In situ FTIRS studies of kinetics of HCOOH oxidation on Pt(110) electrode modified with antimony adatoms

The electrochemical behavior of irreversibly adsorbed antimony on a Pt(110) electrode (Pt(110)/Sb) with various coverages was studied using cyclic voltammetry. The kinetics of HCOOH oxidation via reactive intermediates on Pt(110)/Sb were investigated quantitatively by employing the potential step technique and in situ FTIR spectroscopy. The results demonstrated that Sb adatoms were stable on Pt(110) when the electrode potential was below 0.45 V (SCE). It has been revealed that the dissociative adsorption of formic acid can be inhibited by the presence of Sb_ad on the Pt(110) surface. The electrocatalytic effects of Sb_ad towards HCOOH oxidation consist in a negative shift of the oxidation potential (about 350 mV) and the enhancement of the oxidation current. Based on the data processing method of integration transform developed in our previous papers, the kinetics of HCOOH oxidation on Pt(110)/Sb electrodes of different θ_Sb have been investigated quantitatively, and both the rate constant k_f and the transfer coefficient β were determined and reported.     

Modelling the Oxidation of CO at the Interface of Heterophase Metal Catalysts

CO oxidation on a surface composed of two types of patches was simulated by the Monte Carlo method. Each patch has kinetic properties close to those of Pt(100) and Rh(100). The reaction rate was shown to increase significantly at the interface, involving CO_ads on platinum and O_ads on rhodium, under particular conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Kinetics and Mechanism of the Autocatalytic Oxidation of Mn(II) by Bromine

The oxidation of Mn(II) by bromine is an autocatalytic reaction, which seems to be important for a detailed elucidation of chemical oscillators, based on manganese chemistry. With regard to the mechanism proposed previously, an alternative reaction mechanism is proposed, based on a micro-heterogeneous oxidation of Mn(II) ion, adsorbed on a surface of the MnO₂ colloid. This revised version was published online in June 2006 with corrections to the Cover Date.     

Low-Temperature CH4 Total Oxidation on Catalysts Based on High Surface Area SnO2

Pure SnO₂, sulfated SnO₂-SO₄ ^2- and Pd supported on SnO₂ and SnO₂-SO₄ ^2- were prepared from SnO₂ precursor with high surface area, and used for CH₄ deep oxidation. The catalysts were characterized by means of N₂-BET, XRD, TG-DTA, XPS and TPD. SnO₂-SO₄ ^2- shows higher activity than SnO₂, due to the presence of more active oxygen species, superacid sites and its higher BET surface area. Pd/SnO₂ and Pd/SnO₂-SO₄ ^2- display essentially the same activity to each other, while it is much higher than the activity on SnO₂ and SnO₂-SO₄ ^2-. The main reason is ascribed to the concerted action between Pd and the supports.     

Aerobic oxidation of oct-1-ene in a nanoscale microreactor

Nanoscale microreactors containing the Pd(II)/Pd(0)–1,4-benzoquinone/hydroquinone–CoSalophen _OX/ CoSalophen triple catalytic system were constructed in the supercages of zeolite Y. This catalytic system works as a closed reactor and is capable for the highly selective palladium-catalyzed oxidation of oct-1-ene to octan-2-one with molecular oxygen at room temperature.     

Syntheses of amphiphilic block copolymers by living cationic polymerization of vinyl ethers and their selective solvent‐induced physical gelation

Amphiphilic diblock copolymers were prepared by the living cationic polymerization of vinyl ethers in the presence of added bases, and their selective solvent‐induced physical gelation behavior was investigated. The block copolymerization of 2‐phenoxyethyl vinyl ether (PhOVE) and 2‐methoxyethyl vinyl ether (MOVE) was carried out in the presence of ethyl acetate with Et_1.5AlCl_1.5 in toluene at 0 °C. Despite the rate difference, diblock copolymers with a very narrow molecular weight distribution were obtained, quantitatively. By adding the selective solvent, water, to the acetone solution of the diblock copolymer, PhOVE₂₀₀‐b‐MOVE₄₀₀, physical gelation occurred suddenly and the system ceased to flow, maintaining transparency. Viscoelastic measurements and transmission electron microscopic observations were performed to examine the characteristic gelation behavior and structure of the obtained gels. Various gelation conditions and physical gelation by other amphiphilic block copolymers were also designed on the basis of the solubility of each block segment. Further, new forms of physical gelation, accompanied by the solubilization of immiscible organic compounds, were achieved using similar diblock copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3190–3197, 2001     

Photocatalytic Effects of Rutile Phase TiO2 Ultrafine Powder with High Specific Surface Area Obtained by a Homogeneous Precipitation Process at Low Temperatures

The photocatalytic characteristics of nanostructured TiO₂ ultrafine powder with rutile phase produced using the homogeneous precipitation process at low temperatures (HPPLT) were compared with those of commercial P-25 TiO₂ powder by flame hydrolysis. The TiO₂ powder by the HPPLT showed much higher photoactivity in the removal rate, showing lower pH values in the solution than the P-25 powder when eliminating metal ions such as Pb and Cu from the aqueous metal-EDTA solutions. This can be inferred as the more rapid photo-oxidation or -reduction of metal ions from the aqueous solution, together with relatively higher efficiencies in the use of an electron-hole pair formed on the surface of the TiO₂ particles under UV light irradiation. Also, in the view of the TiO₂ particle morphology, compared to the well-dispersed spherical P-25 particles, the agglomerated TiO₂ secondary particles by the HPPLT consist of acicular typed primary particles with a thickness in the range of 3–7 nm and the primary particles radialize in all directions, which would be more effective to photocatalytic reactions without the large electron-hole recombination on the surface of the TiO₂ particle under UV light irradiation. It can be, therefore, thought that the higher photoactivity of the rutile TiO₂ powder by the HPPLT in the aqueous solutions results mainly from having a larger surface area by the acicular shaped primary particles with very thin thickness and radialization in all directions.     

肾上腺素电氧化过程的快速扫描循环伏安研究

以快速循环伏安法为主要手段,研究了肾上腺素电化学氧化反应机理.肾上腺素在1 m ol•dm－3 H2SO4中的电化学氧化反应,具有扩散控制的基本特征,并伴随着电活性质粒的 弱吸附现象.在快速电势扫描条件下,肾上腺素电氧化过程遵从EC反应机理.当肾上腺素浓度低于1.00×10－3 mol•dm－3时,吸附现象的特征趋于显现出来;在快速电势扫描速率下,电活性质粒吸附的特征更加明显.结合表面伏安法分析,估算了肾上腺素电氧化过程的传递系数α=0.264.电化学反应速率常数ks=31.81 s－1.     

Enantioselective Allylic Oxidation of Olefins Using Chiral Quinolinyl‐oxazoline Copper Complex Catalysts

Copper complexes of chiral quinolinyl‐oxazoline have been studied as the catalysts for enantioselective allylic oxidation of cycloalkenes with tert‐butyl perbenzoate. Using 5 mol% of these chiral catalysts, optical active allylic benzoates were obtained in moderate enantiomeric excesses. CuOTf prepared in situ, CuClO₄ and CuPF₆ were found to be good precatalysts in acetone.     

Syntheses and Properties of New Pendant‐armed Calix[4]arene Derivatives as Cesium Selective Ionophore

Two new pendant‐armed calix[4]arene derivatives 5 and 6 have been synthesized. The study of alkali metal picrates extraction indicates that both compounds show preference of cesium cation, compound 6 in 1,3‐alternate conformation has better extractibility for Cs⁺ than compound 5. The coordination behavior of compound 6 with cesium cation was studied by ¹H NMR spectroscopy. The Cs⁺ selective electrode based on compound 6 exhibits a linear, near Nernstian response characteristics, the slope is 56.4 mV/decade in me concentration range of 10^?4—10^?1 mol/L, the selectivity coefficient (logK^pot_Cs.Na) is ?3.39.