D. Y. Song

Electrochemical Performance of Anatase Nanotubes Converted from Protonated Titanate Hydrate Nanotubes

Titanium oxides with one-dimensional nanostructure are of significant interest for the electrochemical lithium insertion and extraction because of their large specific surface area and numerous surface defects. Nanotubes with 10-15 nm outer diameters and 200 ∼ 400 nm long were prepared by a reaction between rutile and caustic soda under hydrothermal conditions. These nanotubes are protonated titanate and can be converted into the anatase nanotubes after calcination at 500°C in argon atmosphere. The anatase nanotubes exhibited a high reversible discharge capacity, excellent high-rate discharge capability, and good cycle stability under the large current density.

Impedance studies of nickel hydroxide microencapsulated by cobalt

Abstract Nickel hydroxide is used as an active material in pasted-type nickel hydroxide electrodes for rechargeable alkaline batteries. The electrochemical impedance spectroscopes of different nickel hydroxide electrodes were measured. The results were analyzed using a standard equivalent circuit model including a Warburg impedance term. The Nyquist plots were used to interpret the characteristics of the different electrodes. The nickel hydroxide electrode deposited by cobalt has shown lower charge transfer resistance and higher electronic and protonic conductivity.

Synthesis of carbon nanotubes by catalytic decomposition of methane using LaNi5 hydrogen storage alloy as a catalyst

Abstract Carbon nanotubes were synthesized by catalytic decomposition of methane using a hydrogen storage alloy of LaNi 5 with a CaCu 5 type of hexagonal structure as a catalyst. It was found that surface treatment of LaNi 5 alloy particle in KOH solution was effective for providing catalytic sites for carbon nanotube growth. The reaction gas of methane could easily penetrate and reach the catalytic sites on metallic nickel through the decomposed loose surface layer of La 2 O 3 . The metallic nickel on the surface layer of LaNi 5 alloy particle was dominant for growth of carbon nanotubes. The composite of carbon nanotubes with hydrogen storage alloy would be expected to have a potential application in the field of hydrogen energy.

Rotor-like ZnO by epitaxial growth under hydrothermal conditions

Rotor-like ZnO was grown from a mixture of rod-like ZnO powder and a saturated Zn(OH)(4)(2-) solution under moderate hydrothermal conditions at 100 degree C, in which the precursor rod-like ZnO crystal plane acts as a matrix core, and the branched nanorods showed fast epitaxial growth on the six directions around the prism core.

The electrochemical properties of MmNi3.6Co0.7Al0.3Mn0.4 alloy modified with carbon nanomaterials by ball milling

Abstract The MmNi3.6Co0.7Al0.3Mn0.4 alloy surface is modified with multiwalled carbon nanotubes and carbon black (10 wt.%) by ball milling for 50 min. The microstructures of the obtained materials are examined and analyzed by X-ray diffraction, SEM and TEM. It is confirmed that the surface of AB5 alloy is modified by shorter carbon nanotubes and thin carbon flake, respectively, when carbon nanotubes and carbon black are added. The electrochemical properties of the obtained materials are measured and compared with those of the original AB5 alloy. It is found that high rate discharge ability of the alloys after surface modification by carbon nanomaterials increases to some extent due to the decrease of electrochemical reaction resistance and the increase of double capacitance as obtained by electrochemical impedance spectra. In particular, the modified alloy with the carbon nanotubes shows a superior performance to carbon black, especially in the discharge rate of 2000 mA/g. Besides, the addition of carbon nanomaterials reduces the extent of the amorphism of the AB5 alloy during ball milling.

Electrochemical Hydrogen Storage of Nanocrystalline La2Mg17 Alloy Ballmilled with Ni Powders

La 2 Mg 1 7 -based nanocrystalline alloys were prepared by ballmilling La 2 Mg 1 7 alloy with Ni powders. Electrochemical charging and discharging of the ballmilled La 2 Mg 1 7 -based nanocrystalline alloy succeeded due to theformation of highly dispersed metallic Ni particles through the nanocrystalline alloy matrix. The first discharge capacity of the La 2 Mg 1 7 alloys ballmilled with Ni powders in a weight ratio of 1:2 was near 990 mAh/g, corresponding to a hydrogen storage capacity of 3.69 wt %. Inlaid metallic Ni at the surface layer of the nanocrystalline alloy matrix served as electrocatalytic reaction sites and hydrogen adsorption sites to accelerate the electrochemical charging and discharging process.

Electrochemical Hydrogen Discharge Properties of MgNi-Carbon Nanotube Composites

MgNi-carbon nanotube composites were prepared by ballmilling the MgNi alloy and multiwalled carbon nanotubes (CNTs, 10 wt %) at various periods of time. It was confirmed by scanning electron microscope images that the MgNi alloy surface wets modified by shorter and broken CNTs. The MgNi-CNT composites prepared by ballmilling after 60 min were found to show mproved electrochemical properties with respect to the original MgNi alloy. In particular, the discharge capacity of the composite electrode increased from 400 to 480 mAh/g by surface modification with CNTs. The electrochemical reaction activity of the composite electrode was improved as confirmed by cyclic voltammogram. The analysis of the electrochemical impedance spectra showed that the double layer capacitance of the composite electrode increased under steady-state condition, which related to surface area of the particles. On the contrary, however, the improvement of the electrode cycle life was unsatisfactory, which probably attributed to the further generation of a new MgNi-CNT interface.

The chemical preparation of Mo(W)Co(Ni) and their influence on hydrogen storage electrode

Alloys with cooperative effects such as MoCo3 and WCo3 attract researchers because of their high electrocatalytic property. These alloys prepared by melting are very difficult to pulverize, and it is considerably difficult to prepare them as second phase in a hydrogen storage alloy. The alloy powders of MoCo3, WCo3 and MoNi3 with large surface area were prepared by solid state chemistry in this paper, then mixed with a hydrogen storage alloy. The mixed hydrogen storage alloy electrodes were measured with electrochemical methods. The results showed that the mixed hydrogen storage alloy electrode had advantages such as higher activation rate, higher discharge capacity and better high rate discharge characteristics.

The characteristics of mixed hydrogen storage electrode with Bi2(MoO4)3

Abstract Bi 2 (MoO 4 ) 3 could be used to catalyze the oxidation–reduction reaction related to hydrogen, so we tried to use Bi 2 (MoO 4 ) 3 and P 2 O 5 –MoO 3 –Bi 2 O 3 –SiO 2 as catalyst to catalyze the reaction of absorption and desorption of hydrogen storage electrodes. In this paper, Bi 2 (MoO 4 ) 3 and P 2 O 5 –MoO 3 –Bi 2 O 3 –SiO 2 were prepared in order to improve the electrochemical activity of the hydrogen storage alloy electrodes. The results showed that the electrochemical capacity and high rate discharge characteristics were improved.

Structure and electrochemical properties of Zr(V0.2Mn0.2Ni0.6 − xCox)2.4 hydrogen storage alloys

Abstract The structure and hydrogen absorbed properties of a series of the multicomponent Zr(V 0.2 Mn 0.2 Ni 0.6 − x Co x ) 2.4 alloys have been investigated as a negative electrode in the metal hydride batteries. The crystal structure turned out to change as a function of substituted cobalt from a cubic C15 type structure to a hexagonal C14 type structure. There were anomalies in the relation among the hydrogen plateau pressure from PCT, electronic factor of the alloy and A 2 B 2 tetrahedral interstice for hydrogen occupation. The Zr(V 0.2 Mn 0.2 Ni 0.5 Co 0.1 ) 2.4 electrode was used to evaluate the electrochemical characteristics including activation, cycle life, electrocatalytic activity and hydrogen adsorption. It was found that both the hydrogen adsorption process and hydrogen diffusion process took place in the electrochemical impedance spectra of the electrode used here.