掺杂NiO的Ni(OH)2电化学性能研究

于Ni(OH)2中添加具有电容特性和大电流充放电性能良好的NiO.研究发现掺杂5%NiO的Ni(OH)2在0.2C倍率下放电容量可达310.1mAh/g,而3C放电容量还可以保持79.5%.其循环伏安扫描氧化还原峰电位差仅为164mV,表明该材料的循环可逆性好.由此可见在Ni(OH)2掺杂适量的NiO,对于Ni(OH)2的大电流充放电性能确有改进作用.     

Self-aggregates of hydrophobically modified poly(2-hydroxyethyl aspartamide) in aqueous solution

Dehydrocholic acid (DHA) grafted poly(2-hydroxyethyl aspartamide) (PHEA)s were successfully synthesized and their self-aggregates in aqueous solution were characterized by fluorescence spectra and light scattering. PHEA was obtained by a simple reaction of ethanolamine with synthesized poly(succinimide) (PSI), and then PHEA-g-DHA was synthesized through an ester linkage between DHA and PHEA. The degree of substitution (DS) of DHA groups, defined by grafted mole%, was determined from both ¹H-NMR and elemental analysis. The grafting reaction of DHA was retarded up to almost 10 mole% feed ratio of DHA/PHEA, but increased linearly above the threshold ratio. Nano-size self-aggregates in aqueous solution were examined with four DSs less than 10. As DS increased, the critical aggregation concentrations (CAC) of polymers were continuously reduced and the size of primary aggregates reduced to as small as 40 nm in diameter. When stored, the sonicated aggregates of high DS were destabilized, apparently forming large aggregates with small curvatures. The formation of irreversible interfused secondary structures would be induced by the curvature change or aggregation of primary particles. A simple calculation indicates that a small change of separation between grafted DHA groups may induce the large curvature shift, in fact, sphere-to-planar surface transition.     

Oxidation of UO2(s) in aqueous solution

In this review the kinetics and mechanism of oxidative dissolution of UO₂(s), mainly under conditions of relevance for the safety assessment of a deep geological repository for spent nuclear fuel, are discussed. Rate constants for the elementary processes involved (oxidation of UO₂ and dissolution of oxidized UO₂) are used to calculate the rates of oxidative UO₂(s) dissolution under various conditions (type of oxidant, oxidant concentration and HCO₃ ⁻/CO₃ ²⁻ concentration) for which experimental data are also available. The calculated rates are compared to the corresponding experimental values under the assumption that the experimental numbers reflect the steady-state conditions of the system. The agreement between the calculated rates and the corresponding experimental ones is very good, in particular for the higher rates. In general, the calculated rates are somewhat higher than the experimental numbers. This can be due partly to the use of initial concentrations rather than steady-state concentrations in the calculations. The kinetic data are also used to quantitatively discuss the dynamics of spent nuclear fuel dissolution under deep geological repository conditions.      

Fabrication of beta-Ni(OH)2 and NiO hollow spheres by a facile template-free process

Ni(OH)2 hollow microspheres with beta-Ni(OH)2 nanosheets as the in situ formed building units were fabricated via a novel template-free approach in a strong alkaline solution of glycine, and can be converted into NiO hollow microspheres by a thermal decomposition process.     

Electrosynthesis of pyrazole-4-carboxylic acids by oxidation of 4-formylpyrazoles on NiO(OH)-electrode in aqueous alkaline solution

Electrochemical oxidation of di- and trisubstituted 4-formylpyrazoles on a Ni-anode in aqueous alkali led to the formation of the corresponding pyrazole-4-carboxylic acid in 60–90% yields. The yields of the target products depend on position of substituent in the pyrazole ring and are decreased in the following sequence of substituent at position 1 Me > Et > Ph, as well as when the aqueous medium was replaced with aqueous alcohol (50% Bu^tOH). Oxidation of 4-formylpyrazoles containing Me groups at the carbon atoms of the pyrazole ring led, to monoacids and also pyrazoledicarboxylic acids in small (1.5–14%) amounts; the latter were the oxidation products of the aldehyde and the Me groups.     

Interpolymer complexes of poly(acrylic acid) with poly(2-hydroxyethyl acrylate) in aqueous solutions

Complexes formed from poly(acrylic acid) and poly(2-hydroxyethyl acrylate) were studied in aqueous solutions by viscometric, turbidimetric, FTIR spectroscopic, and thermogravimetric analysis methods. The formation of interpolymer complexes stabilized by hydrogen bonds was observed. It was found that the compositions of these interpolymer complexes are strongly dependent on the concentration of polymers, the order of mixing the solutions, and the pH. It was demonstrated that the complexation ability of poly(2-hydroxyethyl acrylate) is relatively low compared to other known nonionic water-soluble polymers. However, it can be significantly increased via hydrophobic modification of the poly(acrylic acid) using cetyl pyridinium bromide.     

Voltammetric determination of mercury(II) at a carbon paste electrode in aqueous solutions containing tetraphenylborate ion

The determination of mercury(II) ions can be achieved by monitoring the decrease in the oxidation peak of the tetraphenylborate ion in the presence of this metal ion at a carbon paste electrode. The reaction between mercury(II) and the tetraphenylborate ion results in the formation of diphenylmercury, thus providing the method with good selectivity over other metal ions. Using anodic stripping voltammetry in a neutral electrolyte, a linear dependence of the decrease of peak height was observed on increasing the mercury(II) concentration in the range 1 x 10(-6)-8 x 10(-9)M mercury(II). Zinc(II), cadmium(II), lead(II), nickel(II), cobalt(II), tin(II), potassium(I) and ammonium(I) ions did not interfere at a 1000-fold concentration excess. Iron(III) and chromium(III) did not interfere at a 250-fold and 50-fold concentration excess, respectively. Following masking procedures, copper(II), bismuth(III) and silver(I) did not interfere at a 100-fold concentration excess. The method can be used to determine the concentration of mercury(II) in natural waters contaminated by this metal.     

The conformational stability of tactic poly(2-hydroxyethyl methacrylate) in aqueous salt solutions

The conformational stability of tactic poly(2-hydroxyethyl methacrylate) (PHEMA) in aqueous salt solutions was investigated by measurements of swelling, surface-free energy, and differential scanning calorimetry, as this polymer in water is sensitive in various electrolytes. In the case of inorganic salts, the major role for the salt effect is played by the anions, and the exposure of hydrophobic components at the PHEMA surface can be correlated with the increase of the degree of swelling. The influence of cations is considerably weaker. In the case of organic salts, tetraalkylammonium halides cause the chain extension more effectively with the increase of alkyl chain length in the cations. This result indicates that the breakdown of the hydrophobic parts in PHEMA provides an important clue on conformational stability. The amount of water molecules bound with the hydrophilic sites of tactic-PHEMA mainly depends on the chain extension and the hydration of cations. Since the sites in tactic-PHEMA influenced by the cation and the anion are different, their effects cause the conformational transition at a specific range of salt concentration. © 1993 John Wiley & Sons, Inc.     

Oscillatory electrocatalytic oxidation of methanol on an Ni(OH)2 film electrode

A film of Ni(OH)₂ deposited cathodically on a roughened nickel substrate consists of even nanoparticles, which were characterized by atomic-force microscopy (AFM). The mechanism of potential oscillations in the electrocatalytic oxidation of methanol on this film electrode in alkaline medium was studied in situ by means of Raman spectroscopy in combination with electrochemical measurements. The redox change of the nickel hydroxide film, the concentration distribution of methanol in the diffusion layer, and the oxidation products of methanol were characterized in situ by time-resolved, spatial-resolved, and potential-dependent Raman spectroscopy, respectively. Electrochemical reactions, i.e. methanol oxidation and periodic oxygen evolution, coupling with alternately predominant diffusion and convection mass transfer of methanol, account for the potential oscillations that occur during oxidation of methanol above its limiting diffusion current. This mechanism is totally different from that of methanol oxidation on platinum electrodes, for which surface steps, i.e. formation and removal of CO_ad, are essential.This work is dedicated to Professor Gyorgy Horanyi on the occasion of his 70th birthday in recognition of his numerous contributions to field of electrochemical oscillations and electrocatalysis at Ni-hydroxide electrodes.     

Potentiometric behaviour of the copper electrode in aqueous copper(II) perchlorate solutions containing sodium chloride

It is demonstrated that the copper metal electrode corrodes in the presence of copper(II) ions in solution. A model based on mass balance can properly describe the experimental results. In the presence of copper(II) ions the copper electrode responds to copper(I), indicating that the electrode potential corresponds to a mixed potential.     

CdTe@Co(OH)2 (core-shell) nanoparticles: aqueous synthesis and characterization

A seed-mediated growth approach for preparation of multifunctional CdTe@Co(OH)2 (core-shell) nanoparticles in the aqueous phase is reported.     

Poly(2-hydroxyethyl acrylate) hydrogels containing hyper-branched poly(amidoamine) for sustained drug release

Hydrogels containing hyper-branched poly(amidoamine) (hb-PAMAM) microenvironments were suggested for the sustained release of ionizable drugs. For this purpose, a series of poly(2-hydroxyethyl acrylate) (PHEA) hydrogels containing hb-PAMAM (PHEA-hb-PAMAM) were prepared by copolymerization of 2-hydroxyethyl acrylate with acryl-terminated hb-PAMAM. The hb-PAMAM was synthesized by the Michael addition reaction of triacryloylhexahydro-1,3,5-triazine (TT) and piperzaine (PZ). By using nonionic Tegafur and ionizable salicylic acid (SA) as model drugs, the release mechanisms of drugs from PHEA-hb-PAMAM hydrogels were investigated. Compared with the release kinetic of Tegafur, the release rate of SA from the hydrogels was evidently slowed down. Moreover, the release rate of SA can be modulated by the addition of salt. This can be attributed to the ionic interaction of SA with hb-PAMAM microenvironments. By analyzing the release kinetics of SA from the hydrogels, it was found that the release of SA followed non-Fickian diffusion.     

Electrochemical behavior of ammonia at Ni/Ni(OH)2 electrode

The electrochemical oxidation of ammonia was investigated on a Ni/Ni(OH)₂ electrode prepared by potential cycling of a Ni electrode in 1 M NaClO₄. It was found that oxidation of ammonia is strongly pH dependent and proceeds mainly at pH values above 7. This indicates that NH₃ rather than ${\text{NH}}_4^{+}$ is oxidized on nickel electrodes. Oxidation of ammonia occurs in the potential region of Ni(II)/Ni(III) redox activity resulting in formation of a clear peak. Ni/Ni(OH)₂ is not deactivated during ammonia oxidation even at high ammonia concentrations. A considerable fraction of the ammonia was oxidized to nitrate (11%), while the rest were gaseous nitrogen compounds. It is postulated that nitrogen was formed via a mechanism involving direct electron transfer from ammonia to the anode whereas the formation of nitrate involved oxygen transfer from water to an ammonia molecule.     

Electrocatalytic oxidation of formaldehyde and methanol on Ni(OH)2/Ni electrode

A nickel hydroxide-modified nickel electrode (Ni(OH)₂/Ni) was successfully prepared by the cyclic voltammetry (CV) method and the electrocatalytic properties of the electrode for formaldehyde and methanol oxidation have been investigated respectively. The Ni(OH)₂/Ni electrode exhibits high electrocatalytic activity in the reaction. A new method has been developed for formaldehyde determination at the nickel hydroxide-modified nickel electrode and the experimental parameters were optimized. The oxidation peak current is linearly proportional to the concentration of formaldehyde in the range of 7.0 × 10^?5 to 1.6 × 10^?2 M with a detection limit of 2.0 × 10^?5 M. Recoveries of artificial samples are between 93.3 and 103.5%. The effect of scan rate and methanol concentration on the electrochemical behavior of methanol were investigated respectively.     

Oxidation of 4-methyl-4-(2-hydroxyethyl)-1,3-dioxane to 2-hydroxy-2-methylglutaric acid

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, p. 1284, September, 1988.