The electrodeposition process of Li metal in 1.0M LiTFSI–ionic liquid (N-methoxymethyl-N-methylpyrrolidinium) bis(trifluoromethane-sulfonyl) imide was observed in situ by optical microscope. ...Morphological variations of electrodeposited Li dendrite and its growth rate were examined and the ionic mass transfer rate in the vicinity of the electrode surface was discussed. Once the dendrite starts to grow, its length is proportional to the square root of time. This indicates that the Li+ mass transfer rate affects its growth. Dendrite growth process can be classified into two regions depending on its growth rate: the initiation period and the growing period with swinging behavior probably caused by residual stress.
Li electrodeposition on liquid Ga substrates was carried out in PC-LiClO4 at 40 °C. It was found that interfacial flow phenomena were induced by differences in interfacial tension between the liquid ...Ga and the liquid Ga-Li alloy formed on the substrate under potentiostatic electrolysis at −1.0 V (vs. Li+/Li), which caused the interfacial shape change of the liquid Ga electrode. We carried out in-situ observations in order to understand why such interfacial phenomena occur between the liquid electrolyte and the liquid metal cathode. Moreover, a significant difference in electrochemical response between liquid and solid Ga substrates was also noticed employing the current-time transient technique. These experimental results suggest that the process of liquid Ga-Li phase formation by the dissolution of electrodeposited Li atoms into the liquid Ga substrate dominated during the initial stage of Li electrodeposition. In contrast, the typical peaks induced by growth of solid Ga-Li alloy phase and Li metal phase were observed on solid Ga substrates. These results provide new insight into the design of electrochemical processing involving liquid electrolyte/liquid metal interface.
•Li electrodeposition on both liquid and solid Ga cathodes in propylene carbonate containing LiClO4 was carried out.•Interfacial flow phenomena induced by differences in interfacial tension between Ga(l) and Ga-Li(l) alloy were observed.•The electrochemical response is related to the formation of the liquid Ga-Li alloy phase on the liquid Ga cathodes.•Future work should take into account macroscopic hydrodynamics induced by electrochemical reactions on liquid metal cathodes.
The electrodeposition of silicon from silicon tetrachloride in the hydrophobic room temperature ionic liquid trimethyl-n-hexyl ammonium bis-(trifluoromethylsulfonyl) imide was investigated by cyclic ...voltammetry and chronoamperometry. In situ electrochemical quartz crystal microbalance (EQCM) impedance spectroscopy was used to estimate the mass of films during deposition. The charge efficiency estimated from EQCM measurements is ∼190–250% for four-electron silicon reduction. However, compositional analysis by XPS shows that the EQCM current efficiency estimates are artificially high due to ionic liquid inclusion in the films. Taking the mass concentration of impurities into account, the best-case estimate of current efficiency is found to be approximately 130% for constant potential deposition, suggesting silicon may not have been completely reduced at the potentials investigated, or a chemical reaction step occurs. We also consider that the EQCM analysis may include too many deviations from assumptions for accurate estimation of mass with the conditions studied.
This paper describes the initial stages of electrochemical growth of Cu and Ni nanowires in polycarbonate (PC) track-etched membranes as the template. The diameters of the wires ranged from 50 to 200
...nm. A thin Pt–Pd layer (∼30
nm thick) was sputter-deposited onto one side of the membrane and used as the cathode. The layer was not thick enough to seal the pore mouths. Cathodic current in the early stages of both Cu and Ni electrodeposition abruptly decreased after a period proportional to the pore diameter. Growing Cu grains plugged the pore openings causing the current to decrease, while the Ni deposition initially yielded a hollow tube in each pore resulting in a nanostructure transition of the tube to the wire at the growth front and a decrease in the current.
Magnetic nanoparticles of FePt intermetallic compound were formed in molten LiCl–KCl–CsCl electrolyte under 1
atm of Ar atmosphere by plasma-induced cathodic discharge electrolysis. By utilizing the ...displacement reaction between the Fe(0) and Pt(II), FePt intermetallic compound nanoparticles were obtained from the melt. The displacement reaction produced small primary particles that considerably aggregated to form larger secondary particles. The coercivity of the obtained FePt intermetallic compound nanoparticle increased with a longer residence time in the melt. The coercivity of the FePt intermetallic compound nanoparticle obtained after a residence time of 3
h was measured to be 199
mA
m
−1. FePt intermetallic compound nanoparticles could also be obtained by the co-depositing Fe and Pt from Fe(II) and Pt(II) in the melt. In this case, the primary particle size distribution became broader, but the aggregation of primary particles was suppressed. The coercivity of the obtained FePt intermetallic compound nanoparticles showed a quite high value of 245
mA
m
−1 that did not depend on the residence time.
A transient natural convection develops along vertical plane Cu electrodes during the galvanostatic electrolysis. The time variations of both the concentration profile of CuSO
4 and the velocity ...profile of a 0.6
M CuSO
4 aqueous electrolyte were measured. The mass transfer rate of Cu
2+ ion as well as the natural convective fluid motion was analyzed. The effect of electrode spacing on the transient natural convection was focused. The overshooting phenomenon caused by the transient diffusive and convective mass transfer rate was observed. Numerical simulation may provide as better understanding of the phenomena.
Water electrolysis was conducted in both alkaline (25
wt.% KOH, 2
wt.% KOH) and acid (0.1N H
2SO
4) solutions for 8
s under microgravity environment realized in a drop shaft. The gas bubble formation ...of hydrogen and oxygen on platinum electrodes was observed by CCD camera. In alkaline solutions, a bubble froth layer grew on the electrode surface. Hydrogen bubble size was smaller than that of oxygen. The current density at constant potential decreased continually with time. In spite of the growth of a bubble froth layer on the electrode, the electrolysis never stopped, apparently because fresh electrolyte is supplied to the electrode surface by microconvection induced by the gas bubble evolution. In acid solution, hydrogen gas bubbles frequently coalesced on the cathode surface, yielding a larger average bubble than that of oxygen. The current density did not vary at constant potentials from –0.4 to −0.8
V versus reversible hydrogen electrode (RHE), because the effective electrode surface area was significantly reduced by the larger bubble size compared to alkaline electrolyte. The present experiments indicate that, especially in a microgravity environment, the bubble evolution behavior and the resultant current–potential curves are significantly influenced by the wettability of the electrode in contact with the electrolyte.
Cu nanowire arrays were electrodeposited with a template of a polycarbonate (PC) filter. Pt–Pd alloy film was sputtered on one side of the PC filter and then used as cathode in 0.6 M CuSO
4 aqueous ...solution (pH 2). Potentiostatic electrodeposition at −400 mV vs. Cu reference electrode was conducted in two kinds of electrolytic cell configurations, cathode over anode (C/A) and anode over cathode (A/C). The transient variation of the cathodic current clearly showed four stages in both cell configurations; (I) nucleation and crystal growth mode of Cu on the Pt–Pd film, (II) filling up with electrodeposited Cu in the nanosized pores, (III) covering of the surface of the template with Cu, and (IV) growth of a Cu thick film. In Stage II, the cathodic current increased in the A/C configuration, while it decreased in the C/A. The duration time of Stage II was shorter in the A/C configuration than that in the C/A. The difference of the cathodic current variation between the two configurations was smaller with smaller sized pores. These phenomena suggest that the ionic mass transfer rate of Cu
2+ ion accompanied by electrodeposition is enhanced by a kind of natural convection even in and around such a nanosized pore and that the pores are filled up faster with electrodeposited Cu in the A/C than in the C/A configuration.
Iron thin films were electrodeposited on a copper substrate in FeSO
4 aqueous solution under a magnetic field (0–5
T) at 298
K. The surface morphology was observed by the atomic force microscopy ...(AFM). It was drastically changed from an angular to a wavy shape by superimposing the magnetic field. Moreover, rectangular shaped precipitates were aligned along the magnetic field. The grain size decreased with increasing in magnetic field intensity,
B. The AFM image was characterized by the anomalous scaling method in order to quantitatively analyze the magnetic field effect on surface roughness. The roughness exponent,
α, and the growth exponent,
β, decreased as
B increased. The variation of scaling parameters with
B may be utilized to improve the surface morphology evolution and the transition of the crystal growth induced by the magnetohydrodynamic convection can be phenomenologically discussed.
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