Some biomimetic reactions observed with the aid of aqueous/organic, W/O, two phases or liquid membrane, LM, systems were introduced. The reactions introduced were mostly those reported by the group of present authors as follows; (1) Transformations of porphyrin iron(III) complex, Fe(P), and α-tocopherol, α-TOH, derivatives in O contacted with W. (2) The oxidation of Fe(P) in O with an oxidant in W, α-TOH in O with nitric oxide in W or hydroquinone in O with oxygen in W, and the reduction of quinone in O with β-nicotinamide adenine dinucleotide in W. (3) A respiration mimetic reaction accompanied by the selective ion transfer at the W/O interface. (4) Biomimetic charge transport reactions observed by LM systems such as the oscillation of membrane current. (5) A new type of membrane transport reaction realized in the presence of an applied electrical potential gradient parallel to the W/membrane interface. The processes of above-described reactions were elucidated based on the voltammetric methods and concepts taking into account the properties common to both artificial LMs and biomembranes. A method proposed by present authors for the elucidation of the membrane transport process was also introduced.
Heat treated SiO in the temperature range of 400 to 1000°C were characterized using XRD and TEM, and their battery performance as an anode material for lithium ion batteries were evaluated in half-cells. A SiO anode using polyimide as binder showed high discharge capacity of 1500 mAh g−1 at the 2nd cycle and excellent cyclability with a capacity retention of 97.8% at the 100th cycle. A lithium ion battery consisting of a LiFePO4 cathode and a SiO anode showed excellent cycle-life (over 600 cycles), high-rate capability, and thermostability in wide temperature range of −30 to 120°C.
Thickness change of large capacity SiO anode was evaluated through in-situ measurement of a laminate type cell during charge and discharge. The change of a counter electrode thickness was eliminated from the measurement of cell thickness, because the counter electrode was accommodated in a space in a hard separator. At first charge SiO anode gained its thickness by 38.9%. Volume changes of each component of anode such as active material, conductive additive, binder and pore were evaluated. It was found that with large volume change of SiO there was also a large pore volume change in the SiO anode.
Rapid electron transfer phenomena were observed in two redox reactions involving molecular DNA. One such reaction was that of non-intercalative iron(III) meso-tetrakis(N-methylpyridinium-4-yl)porphyrin chloride (Fe(III)(4-TMPyP)Cl) in DNA solution. The reaction was largely inhibited in pure DNA solution, but not when the DNA had been intercalated with H2, Ni(II), Pd(II)(4-TMPyP) or ethidium bromide. The other redox reaction was that of methylene blue (MB+) on a DNA film cross-linked with ZrOCl2·8H2O. Using an electrochemical quartz crystal microbalance (EQCM), the MB+ that had been pre-adsorbed onto the DNA film was hypothesized to have been dimerized via a two-electron reduction and could subsequently be reoxidized back to its original state. These results suggest a fast electron transfer across the DNA strands.
An asymmetric combination of alkali-treated soft carbon (ASC) with activated carbon fiber (ACF) electrodes has been utilized to develop a novel electric double-layer capacitor (EDLC). The capacitance of ASC electrode was significantly increased after electrochemical activation at the first high potential cycling. Electrochemical measurements were carried out by charge-discharge polarization and ac impedance methods using a 3-electrode cell with propylene carbonate (PC) dissolving 1.0 M tetrafluorobrate (BF4−) salt of tetraethylammonium (TEA+) or lithium (Li+). The charge-discharge performance of the cell that consists of ASC as the negative and ACF as the positive electrodes with TEABF4 electrolyte, denoted as ASC(−)/TEABF4(PC)/ACF(+), showed higher specific capacitance than other systems for the cycling in the voltage range of 0.0–3.0 V. The cell using LiBF4 electrolyte, ASC(−)/LiBF4(PC)/ACF(+), gave poor capacitance behavior probably due to undesirable electrolyte decomposition at the positive electrode. The ACF(−)/ASC(+) cell using TEABF4/PC also showed high capacitance, high coulombic efficiency and good cycle stability. The optimized cell with TEABF4/PC electrolyte had over 100 Wh kg−1 of energy density for the cycling in 0.0–3.5 V range.
Vanadium pentoxide xerogel was prepared by irradiation with microwaves and successfully applied as the active cathode material of a magnesium rechargeable battery. The structure and electrochemical properties of the V2O5 xerogel were investigated and compared with V2O5 prepared by conventional heat-treatment. X-ray diffraction revealed that the V2O5 xerogel prepared by MW irradiation has low crystalline structure. Charge-discharge tests revealed a specific capacity of 463 mAh g−1, which was much larger than of V2O5 prepared by conventional heat-treatment (190 mAh g−1).