[en] In molten carbonate thermo-electrochemical cells (thermocells), the dispersion of solid oxide in the molten electrolyte was found to improve conditions of thermoelectric energy conversion. However, stability of the solid oxide in eutectic (Li,Na)₂CO₃ electrolyte is crucial. The change in cell performance, due to compositional changes in the electrolyte mixture using various selected solid oxides, was studied. The solid oxides of Al₂O₃ or LiAlO₂ were chemically reactive and no stable cell potential was observed when these compounds were added compared to when solid MgO or CeO₂ were added. Also, a solid MgO-dispersion in the electrolyte delivered a larger Seebeck coefficient of −1.8 mV/K, favoring this oxide all together. The impact of the surface area of solid grains of MgO on the cell performance was investigated. From the electrical (σ) and thermal (λ) conductivity of the electrolyte mixture, along with the measured Seebeck coefficient (α_s), the figure of merit (ZT) was determined. In addition to having a high stability, the dispersion of solid MgO with large surface area provided a better (σ/λ) ratio, and a larger α_s (-1.8 mV/K) as well as ZT (1.1).

[en] Highlights: • The deactivation was due to coating loss or combined with passivation of the titanium substrate. • The coating loss was occurring as coating dissolution, coating spalling and coating peeling off. • No critical value of the amount of the residual iridium was found in this work to predict the eventual deactivation before forming the passive oxide film. • Deactivation of the anodes was found to be more dependent on the calcination temperature than other manufacturing parameters. -- Abstract: In this work, series of IrO₂-Ta₂O₅ anodes were investigated. The catalytic activity towards oxygen evolution reaction (OER) of these anodes are determined by calcination temperature, coating loading (coating thickness), pretreatment of titanium substrate and coating method. The difference in OER performance among the anodes are ascribed to the crystallinity of the IrO₂ phase and the phase composition of the coatings. The durability of the anodes were also studied by conducting an accelerated lifetime test (ALT) in acidic 0.9 mol L⁻¹ Na₂SO₄ solution at a current density of 5 kA m⁻². An anode prepared at a moderate temperature exhibits an excellent lifetime of almost one year although its catalytic activity is not the best. Nevertheless, using the electrostatic spraying method to replace the hand-brush method in the coating preparation can prolong the service life even further and with less amount of coating loading. Moreover, it reveals that the coating loss or combined with titanium substrate passivation results in the eventual deactivation of the anodes during ALT. No critical value of the amount of the residual iridium was found in this work to predict the eventual deactivation before forming the passive oxide film. In addition, the deactivation of the anodes strongly depends on the calcination temperature.

[en] Electrochemical studies, mainly cyclic voltammetry, square wave voltammetry and chronoamperometry, were carried out to study the behavior of dissolved silicon species in molten LiF-KF with additions of K₂SiF₆ at temperatures from 550 to 800 °C. Electrolysis experiments were run at constant current to deposit pure silicon. Working electrodes of silver, tungsten and glassy carbon and cathodes of silver and silicon were used. The cathodic reduction of dissolved Si (IV) species to silicon was found to be diffusion controlled. Some influence of nucleation phenomena was observed on silver cathode substrates. High purity and good quality silicon deposits were obtained during galvanostatic electrolysis. One challenge is to reduce the inclusions of solidified electrolyte. Current efficiencies for silicon deposition were found to be in the range from 85 to 95%

[en] Ni(OH)₂/AC/CNT composite has been prepared via a green rapid microwave assisted method in an ethylene glycol medium. Scanning electron microscopy images show that Ni(OH)₂ nanoparticles, activated carbon spheres and nanotubes constructed a three-dimensional (3-D) connected network, which lead to a high specific capacitance 1038 F g⁻¹ at current density of 1 A g⁻¹. Based on Ni(OH)₂/AC/CNT composite as positive electrode material and activated carbon as negative electrode material, an asymmetric supercapacitor of AC//Ni(OH)₂/AC/CNT was fabricated. The unit supercapacitor demonstrates excellent electrochemical performances using non-woven fabric as separator and 6 M KOH as electrolyte within 1.6 V operation window. The maximum specific capacitance of 82.1 F g⁻¹ is achieved at 0.5 A g⁻¹ and the energy density can reach up to 32.3 Wh kg⁻¹ at power density of 504.8 W kg⁻¹. Furthermore, 83.5% capacitance retention is obtained after 1000 charge-discharge cycles. These results indicate that the AC//Ni(OH)₂/AC/CNT supercapacitor is promising to be applied in a practical device for energy storage devices.