Search

The present simplified electrochemical model of a horizontal upward-facing Zn anode combined with a Ni(OH)2/NiOOH cathode thus reasonably simulates the time-dependent coupling phenomena between the electrode surface morphological variations and the ionic mass transfer rate inside the model-pore mesoporous microstructure that extends across the width of a Zn battery cell.

Electrochemical processes such as electrodeposition and two-phase electrolysis involves numerous transport and reactivity coupled phenomena. Concerning the associated reactive problem which involves numerous kinetic constants, not always all identified, the mathematical problem is stiff. The present paper shortly presents the idea developped in more extended papers of species profiles calculation under the partial local thermodynamical equilibrium. Strategy and algorithms are given here with the use of the zinc oxide deposition process example.

The binding state of Si in films electrodeposited in trimethyl-n-hexylammonium bis(trifluoromethylsulfonyl)imide containing 0.1 mol L[?]1 SiCl4 was investigated by means of X-ray photoelectron spectroscopy (XPS). The bombardment of Ar+ mainly causes the transition of spectrum shape from bimodal to broad in XPS spectra of Si 2p core level when Ar+ etching is conducted. Angle-resolved XPS confirmed that the bimodal spectrum for the electrodeposited film surface is due to the oxidation in the air. The electrodeposited Si film was also characterized by reflectance and photoluminescence (PL) measurements. These measurements demonstrated that the electrodeposited film contains amorphous Si with the band gap of about 1.55 eV and a broad PL peak centered at the photon energy of 1.37 eV.

Effects of electrode potential and SiCl4 concentration on electrodeposition of Si were examined in trimethyl-n- hexylammonium bis(trifluoromethylsulfonyl)imide (TMHATFSI) containing various concentrations of SiCl4. A rougher and thicker film was electrodeposited in TMHATFSI containing higher concentration of SiCl4 or at more negative electrode potential. Current efficiency estimated from EDX spectra is highest at [?]2.0 V vs. Pt quasi-reference electrode (Q.R.E.). Time evolution of Si electrodeposition at [?]2.0 V vs. Pt Q.R.E. was also studied in TMHATFSI containing 0.1 M SiCl4. As the electrolysis progressed, the thickness of electrodeposited Si film increased, while current efficiency decreased, with approaching constant values.

Elimination of boron species viasolvent extraction with 2,2,4-trimethyl-1,3-pentandiaol was engaged in a flow-type device into which the aqueous solution dissolving diatomaceous earth, a candidate of the resource for high-purity silicon material. The flow-type device has a 2-stage channel with 1.0 mm width, 0.10 mm depth, and 25 mm length each, and the specific interfacial area is comparable to a typical microchannel device. Residual boron content in the aqueous solution decreased to less than 0.1 ppm after the solvent extraction under the restriction of short contact duration shorter than 100 ms. In addition, the analysis with density functional theory indicated that the number of neighbor carbon on the central carbon is one of the keys for improvement of reactivity of extractant. Hence, it is suggested that the flow-type microchannel device with solvent extraction with alkyldiol extractant can be utilized as an attractive approach toward the production of high-purity silica as a source for solar-grade silicon.

The present simplified electrochemical model of a horizontal upward-facing Zn anode combined with a Ni(OH)2/NiOOH cathode thus reasonably simulates the time-dependent coupling phenomena between the electrode surface morphological variations and the ionic mass transfer rate inside the model-pore mesoporous microstructure that extends across the width of a Zn battery cell.

The diffusion coefficient of SiCl4in trimethyl-n-hexylammonium bis(trifluoromethylsulfonyl)imide was estimated by means of an optical moiré-pattern technique. It revealed that the diffusion coefficient varies with concentration from 0.79 × 10−6cm2s−1at 0.1 mol L−1to 1.05 × 10−6cm2s−1at 0.4 mol L−1at 298 K. This technique is superior to any other methods to measure the diffusion coefficient especially in the following point. The conventional electrochemical methods such as chronopotentiometry and chronoamperometry yield just a single effective diffusivity over the similar concentration range. On the other hand, the moiré-pattern method is so powerful that just one experiment is adequate to estimate the concentration-dependent diffusivity because the local diffusivities at the points with different concentrations can be measured at once.