Zhang Hengbin

Preparation and properties of the aluminum-substituted α-Ni(OH)2

Abstract The aluminum-substituted α-Ni(OH) 2 was prepared by direct titration method in a buffer solution. The structure was analyzed by XRD, IR and TG. Its electrochemical properties as a positive electrode in Ni-metal hydride cell were examined by the charge–discharge experiments. The results indicate that the electrode performances of the aluminum-substituted α-Ni(OH) 2 are superior to general β-Ni(OH) 2 , especially, the specific capacity of discharge, the specific energy of discharge and the cycle life have been enhanced obviously.

Synthetic studies of nanocrystalline composite oxides with the perovskite structure based on LaFeO3

Abstract The precursors for synthesis of nanocrystalline composite oxides La1−xSrxFe1−yCoyO3 (x = 0.2, 0.4; y = 0.5, 0.6) were prepared using the polyethylene glycol and citrate methods. After the solid-phase reaction at 550°C for 2 h, the mean diameters of the nanocrystalline grains were about 15 nm. The results indicate that the effects of the solid-phase reaction depend on the distribution of various components in the precursor and the conditions of preparing them. The polyethylene glycol method is superior in many respects to the citrate method.

EPR spectra of nanocrystalline composite oxide LaFeO3 with the perovskite structure

Abstract Nanocrystals of LaFeO3 with mean grain diameters of 12.4, 12.6, 14.4, 16.0 and 16.3 nm were compacted into pellets under static pressure of 0.5, 1.0 and 1.5 GPa in the axial direction at room temperature. Their EPR spectra change with grain sizes and compacted pressures. The results show that the g values increase a little with the increment of compacted pressures, whereas the peak intensities of EPR spectra of nanocrystalline materials are about 103 times as strong as those of conventional materials. This paper discusses characteristics of EPR spectra of nanocrystalline composite oxide LaFeO3.

The effect of lanthanide as counter ions on the oxidation activity of molybdovanadophosphoric acid

Abstract In this paper, we suggest a method of preparing pure molybdovanadophosphoric acid and of effectively checking its purity. Substituting lanthanum for H+ ion in molybdovanadophosphoric acid does not affect the oxidative dehydrogenation reaction. Because the process of dehydrogenation is related with the rapid diffusion of protons and electrons, it is proposed that the addition of lanthanum has no effect on the diffusion process. However, lanthanum noticeably affects the oxygen addition reaction. It was considered that surface polyanions play a main role in the oxygen addition reaction due to the slow diffusion of bulk oxygen to the surface. Thus it may be reasonable that lanthanum does not decrease the oxygen-donating ability of polyanions, or retards the diffusion of bulk oxygen to the surface. We conclude that water molecules surrounding polyanions in catalysts at high temperatures might retard the diffusion of bulk oxygen to the surface, which would result in a decrease in the rate of the oxygen addition reaction.

Preparation of nanocrystalline composite oxide SrRuO3 and its application in the fuel cell as negative electrode materials

Abstract Nanocrystalline composite oxide SrRuO3 was synthesized by the reverse drop coprecipitation method. Pure SrRuO3 and SrRuO3 adsorbed on active carbon powder were used as negative electrode material in the fuel cell, the cell performances were examined by cyclic voltammetry. The experiments indicated that the new electrodes are better electrocatalysts for methanol oxidation. Moreover, the structure and morphology of nanocrystalline SrRuO3 were characterized by XRD and TEM.

Electrochemical investigation of adjacent tri-substituted vanadotungstophosphate with keggin structure

The redox properties of K6PW9V3O40 - a tungstophosphate substituted by three vanadium atoms at the 1, 2, 3-positions with Keggin structure are described. The oxidizability of this compound is much higher than that of the unsubstituted tungstophosphate. The three vanadium atoms in K6PW9O40) can be reduced step-by-step and have better redox reversibility. The influence of the pH, ionic strength and solvent on the redox properties of this compound are also reported.