Advanced Materials Research Vols. 781-784

Abstract: Preparation of chlorine dioxide by electrocatalytic reduction of sodium chlorate with Ti/IrO₂ anode and Ti cathode was studied in a three-electrode cell without any diaphragm but with a sandwich bath by galvanostatic electrolysis. Classic iodometry was used to determine the concentration of ClO₂ in the electrolyte. The change of space-time yield with current density, the concentration of H₂SO₄, the concentration of NaClO₃, reaction temperature and electrolysis time were studied through single factor experiment in order to determine the optimal conditions of electrolysis. It shows that the optimal conditions of ClO₂ preparation by electrocatalytic reduction of sodium chlorate were: i=60 mA/cm², [H₂SO₄]=4.5 mol/L, [NaClO₃]=1.0 mol/L, T=30 °C, t=30 min. Under these conditions, the space-time yield of ClO₂ reached 1.50 mg/L·s.

Abstract: The effect of tartaric acid on the electrochemical behavior of K₃[Fe(CN)₆] was investigated on bare ITO electrodes, electrodes coated with multi-walled carbon nanotubes possessing carboxyl groups (MWNT-COOHs), and electrodes coated with cyclodextrin modified multi-walled carbon nanotubes (MWNT-CDs), respectively. It is found that the molecular chirality of tartaric acid can hardly influence the electrochemical behavior of K₃[Fe(CN)₆] on bare ITO electrodes. When the electrodes coated with MWNT-COOHs are used, the effect of the molecular chirality becomes distinguish. In the case of the electrodes coated with MWNT-CDs, the enhanced chiral discrimination between D-tartaric acid (D-TA) and L-tartaric acid (L-TA) can be observed. The control step in the electrochemical reaction of K₃[Fe(CN)₆] on the electrodes coated with MWNT-CDs is deduced to be different when D-TA or L-TA is introduced into the solution, respectively. Therefore, the enhanced chiral discrimination on the electrodes coated with MWNT-CDs is probably due to the change of the control step in the electrochemical reaction of K₃[Fe(CN)₆] caused by the chiral recognition of cyclodextrin moieties to D-TA and L-TA.

Abstract: Anatase TiO₂ nanotube arrays with about 50nm pore diameter were prepared by anodic oxidation. The effect of the donor materials (sodium hydroxide, methanol and ethylene glycol) on electrochemistry impedance spectroscopy (EIS) and the photocurrent responses of TiO₂ nanotube arrays photoanode in the photoelectrochemical cell for splitting water hydrogen production were investigated. The results indicate that all the donor materials enhance the photocurrent responses and reduce the internal reaction resistances of the TiO₂ nanotube arrays photoanode. The effect of adding organic donor compounds in the anolyte on charge transfer and photocurrent is superior to the inorganic donor compounds and in turn reduces from the ethylene glycol, methanol to sodium hydroxide. Additionally, it should be highlighted that +0.3V vs. open circuit potential of applied potential on the electrode promotes a suitable charge transfer at semiconductor/electrolyte interface. The flat band potentials of TiO₂ nanotube arrays photoanode move to negative direction with donor materials adding in the anolyte which indicates beneficial photoelectrocatalytic hydrogen production by water splitting.

Abstract: The effect of irradiation with heavy ions Ne, Ar, and Kr of various energies on the structure and properties of ceramic barium cerate doped with neodymium and annealed in air at 650°C for 7 hours is studied. It is noted that blistering was observed on cerate surface during its irradiation by low energy Ne ions, whereas it was not observed under low-energy Ar and Kr ions irradiation. Irradiation of the cerate with high energy ions caused partial amorphization of the irradiated surface of the material, while the structure of the non-irradiated surface did not change. In addition, the irradiated surface of the cerate endured solid-phase structural changes. Thus, upon high-energy ions irradiation in the range of Ne, Ar, Kr the cerate surface resembled the stages of spherulite formation - nucleation, growth (view of cauliflower), formation of spherulitic crust, respectively. The increase in water molecules release and reduction of molecular oxygen release from the barium cerate, irradiated by high-energy ions is found during vacuum constant rate heating. It is concluded that cerates undergo changes to the distances significantly exceeding the ion ranges in these materials. Features of high-energy ions influence on thermal desorption of carbon dioxide from cerates show, apparently, the formation of weakly bound carbonate compounds on the cerate surface in the irradiation process.

Abstract: The electrochemical reduction of carbon dioxide (CO₂) has been studied on various metal electrodes including main group and transition elements in aqueous solution. Of these electrodes, silver and gold are found to have catalytic activity for the conversion of CO₂ to CO with considerably high Faradaic efficiencies. However, no work has been done to evaluate the electrocatalytical property of these two electrodes in the same electrochemical system under the same condition. In present work, we investicate the electrocatalytical property of Ag and Au electrodes in the same electrolysis cell and under the same condition. We found Au electrode exhibits higher current density and higher faradaic efficiency for CO formation than Ag electrode.

Abstract: The article deals with the process of electrochemical dissolution of zinc polarization by alternating current of 50 Hz frequency in a solution of sodium sulfate. The influence of various parameters on the current efficiency of zinc dissolution was considered: the current density on the titanium and zinc electrodes, electrolyte concentration, duration of electrolysis and temperature of electrolyte. It was shown that at change of current density on the titanium electrode from 10 kA/m² up to 70 kA/m² current efficiency of zinc dissolution increases (55%), and further down. At change of current density of zinc electrode from 200 A/m² to 800 A/m², electrolysis time from 0.25 to 2.0 hours and increase of temperature from 20°C to 80°C the current efficiency of dissolution decreases and with increasing concentrations of sodium sulphate increases to 90%. Based on the results shown it is possible to create a waste-free synthesis of zinc compounds from environmental harmful residues of zinc metal by electrochemical technology.

Abstract: At present, indirect effects of high-voltage electrostatic field on organisms and biological materials have been extensively studied. However, the investigations on direct interaction between the electrostatic field and enzyme are scarce. In this paper, the direct effect of high-voltage electrostatic field on the LP and the protective effects of sucrose fatty acid ester on the activity of enzyme in high-voltage electrostatic field have been experimentally investigated. The results show that, high-voltage electrostatic field has direct effects on the LP and the best condition to enhance the activity of enzyme can be obtained. When the electric-field strength is low, with the increasing of the electric-field strength, the activity of the LP will be weakened. When the electric-field strength exceeds a certain level, the activity of the LP will be enhanced with the increasing of electric-field strength. For too higher electric-field strength , the activity of the LP will be again weakened with the increasing of electric-field strength. The sucrose fatty acid ester in low concentration provides a proper hydrophobic microenvironment for enzyme, which leads to the enhancement of enzyme's activity, while sucrose fatty acid ester in high concentration leads to the weakening of enzyme's activity. Moreover, sucrose fatty acid ester in enzyme solutions has protective effects on enzyme in the electric field and can reduce the impacts of high-voltage electrostatic field on the LP.

Abstract: This paper proposes a hypothesis of hydration. It assumes that the solute in the electrolyte solution exists as molecules, and each solute molecule is surrounded by h water molecules. On this basis, this paper deduces the activity coefficient formulas, and the model is applied to binary electrolyte solutions at room and elevated temperatures.

Abstract: In this paper, based on the ultrasonic dispersion principle, the grafting reaction of maleic anhydride (MAH) onto solid PP in water was studied with acetone as the phase physiognomy solvent, ammonium persulfate [(NH4)2S2O8] as the initiator. The influence of specific surface area on the graft ratio was also studied. The results showed that the grafting reaction had obvious relationship with the specific surface area of original PP particles.

Abstract: Polyacrylate microsphere with different core/shell ratio (mass ratio) were prepared by semi-continuous seed emulsion copolymerization using butyl acrylate (BA) and methyl methacrylate (MMA) as main monomers，which were used to toughen polylactic acid (PLA) after drying. The effect of core/shell ratio of polyacrylate toughening agent (ACR) on mechanical properties of PLA was studied. The results showed that when adding 8wt%ACR, the impact strength and elongation at break of PLA were both first increased and then decreased as increasing of core/shell ratio, while the tensile strength loss of PLA was little changed. It is found that the impact strength was increased about 24% than that of neat PLA as well as the elongation at break was increased from 2% to 12% when the ratio was 7/3, which was the best ratio.