rather selectively to oxalate, and faradaic efficiencies (FEs) of up to 80% were achieved in this study with a Pb catalyst in acetonitrile, the FE being mainly dictated by the local CO2 concentration at the electrode. This process was integrated into a flow cell employing a two-layered carbon-free lead (Pb) gas diffusion electrode (GDE) and a sacrificial zinc (Zn) anode. With the application of this GDE the applicable current densities could be improved up to a current density of j = 80 mA cm−2 at a FE(oxalate) = 53%, which is within the range of the highest j reported in the literature. In addition, we provide an explanation for the deactivation mechanism of metal catalysts observed in the aprotic CO2 reduction literature. The deactivation is not related to a mass transport limitation but to cathodic corrosion observed at highly negative potential when employing quaternary ammonium supporting electrolyte cations, promoting catalyst leaching.

Electrochemistry of Thin Films with In Situ/Operando Grazing Incidence X-Ray Scattering: Bypassing Electrolyte Scattering for High Fidelity Time Resolved Studies

Abstract: Electroactive polymer thin films undergo repeated reversible structural change during operation in electrochemical applications. While synchrotron X-ray scattering is powerful for the characterization of stand-alone and ex situ organic thin films, in situ/operando structural characterization has been underutilized-in large part due to complications arising from supporting electrolyte scattering. This has greatly hampered the development of application relevant structure property relationships. Therefore, a new methodology for in situ/operando X-ray characterization that separates the incident and scattered X-ray beam path from the electrolyte is developed. As a proof of concept, the operando structural characterization of weakly-scattering, organic mixed conducting thin films in an aqueous electrolyte environment is demonstrated, accessing previously unexplored changes in the π-π peak and diffuse scatter, while capturing the solvent swollen thin film structure which is inaccessible in previous ex situ studies. These in situ/operando measurements improve the sensitivity to structural changes, capturing minute changes not possible ex situ, and have multimodal potential such as combined Raman measurements that also serve to validate the true in situ/operando conditions of the cell. Finally, new directions enabled by this in situ/operando cell design are examined and state of the art measurements are compared.

Electrochemical Behavior and Voltammetric Determination of 2-Nitrophenol on Glassy Carbon Electrode Surface Modified with 1-Amino-2-Naphthol-4-Sulphonic Acid

Abstract: 2NP is among the priority pollutants for the environmental ecosystem and poses a threat to the health of living things by mixing in wastewater Therefore, the 2NP determination is important In this study, the glassy carbon (GC) electrode surface was modified with 1-amino-2-naphthol-4-sulfonic acid (ANSA) The electrochemical behavior and voltammetric determination of 2-nitrophenol (2NP) on the modified surface (ANSA-GC) was performed Firstly, it was decided that the supporting electrolyte medium suitable for 2NP determination was Britton-Robinson (BR) buffer and the effect of pH change on the reduction peak of 2NP in this environment was investigated The effect of changing scan rate on the reduction peak of 2NP was examined and this study showed that the reduction process of 2NP on the ANSA-GC modified electrode surface was diffusion controlled process For 2NP determination,two linear working ranges with two different slopes, 119×10-6-166×10-4 M and 166×10-4-114×10-3 M were obtained LOD and LOQ values were calculated as 029 µM and 097 µM, respectively Finally, lake water was used as the real sample, and 2NP was determined in this lake water The experimental results showed that it can be used with a high accuracy and precision in the determination of 2NP with ANSA-GC modified electrode

Electrochemical conversion of pressurized CO 2 at simple silver-based cathodes in undivided cells: study of the effect of pressure and other operative parameters

Abstract: Electrochemical reduction of pressurized CO2 is proposed as an interesting approach to overcome the main hurdle of the CO2 electrochemical conversion in aqueous solution, its low solubility (ca. 0.033 M), and to achieve good faradaic efficiency in CO using simple sheet silver cathodes and undivided cells, thus lowering the overall costs of the process. The effect on the process of CO2 pressure (1–30 bar), current density, nature of the supporting electrolyte and other operative conditions, such as the surface of the cathode or the mixing rate, was studied to enhance the production of CO. It was shown that pressurized conditions allow to improve drastically the current efficiency of CO (CECO). Furthermore, at relatively high pressure (20 bars), the utilization of simple sheet silver cathodes and silver electrodes with high surfaces gave similar CECO. The stability of the system was monitored for 10 h; it was shown that at a relatively high pressure (15 bar) in aqueous electrolyte of KOH using a simple plate silver cathode a constant current efficiency of CO close to 70% was obtained.