Glucose sensing with use of glucose oxidase, p-acetamidophenol, and Nafion-coated Glassy carbon electrode has been attempted aiming quantitative analysis of glucose without interference of electrochemically active species such as ascorbic acid, uric acid, and p-acetamidophenol. Electrochemical measurements of the three interfering species at a Nafion-coated glassy-carbon electrode have revealed that the electrode can oxidize only p-acetamidophenol. It has been also found that p-acetamidophenol works well as an electron mediator for glucose oxidase. Combination of those facts led to fabrication of a glucose sensor that avoids any interference by ascorbic acid and uric acid. When concentration higher than 5.0 mM is chosen for p-acetamidophenol as the electron mediator, further addition of p-acetamidophenol gives no significant changes in the oxidation currents. In addition, even oxygen dissolved in solution does not influence magnitude of sensing currents. Therefore, the glucose sensor prepared in this study is not disturbed by all electrochemically active substances which usually give the most serious interferences for oxidative glucose sensing.
A numerical analysis model for a porous electrode that works in the Tafel region has been developed in order to understand the alternative current impedance behavior. The reaction is uniform in thickness in the lower current density region. However, the reaction takes place more at the electrolyte side in the higher current density region. The increase of the localization of the reaction would result in the increase of the overpotential and the deformation of the arc of the real part—the imaginary part (Nyquist) plot. Therefore, the alternative current impedance analysis should be applied to determine the ionic resistance in the porous electrode from the electronic resistance and the other kinetic parameters of an electrode reaction.
We investigated the relationship between the electrode performance, crystal structure and electronic structure of LiMn1−xMxO2 (M=Mn, Co, Ni, Zn). The discharge capacity of o-LiMn1−xMxO2 decreased compared to that of LiMnO2. On the other hand, the cycle fading decreased since the maximum capacity was improved by substitution with Co or Ni. The crystal structure analysis by neutron powder diffraction was examined for LiMn1−yMyO2 (M=Co, Ni). The bond angle variances increased due to the Co or Ni substitution. The electron density distribution was obtained by XRD using the MEM/Rietveld method. The electron density distribution shows that the covalent bonding of (Mn,M)–O of LiMn1−xMxO2 is stronger than that of o-LiMnO2. Next, we calculated the net charge of each atom, the bond overlap population of Li–O, Mn–O, M–O, the density of states, and the electron density of o-LiMn1−xMxO2 using first principles calculation by the DV-Xα method and FLAPW method. Based on the results, the Li ionicity always remained high and the covalent bonding of Mn–O and M–O of each o-LiMn1−xMxO2 is stronger than that of o-LiMnO2. As a result, the covalent binding of (Mn,M)–O is important for good cycle performance.
Relative differences between internal cation mobilities in molten (Li, K) F have been measured by countercurrent electromigration (Klemm method) at 1023 K. Internal mobilities of K+ are larger than those of Li+ in all composition on which we have measured so far. More striking feature is that the isotherms have minimum of mobilities at ca.xK=0.5. The local structural parameters would be highly related to the ionic conduction behavior in molten fluorides.
Zinc negative electrode has high energy density and less expensive materials for battery in general. However, it generates dendrite when it charged as electrode for secondary battery, therefore, the use for secondary battery is difficult. At this opportunity we would make secondary battery using zinc with aqueous electrolyte. We discovered the dendrite is controlled by glycerin and saccharin in ZnSO4 solution. Lithium manganate is one of opposite electrodes that performed in this condition. In this study, we made aqueous lithium ion-zinc secondary battery with those electrodes and electrolyte, and evaluated then optimized that performance. This battery has approximately 100% charge-discharge efficiency. Their charge and discharge cycle performance depends on concentration of ZnSO4 and mass of LiMn2O4. The density of most suitable ZnSO4 for LiMn2O4 of each mass may be existing. Relatively higher percentage of LiMn2O4 mix has better performance. This battery performed more than 400 charge and discharge cycles as maximum and 70 mAh·g−1 as maximum of discharge capacity was provided. Furthermore, we can expect future improvement of performance as a secondary battery by optimizing these conditions.