Production of Al-Sc Alloy by Electrolysis from Cryolite Melt Using Secondary Feedstock Material

Electrolysis experiments to produce Al-Sc alloys were carried out in galvanostatic mode using a cryolitic melt with a NaF/AlF3 molar ratio of 2.2 at 980 °C, using both synthetic and waste feeds. After elucidation of the cryolite electrolyte bath chemistry when adding Sc2O3, small-laboratory scale trials allowed for the demonstration of the process and the study and for the optimisation of the electrolysis parameters. Experiments in large-scale electrolysis cells allowed us to run long-term trials in continuous operation, while the on-line monitoring of the cell off-gases ensured the environmentally benign performance of the process. The aluminium product obtained contained 0.6–2.6 wt% Sc, depending on the current density applied. The material is suited to prepare Al-Sc master alloys for 3D printing powders.

Modeling galvanostatic charge–discharge of nanoporous supercapacitors

Molecular modeling has been considered indispensable in studying the energy storage of supercapacitors at the atomistic level. The constant potential method (CPM) allows the electric potential to be kept uniform in the electrode, which is essential for a realistic description of the charge repartition and dynamics process in supercapacitors. However, previous CPM studies have been limited to the potentiostatic mode. Although widely adopted in experiments, the galvanostatic mode has rarely been investigated in CPM simulations because of a lack of effective methods. Here we develop a modeling approach to simulating the galvanostatic charge–discharge process of supercapacitors under constant potential. We show that, for nanoporous electrodes, this modeling approach can capture experimentally consistent dynamics in supercapacitors. It can also delineate, at the molecular scale, the hysteresis in ion adsorption–desorption dynamics during charging and discharging. This approach thus enables the further accurate modeling of the physics and electrochemistry in supercapacitor dynamics.

Mathematical Modeling of the Phenomenon of Space-Charge Breakdown in the Galvanostatic Mode in the Section of the Electromembrane Desalination Channel

One of the ways to increase the efficiency of the desalination process in membrane systems is to use intensive current modes. Recently, the phenomenon of space-charge breakdown was theoretically described for desalination under intensive current modes. The space-charge breakdown is a decrease in the magnitude and size of the extended space charge regions (SCRs) of opposite signs, formed at the cation- and anion-exchange membranes in the desalination channel, when they approach each other. Therefore, this phenomenon negatively affects the intensity of electroconvection and the efficiency of mass transfer in membrane systems. We report the results of the first theoretical analysis of the space-charge breakdown in the galvanostatic electric mode, which is generally used in the research and operation of membrane systems. For this purpose, a one-dimensional model of the ion transfer of the electrolyte solution in the section of the desalination channel at the direct current is developed. The regularities of changes in the extended SCRs in the galvanostatic mode are determined. A relation is obtained for the onset time of the space-charge breakdown, which makes it possible to determine the parameters of the effective operation of the membrane system.

Modeling galvanostatic charge-discharge of nanoporous supercapacitors

Molecular modeling can study the energy storage of supercapacitors at the atomistic level and has become indispensable in this research. The constant potential method (CPM) allows keeping the electric potential uniform on the electrode, which is essential for a realistic description of the charge repartition and dynamics process in supercapacitors. Prior CPM studies have been limited to the potentiostatic mode. Though widely adopted in the experiment, the galvanostatic mode has been rarely investigated in CPM simulations due to a lack of effective methods. In this work, we developed a modeling approach to simulating the galvanostatic charge-discharge of supercapacitors under constant potential (GCD-CPM). We show that, for nanoporous electrodes, GCD-CPM can capture supercapacitor dynamics in excellent agreement with experimental measurements and delineate the ion adsorption-desorption dynamics underlying the hysteresis with molecular resolutions during charging and discharging. Therefore, this GCD-CPM modeling could open up new avenues for exploring the rich physics and electrochemistry of supercapacitor dynamics.

Mesoporous oxide films grown on Sn foil using various anodizing modes in alkaline electrolyte

The mesoporous structures of tin oxide were obtained by a simple method of one-stage electrochemical anodizing of Sn foil in 1M NaOH in various anodizing modes. Anodizing in the pulse potentiostatic mode allowed determination of actual value of the voltage drop on the anode. For the first time the possibility of obtaining mesoporous oxide films on the surface of tin using galvanostatic mode of anodizing was demonstrated. It was found that the surface morphology of the obtained tin oxide layers is strongly dependent on the anodizing mode. Based on the data obtained, a two-stage mechanism was proposed for the growth of porous structures on the surface of tin in the galvanostatic mode including initial formation of the layer of SnO·xH2O which is subsequently oxidized to SnO2·xH2O mesoporouslayer.