The ultra-low platinum loading electrode (ULPLE) with new concept that fine Pt particles are loaded mainly at electrochemically active site located on the surface of carbon in contact with cluster of polymer electrolyte, has been experimentally verified to be able to minimize the Pt loading level down to 0.012 mg cm-2 with its high utilization of approx. 2.5 times higher than that of Pt supported carbon. This novel electrode was realized by special process based on ion-exchange reaction between Pt complex cation and proton of the counter ion of polymer electrolyte on carbon powders followed by reduction of its cation under hydrogen atmosphere at lower temperature of 180℃. The ULPLE will be expected to show little deterioration phenomenon losing the active surface area of Pt particles during its operation time.
The reduction of chlorodimethylphenylsilane was carried out in the presence of anodically dissolved magnesium ion. After 1.0 F/mol of electricity was passed based on the chlorosilane (pre-electrolysis), the chlorosilane was added to the resulting electrolyte, and the solution was just stirred over night to give the corresponding disilane in 13% yield. Moreover, the electroreduction of the chlorosilane using platinum electrodes was carried out in the presence of the anodically dissolved magnesium ion, and the disilane was found to be obtained in 20% yield, while the disilane was not obtained by electroreduction using Pt electrodes without pre-electrolysis. The flow-system equipped with carbon electrodes was applied to the electroreduction of chlorodimethylphenylsilane in the presence of the anodically dissolved magnesium ion to give the disilane in 97% current yield. The electroreductive polymerization of dichloromethylphenylsilane was also carried out by using the flow-system and the pre-electrolysis technique to give the corresponding polymer in 17-24% yield. The number averagemolecular weights of the resulting polysilanes determined by GPC were 10900-17500. The active reductant in the present electroreduction system is probably electrogenerated during the electrolysis using magnesium electrodes, and it is able to promote the reductive synthesis of polysilanes.
Structural effects on the rate of the dechlorination of chlorobenzene have been studied using the low index planes of platinum and silver in acetonitrile solution. Chlorobenzene is electrolyzed on platinum electrodes using naphthalene as a mediator at -2.94 V vs. Ag/Ag+. The main product is benzene. A reaction via a mediator does not depend on electrodes in general, because it is a homogeneous catalytic reaction. Surface structure, however, affects the partial current density of benzene (jC6H6) on platinum electrodes: Pt(111)<Pt(110)∼Pt(100). On silver electrodes, jC6H6 shows no structural effect in the electrolysis using naphthalene. Electrolysis without naphthalene gives the same structural effect as that with naphthalene on platinum electrodes, whereas no silver electrode reduces chlorobenzene at -2.94 V vs. Ag/Ag+ without naphthalene. Therefore, the anomalous structural effect on the electrolysis with naphthalene is attributed to the existence of a direct reduction of chlorobenzene on platinum electrodes. Silver electrodes reduce chlorobenzene to benzene at more negative potential -3.17 V vs. Ag/Ag+ without naphthalene. The value of jC6H6 depends on the surface structure: Ag(110)∼Ag(111)<Ag(100). The flat (100) terrace has the highest activity for the dechlorination of chlorobenzene.
Coating with polyallylamine (PAA) over artificial graphite was applied to reduce its irreversible capacity. The coated graphite showed the same flat charge/discharge curves as the non-coated one. The irreversible capacity was reduced from 67 to 22 mAh/g in EC-based electrolyte by a small amount coating of PAA without change in the discharge capacity. PAA was found effective even in PC-based electrolyte. SEM observation showed the thin layer of PAA, which prevented the direct contact of electrolyte on the graphite surface. The charge characteristic, however, was deteriorated, which might be due to the increased resistance of inter-particle and/or of Li-ion diffusion through the PAA layer.
The purpose of this investigation was to study electroless Au plating by displacement reaction from citric acid bath (106 mM (NH4)3C6H5O7 + 14 mM C10H14N2Na2O8 2H2O + 5 mM KAu(CN)2) containing sodium dodecyl sulfate (SDS) or polyethylene glycol (PEG) by means of electrochemical method, scanning electron microscopic observation, measurement of adhesive strength between Au and Ni films, etc. SDS accelerated the oxidation reaction of Ni and the degree of corrosion for Ni film during Ni/Au displacement reaction was large in the presence of SDS. On the other hand, PEG inhibited the oxidation reaction of Ni and the degree of corrosion was small in the presence of PEG. Electroless Au film which has a strong wire pull strength and adhesive strength was obtained from a bath containing PEG by displacement reaction.