H.T. Yuan

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.

Electrochemical characteristics of Mg2−xAlxNi (0≤x≤0.5) alloys

Abstract The Mg-based hydrogen storage alloy Mg 2− x Al x Ni (0≤ x ≤0.5) have been successfully synthesized by a diffusion method (DM). The structures of these alloys have been examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical characteristics have also been investigated, such as corrosion resistance and electrochemical capacity. It is found that a new phase appears when Al is added to the Mg–Ni system. It can be observed that there are a large number of defects on the alloy surface, which strongly affect its characteristics. The electrochemical capacity and cycle lives of Al-containing alloys increase strongly compared to the Al-free alloy. With increasing Al concentration in the alloys, the capacity also increases due to the increase of the amount of the new phase.

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.

Effect of Zn on the hydrogen storage characteristics of multi-component AB5-type alloys

The mischmetal-based hydrogen storage alloy systems MlNi3.8Co0.5Mn0.4Al0.3Znx (Ml, La-rich mischmetal; 0<x<0.2) have been successfully synthesized by the diffusion method (DM). The characteristics of these alloys have been carefully investigated by means of XRD, PAT, PCT, EIS and measurement of electrochemical capacity. Experimental results show that the unit cell volume becomes larger and the point defect density increases strongly due to the diffusion of Zn. The presence of Zn decreases the desorption plateau and prevents losing the capacity to a certain degree at high discharge current density. Electrochemical impedance spectra (EIS) results show that the rate-determining step is the charge-transfer reaction on the alloy/electrolyte interface. The charge-transfer resistance of the electrode increases with increasing Zn concentration due to the formation of an oxide layer and the reduction of active sites on the electrode surface. So the concentration of Zn in the alloy should be limited to below x=0.1. The Zn-free multicomponent AB5 alloy has also been examined for comparison.

Characteristics of Mg2−xTixNi1−yCuy–H2 (0<x<2, 0<y<1) alloys

Abstract The Mg 2− x Ti x Ni 1− y Cu y (0 x y 2 system with and without the treatment of F-solution. A study of the hydrogen desorption process was also carried out. The results show that the main phase of the alloys is an Mg 2 Ni structure. The gas–solid phase reaction can occur without detailed surface treatment and activation. A study on the anti-corrosion properties in alkaline solution of Mg 2− x Ti x Ni 1− y Cu y (0 x y

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.

Storage of hydrogen–methane mixture in the complex sorbent of activated carbon–TiMn1.5 alloy

Abstract The possibility of storing the mixture of H2 and CH4 in a complex sorbent composed of superactivated carbon and TiMn1.5 alloy was experimentally studied. The storage capacity of the complex sorbent was shown nearly equal to the sum of the storage capacity of the component sorbents. Therefore, sorptive storage is technically feasible for a clean fuel mixed with natural gas and hydrogen. As a consequence, the storage pressure is considerably decreased comparing to that of compression technology.

Characteristics of mixed hydrogen storage electrode

Abstract Mixed hydrogen storage electrodes were made of hydrogen storage alloy powder M L Ni 3.75 Co 0.55 Mn 0.42 Al 0.27 (M L denotes La-rich mischmetal) mixed with powder of other components. The changes of the electrochemical characteristics of hydrogen storage electrodes were investigated. In this paper, we studied mixed hydrogen storage electrodes modified by various types of metal powders. The results showed that the electrochemical characteristics of hydrogen storage electrodes modified by metal powders such as Co, Ni, Mo and W were improved.