Enhanced Electrocatalytic Oxygen Reduction on NiWOx Solid Solution with Induced Oxygen Defects.

The continuous solid solution NiWOx is successfully prepared by using precursor W18O49 with plenty of oxygen defects. The NiWOx nanoparticles are characterized by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray absorption spectroscopy. The crystallographic phase of NiWOx is stable and characterized by the same feature of the parent lattice W18O49 even with various concentrations of dopant Ni which indicates the existence of oxygen defects. The NiWOx nanoparticles could be processed as the appropriate promoter after loading 10 wt % Pt. The Pt/NiWOx displays remarkable response for oxygen reduction reaction in alkaline medium compared with the commercial Pt/C. The analysis of the electrochemistry data shows that the existence of abundant oxygen defects in the solid solution NiWOx is the key factor for the improved ORR catalyst performance. Ni is effective in the catalysts because of its compatibility with W in the solid solution and its active participation in oxygen reduction reaction.

Methanol electro-oxidation on platinum modified tungsten carbides in direct methanol fuel cells: a DFT study.

In exploration of low-cost electrocatalysts for direct methanol fuel cells (DMFCs), Pt modified tungsten carbide (WC) materials are found to be great potential candidates for decreasing Pt usage whilst exhibiting satisfactory reactivity. In this work, the mechanisms, onset potentials and activity for electrooxidation of methanol were studied on a series of Pt-modified WC catalysts where the bare W-terminated WC(0001) substrate was employed. In the surface energy calculations of a series of Pt-modified WC models, we found that the feasible structures are mono- and bi-layer Pt-modified WCs. The tri-layer Pt-modified WC model is not thermodynamically stable where the top layer Pt atoms tend to accumulate and form particles or clusters rather than being dispersed as a layer. We further calculated the mechanisms of methanol oxidation on the feasible models via methanol dehydrogenation to CO involving C-H and O-H bonds dissociating subsequently, and further CO oxidation with the C-O bond association. The onset potentials for the oxidation reactions over the Pt-modified WC catalysts were determined thermodynamically by water dissociation to surface OH* species. The activities of these Pt-modified WC catalysts were estimated from the calculated kinetic data. It has been found that the bi-layer Pt-modified WC catalysts may provide a good reactivity and an onset oxidation potential comparable to pure Pt and serve as promising electrocatalysts for DMFCs with a significant decrease in Pt usage.

[Chemical adsorption of thiosalicylic acid on silver surface investigated by surface-enhanced Raman scattering].

Surface-enhanced Raman scattering (SERS) of thiosalicylic acid (TSA) with sulfydryl group was investigated on the surface of electrochemically roughed silver electrode. The result shows that SERS enhancement effect was relative to the concentration and pH, and 1 x 10(-3) mol x L(-1) and pH 4 were the optimal condition. While the concentration increased, the enhancement effect decreased quickly because of steric hindrance. S--Ag peak position by the absorption of TSA was basically consistent, but pH significantly affected its intensity. The distribution and mechanism of TSA at different pH were further investigated. It was showed that TSA was adsorbed on the active silver surface via the sulfydryl group without H of neutral C4H4 (COOH)SH molecule. Competitive adsorption of negative valence C4H4 (COO-) SH and OH- may bring non-SERS under the strong base condition. At the same time, the sulfydryl group significantly influenced the carboxyl vibration peak's change and the distribution of electron cloud of benzene ring conjugate system.

WC@meso-Pt core-shell nanostructures for fuel cells.

We developed a facile method to synthesize core-shell WC@meso-Pt nanocatalysts by carburizing ammonium tungstate and copper nitrate via gas-solid reactions, followed by a Pt replacement reaction. The mesoporous nanocomposite displays higher activity and stability towards methanol electrooxidation than commercial Pt/C catalysts.

Kinetics of Fe(3)O(4)-CoO/Al(2)O(3) catalytic ozonation of the herbicide 2-(2,4-dichlorophenoxy) propionic acid.

The presence of Fe(3)O(4)-CoO/Al(2)O(3) can improve degradation efficiency significantly during the ozonation of the herbicide 2-(2,4-dichlorophenoxy) propionic acid (2,4-DP). The main factors affecting degradation efficiency, such as pH, the catalyst concentration and addition of the scavenger, were investigated. The kinetics of the catalytic ozonation are also discussed. The results indicate that two factors, the oxidation after adsorption of 2,4-DP and the oxidation of hydroxyl radicals (OH), lead to a great enhancement in ozonation efficiency during the catalytic ozonation of 2,4-DP in the presence of Fe(3)O(4)-CoO/Al(2)O(3), in which the oxidation of the OH plays an important role. Under controlled conditions, the apparent reaction rate constants for the degradation of 2,4-DP were determined to be 2.567 × 10(-4)s(-1) for O(3) and 1.840 × 10(-3)s(-1) for O(3)/Fe(3)O(4)-CoO/Al(2)O(3). The results from the analysis of the reaction kinetics using the relative method showed that O(3)/Fe(3)O(4)-CoO/Al(2)O(3) possessed a larger R(ct) (R(ct) is defined as the ratio of the ·OH exposure to the O(3) exposure, R(ct) = ∫C(t)(OH) dt/C(t)O(3)dt) than O(3), indicating that O(3)/Fe(3)O(4)-CoO/Al(2)O(3) produced more hydroxyl radicals.

[Oxidative efficiency of the system of electrolysis coupled ozonation].

The oxidation system of electrolysis coupled ozonation (electrolysis-ozonation) was used to degrade 4-chlorophenol (4-CP), and its mechanism was discussed on the basis of kinetic analysis. The experimental results indicated the electrolysis-ozonation system had a significant synergistic effect during degradation of 4-CP. For example, the electrolysis-ozonation had the 4-CP removal rate of 92.7% and the COD removal rate of 64.9% in 900 s, respectively; while electrolysis alone plus ozonation alone only had the 4-CP removal rate of 69.7% and the COD removal rate of 30.1% under the same conditions. The results of H2O2 concentration analysis and photocurrent test showed that the synergistic mechanism of electrolysis-ozonation included two factors: (1) production of *03- at the cathode; (2) H2O2 generation resulting from reduction of dissolved oxygen. The above two factors led to generation of *OH in system effectively.

[CuO-Ru/Al2O3 catalytic ozonation of acetophenone in water].

Two-component CuO-Ru based on active Al2O3 (CuO-Ru/Al2O3) catalyst was prepared by incipient wetness impregnation and used to catalytic ozonation of acetophenone (AP). The results showed that doping Ru could significantly improve the catalytic activity of CuO/Al2O3. For example, the COD removal rates of AP solution after 30 min by ozonation alone, CuO/Al2O3/O3, and CuO-Ru/Al2O3/O3 were 6.3%, 20.0% and 54.0%, respectively. The change of pH almost had no affect on degradation efficiency of AP. However, a comparison of COD removal between ozonation alone and catalytic ozonation indicated that CuO-Ru/Al2O3 catalyst was more suitable for application in neutral or acidic condition. CuO-Ru/Al2O3 catalyst could accelerate decomposition rate of ozone in water, and its decomposition rate constant reached 2.58 x 10(-3) s(-1) while that of ozone alone in double-water was 1.19 x 10(-3) s(-1). The experimental result of t-butanol indicated that CuO-Ru/Al2O3 catalytic ozonation of AP followed a radical-type mechanism.

Metal complexation and biodegradation of EDTA and S,S-EDDS: a density functional theory study.

The complexation reactions of ethylenediaminetetraacetate (EDTA(4-)) and S,S-ethylenediaminedisuccinate (S,S-EDDS(4-)) with Co(2+), Ni(2+), Cu(2+), Zn(2+), and Cd(2+) cations are investigated by using the DFT/B3LYP method. The hydration reaction of each metal ion with solvent water cluster is considered with a mixed cluster/continuum model. The subsequent metal complexation is treated as a substitution reaction of the coordinated water molecules by the amino polycarboxylic acid ligand. Thermodynamic cycles are schemed to evaluate the free energy changes for both hydration and complexation processes. The values of complexation free energy changes show that the stabilities of metal complexes with the isomeric ligands follow the order of [M(S,S-EDDS)](2-) in trans(O(6))-conformer < [M(S,S-EDDS)](2-) in trans(O(5))-conformer < [M(EDTA)](2-), implying that the failure to observe the trans(O(6)) conformer under experimental conditions is attributed to its inherent instability. The same trend appears in our steric strain analysis on the various chelate rings in complexes. Because the [M(S,S-EDDS)](2-) in trans(O(6)) complex is not available, we focus on the other two series of complexes with concerned metal ions. The stabilities decrease in the order Cu(2+) > Ni(2+) > Co(2+) > Zn(2+) > Cd(2+) and Cu(2+) > Ni(2+) > Co(2+) > Cd(2+) > Zn(2+) for trans(O(5))-[M(S,S-EDDS)](2-) and [M(EDTA)](2-), respectively. These two tendencies are shown to be consistent with the decrease in the metal-to-ligand charge transfer. Meanwhile, a good quantitative correlation is found between the complexation free energies and the dipole moments for all complexes (excluding the case of Cu(2+)). The far-infrared spectra are present to investigate the characteristics of metal-dependent vibrations, and the further natural bond orbital (NBO) method is taken to show the nature of metal-ligand bonding interactions. Finally, and perhaps most importantly, degrading products of both amino polycarboxylic acids are successfully predicted through calculating the dissociation energies of all C-N bonds in free EDTA, S,S-EDDS, and their successive products. Degradation mechanisms with intramolecular hydrogen transfer are proposed for the biodegradation reactions of S,S-EDDS and its product N-(2-aminoethyl) aspartic acid (AEAA).

[Kinetic and mechanism of ozonation of terephthalic acid].

The effect of ozonation of terephthalic acid (TA) was evaluated, and the kinetic and mechanism of this process were also discussed. The rate constants of TA with ozone and OH radicals calculated by the relative method are (0.047 +/- 0.010) L x (mol x s)(-1) and 2.28 x 10(9) L x (mol x s)(-1), respectively. The above result was in accordance with the apparent reaction rate constant of ozonation of TA when the process was controlled by chemical reaction. Intermediates detected by high-performance liquid chromatography (HPLC) and ion chromatography (IC) included benzoic acid, tartaric acid, formic acid and oxalic acid, therefore the possible destruction pathway of ozonation of TA was proposed on the basis of above results.

[Deactivation mechanism of Pt anode in the process of electroxidation of p-chlorophenol].

Deactivation of Pt electrode in the process of electroxidation of p-chlorophenol (p-CP) was investigated using linear sweep voltammetry, LC/MS and spectrum analysis techniques. The experiment results indicated that Pt would lose its electro-catalytic activity soon because polymer formed at the electrode surface. The in-site IR spectra of Pt showed two weak absorption bands appeared at 1 200 and 1 800 cm(-1) during the oxidation of p-CP, which are characteristics of aromatic ether and carbonyl group, respectively. Increasing initial concentration of p-CP and pH value of solution would accelerate the deactivation speed of Pt. Acetonitrile lixivium for deactivated Pt was analyzed by LC/MS, and it was found that the polymers formed at the surface of Pt were some mixed compounds. The mechanism of polymerization includes the following ways: coupling reaction of organic radical each other; substituting reaction of organic radical with p-CP (or intermediates or small polymers).

[Indirect determination of stability constant of zinc cystine chelate by flame atomic absorption spectrometry with ZnS].

Cystine was indirectly determined by flame atomic absorption spectrometry with ZnS. Base on the determination mechanism, the composition of complex, the complex balance reaction of soluble zinc ion, which formed in the determination of cystine by FAAS, and the stability constant of complex balance were discussed in the present paper. Under the alkalescent conditions, cystine (Cys-Cys) can react with zinc sulfide suspension solution to form a soluble complex or chelate of zinc cystine. The maximum concentration was reached at pH 9.4 and the quantity of the chelate was determined by flame atomic absorption spectrometry with zinc sulfide. The stability constants of the complex compound of zinc cystine were studied successfully, after the numeric measurements and theoretical investigations under the best-optimized acidity for determination. In conclusion, at the best optimized acidity pH 9.4, the stability constant of alkalescent zinc cystine is between 9. 542 x 10(32) and 10.353 x 10(32), the average value is betaw = 9.916 x 10(32), and log betaw = 32.996. The standard deviation is 0.301 x 10(32). It is shown that the atomic absorption spectrometry can be used not only for the determination of trace elements and the indirect determination of organic compound, but also for the study of physical configuration and the determination of physical constant of complex ion.

[Study on the mechanism of ozonation of organic combination with UV radiation].

Nitrobenzene, glycolic acid and acetic acid were selected to be degraded by O3/UV. During the degradation of nitrobenzene by O3/ UV, addition of MnO2, an effective catalyst to decompose H2O2 in water, decreased the degradation efficiency obviously, and the degradation efficiency of O3 /UV was even lower than that of ozonation alone, for example, the TOC removal rates of nitrobenzene by O3 /UV, O3 and O3/UV + MnO2 were 44% , 41% and 39% in 40 minutes, respectively. These results demonstrate that intermediate H2O2 plays an important role in enhancement of degradation efficiency of O3/UV. Furthermore, the characteristic of organic, which acts as promoter or inhibitor in the process of ozonation, also affects the degradation efficiency of O3/UV directly, when glycolic acid, a promoter in ozonation, was degraded, the combination UV radiation with ozonation could remove it efficiency, the removal rate of glycolic acid reached 76% in 30 minutes; however, when acetic acid, an inhibitor in ozonation, was degraded by O3/UV, the removal rate of acetic acid was very low, which was similar with that of ozonation alone.

[Studies of laser Raman spectra of sodium glutamic acid solution effected with environmental light].

The laser Raman spectra influenced by environmental light have been studied in the determination of sodium glutamic acid solution. The environmental light included natural light from outdoors and the light from indoor fluorescents. The results show that different influences on laser Raman spectra of sodium glutamic acid solution can be produced in different environmental light. There were some characteristic spectral lines, minus peaks or sharpened peaks. These influences cannot be ignored. The determinations of laser Raman spectra must be performed in darkroom or in the sheathing or mantle etc.

[Studies of interference source in laser Raman spectra of near infrared].

Many abnormal peaks in laser Raman spectra were found in determinations with laser illuminant of 785. 18 nm. After studies, it was found that the notch filter caused the interferences and the characteristics of the band pass filter were not good. The absorption spectral characteristics of notch filter were studied for the new and old of band pass filters.

Label-free and reagentless aptamer-based sensors for small molecules.

A label free, reagentless aptasensor for adenosine is developed on an ISFET device. The separation of an aptamer/nucleic acid duplex by adenosine leads to the aptamer/adenosine complex that alters the gate potential of the ISFET. The sensitivity limit of the device is 5 x 10-5 M. Also, the immobilization of the aptamer/nucleic acid duplex on an Au-electrode and the separation of the duplex by adenosine mono-phosphate (AMP) enable the electrochemical detection of adenosine by faradaic impedance spectroscopy. The separation of the aptamer/nucleic acid duplex by adenosine and the formation of the aptamer/adenosine complex results in a decrease in the interfacial electron-transfer resistance in the presence of [Fe(CN)6]3-/4- as redox active substrate.

[Influence of different light source on the laser Raman spectra in determination of sodium glutamic acid].

The influences of different laser source and different light power on laser Raman spectra were studied for the sodium glutamic acid. The results show that some influences existed using different wavelength and power of light source the peak shifting 6 cm(-1). As UV laser has great light power, the samples were destroyed, making the Raman spectra- reduce or disappear. The attenuation of light was needed. The linear relation existed between the Raman intensity and the power of laser light source, and the correlation coefficient was more then 0.999. The Raman intensity per light power unit was related to the wavelength, and was not related to the power of laser source.

[Studies of complexing action mechanism in the indirect determination of arginine by FAAS with ZnS].

Each state of arginine and zinc ion in aqueous solution under different pH conditions was calculated by computer, giving out the scattergram. After the investigation, the mechanism of complexing action in indirectly determining arginine by flame atomic absorption spectrometry with ZnS was studied in terms of the influence of solution pH. It is with different state of arginine and zinc ion in aqueous solution in differential pH that the response peak with pH in given conditions is obtained. The reason for forming the left peak is different from the reason for forming the right peak. The soluble complexing ion is composed of + 1 valence arginine Arg+ + - and Zn(OH)2. The theoretical analysis from computing and scattergram dovetails very well the data determined from the experiments. The structure of complexing ion is [HN[double bond]CH(NH3+ )--NH--(CH2)3--CH(NH3+)--COO]2Zn(OH)2.

[Studies of influences of environmental light on near-infrared laser raman spectra of sodium glutamic acid solution].

The near-infrared laser Raman spectra influenced by environmental light were studied in the determination of sodium glutamic acid solution. The environmental lights included natural light from outdoors and light from room fluorescent lamp. The results show that different influences on near infrared laser Raman spectra of sodium glutamic acid solution can be produced in different environmental light. There were some characteristic spectral lines, down peaks or sharpened peaks. These influences cannot be ignored. It is suggested that the determination of solution by near-infrared laser Raman spectra is carried out in dark-room or in dark cover to completely isolates the influences of the environment lights.

[Study on dechlorination of p-chlorophenol by Ni/Fe bimetallic particles].

Dechlorination property of p-chlorophenol (p-CP) by Ni/Fe bimetallic particles was studied in this work. The experimental results show that adsorbed hydrogen atom is the main reductive agent for dechlorination of p-CP and chemical reaction at the surface of catalyst is the rate-determing step in this process. The catalyst with mass ratio of 2.96% Ni had the largest specific surface area and also had the highest dechlorination efficiencies (64% in 90 min) under the same conditions. The apparent kinetics of p-CP dechlorination by Ni/Fe was the first order reaction and apparent rate constant (kappa) was proportional to the specific surface of catalyst. The apparent rate constant per specific surface area (kappa') was also calculated (7.61 x 10(-4) min(-1) m(-2)). Temperature was also an important parameter in this system. The dechlorination efficiency was proportional to temperature when it is below 43 degrees C, when temperature exceeded 43 degrees C, increasing temperature had inverse effect on dechlorination efficiency.

Hexalithium hexadecahydrate decavanadate, [Li6(H2O)16V10O28]n.

The novel title compound, poly[octa-mu-aqua-octaaqua-mu-decavanadato-hexalithium], contains [V10O28]6- polyanions with 2/m symmetry linked by centrosymmetric [Li6(H2O)16]6+ cation chains. The [V10O28]6- polyanions form a two-dimensional network with [Li6(H2O)16]6+ chains via O-polyanion-Li-chain coordination, with Li-O bond lengths in the range 2.007 (5)-2.016 (5) A. The hexalithium hexadecahydrate chain is composed of a centrosymmetric pair of LiO6 octahedra and four distorted LiO4 tetrahedra. Hydrogen bonds occur between the polyanion and the Li-based chains, and within the Li-based chains.