No abstract

The influence of C1-ion concentration on the active dissolution and passivation of polycrystalline nickel rotating disk electrodes in sulfuric acid-potassium sulfate solutions at pH 2.6 and 25~ was studied. The voltammetric data suggest that the passive layer results from a complex reaction involving the electrodissolution of the base metal, the formation of the anodic layer and its partial chemical dissolution. The influence of C1-ions under different hydrodynamic conditions is discussed taking into account the competitive adsorption involving C1-ions and species containing oxygen at the initial stages of the reaction yielding soluble products, and the appearance of Ni(OH)2 as a new phase. Solution stirring favors the electrodissolution reaction by increasing the transport rate of C1-and H § ions to the electrode surface, and simultaneously decreasing the thickness of the Ni(OH)2 layer.

SOLID POLYMER ELECTROLYTE 1729-3~ 19 ~ and 24 ~ for X above 0.8, while no peaks were observed for X below 0.6. Since the positions of these two peaks were in complete agreement with those of PEa, the ethylene oxide (EO) chain of PEM is considered to crystallize. It is likely that the mobility of the EO chain is large enough to crystallize in this composition range due to the small cross-linking density, which decreases with increasing X. A marked decrease in the conductivity with time for X above 0.8 can be explained in terms of the interference of the ion conduction by the PEa crystalline phase involving no salt. In the amorphous system, ion conduction follows the free-volume regime, i.e., carrier ions migrate through the free volume of the polymer correlating with the segmental motion. In this case, it is well known that as the Tg of the electrolyte becomes lower, the conductivity increases (2). Figure 2 shows that Tg decreases as X increases. Thus, the regime reasonably explains the finding that the conductivity increases with increasing X up to 0.6. It should be noted that a stable amorphous electrolyte with the composition of X = 0.6 and Y = 0.03 exhibits a high conductivity (2.68 • 10 -5 Scm -1 at 22~ which is approximately 3.7 times greater than that of the PEa-based polyurethane system (4).Decreasing Tg (15~ smaller than that of the polyurethane system) increases the carrier mobility and this fact may be partly responsible for this result. Also, it has been reported that the dissolving power for the alkali metal salts of poly(methacrylate) with short-side chains of EO (PMAEO) is greater than that of PEa (7). Probably the EO of PMAEO is mobile, compared to that of PEa, so that it more stably coordinates to the alkali metal ion. Accordingly, in this photocross-linked electrolyte, a similar effect increasing the carrier density can also be expected, since PEM is much shorter than PEa which is usually used and one of its ends is dangling. ConclusionsWe have examined a novel photocross-linked electrolyte of KCF3SO3-PEM-PED system. It has been found that the morphology and the conductivity of the system are greatly dependent on the composition (X), and that the conductivity reaches a value of 2.68 • 10 .5 Scm -1 at 22~ under optimal conditions. The large conductivity could be rationalized in terms of an increase in the carrier mobility (due to its low Tg) and an increase in the carrier density (due to the relatively large mobility of the EO chain). Also, being a transparent elastomer, this electrolyte seems to be very promising for electrochromic windows (8).Manuscript submitted July 27, 1987; revised manuscript received Dec. 14, 1987. Nippon Sheet Glass Company, Limited assisted in meeting the publication costs of this article. REFERENCES 1. P. V. Wright, Br. PoIym. J., 7,319 (1975 89, 987 (1985). 8. C.M. Lampert, Solar Energy Mater., 11, 1 (1984). ErratumIn the paper "Comparative Potentiodynamic Study of Nickel in Still and Stirred Sulfuric Acid-Potassium Sulfate Solutions in the 0.4-5.7 pH Range" by M.

Figure 10 shows the coulombic efficiency of Li/LiC104/ PPy batteries at various current densities. Each cell was charged to a 21% of doping level. Since the capacity of BF4--formed PPy is very low compared to the others, even the doping level of 21% is overloaded for this cathode. In fact, for even shallow charges, an extraordinary high cell voltage (over 4.5V) was observed, indicating that the PPy film is subject to oxidative decomposition. For this reason, the results for Li/LiCIO4/PPy formed with BF( are not shown. The battery assembled with the PPy cathode formed with PF6-keeps 100% of eouiombic efficiency up to the current density of 2.5 mAcm -2. From a high current density criteria better battery performance is also displayed in the order of PFC-, CF3803 -, CiO4 -formed PPy cathodes. In conclusion, the battery behavior of Li/LiCiO4/ pPy cell is consistent with the size and nucleophilicity of the polymerization anion. ABSTRACTThe potentiodynamic behavior of polycrystalline nickel disk electrodes in the potential range of the active to passive transition was investigated in still and stirred sulfuric acid solutions containing potassium sulfate in the 0.4 ~< pH ~< 5.7 range. Voltammetric data derived with a nickel rotating disk electrode allow a distinction between the main competing processes associated with the active to passive transition of nickel in acid, through their different dependences on the potential sweep rate and on the rotation speed. The first process corresponds to the formation of a nickel hydroxide solid phase through a relatively simple mechanism initially involving adsorbed (OH) species. The second process comprises the chemical dissolution and precipitation of nickel hydroxide, producing the thickening of the anodic layer. At high positive potentials, this anodic layer progressively transforms into the NiO passive layer. The overall reaction is discussed in terms of a complex reaction pathway in which the participation of water plays a fundamental role. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 169.230.243.252 Downloaded on 2014-11-27 to IP J. Electrochem. Soc.: ELECTROCHEMICAL SCIENCE AND TECHNOLOGY May 1988 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 169.230.243.252 Downloaded on 2014-11-27 to IP