Studies on the Behaviors of PbSO_4/Pb and PbO_2/PbSO_4 Electrodes Prepared from Lead Carbonate by Powder Microelectrode Technique

The behaviors ot PbSO4/Pb and PbO4/PbSO4 electrode prepared from PbCO3 have been examined using powder microelectrode(PME) technique and cyclic voltammetry(CV). Firstly, PMEs parked with Pb- CO3 transformed into PtSO4 PME in 1. 0 mol/L H2SO4 solution at 30 C, and then the PbSO4 in the PMEs were formed to Pb or PbO2 using an unsymmetrical signal(Qa/Qe for PbSO4/Pb electrode and Qe/Qa for PsO2/ PbSO4 electrode being 0. 1-0. 3) in 2. S mol/L H2SO4 solution. The results show that the CV characteristic of either PbSO4/Pb or PsO2/PbSO4 PME prepared from PhCO3 are as good as that of both electrodes made from lead oxide powder produced by ball mill.

Modification of Carbon Nanotube Powder Microelectrode and Nitrite Reduction

The properties of the carbon nanotube powder microelectrodes (denoted CNTPME) are remarkably altered by anodic pretreatment and preadsorption of mediators. It seems that anodic pretreatment leads the long and tangled carbon nanotubes to be partially cut shorter, resulting in more openings as shown by TEM. Besides, the anodic pretreatment may adjust the hydrophobicity of nanotubes to match with that of Os(bpy)32+. As a result, the real surface area and the ability of adsorbing mediator Os(bpy)32+ of the nanotubes are markedly increased so as to effectively catalyze NO2- reduction in acidic solution.

Decomposition mechanism of pentlandite during electrochemical bio-oxidation process

Electrochemical measurements were carried out to elucidate decomposition mechanism of pentlandite using modified powder microelectrode with Acidithiobacillus ferrooxidans attached or without on the mineral powder surface.Cyclic voltammetry（CV） results show that at a low potential of about-0.2 V（vs SCE）,the pentlandite was transformed to an intermediated phase like Fe4.5-yNi4.5-xS8-z when Fe and Ni ions were evacuated from mineral lattice;when the potential was changed from-0.2 V to 0.2 V,the unstable violarite（Fe3Ni3S4） and FeNi2S4 were formed which was accompanied by element sulfur formed on the mineral surface;when the potential increased over 0.2 V,the unstable intermediated phase decomposed entirely;at a higher potential of 0.7 V,the evacuated ferrous ion was oxidized to ferric ion.The presence of Acidithiobacillus ferrooxidans made the oxidation peak current increase with initial peak potential negatively moving,and the bacteria also contributed to the sulfur removing from mineral surface,which was demonstrated by the reduction characteristic at potential ranging from-0.75 to-0.5 V.Leaching experiments and electrochemical results show that the solution acidity increasing when pH2 may impede the oxidation process slightly.

A Special Property of DNA--as an Electrocatalyst

A new special property of DNA was found. It can remarkably catalyze the electrooxidation of catecholamine neurotransmitters. The electrocatalytic activity of DNA towards catecholamine neurotransmitters can be attributed to the interaction between DNA and the neurotransmitters.

Preparation and influence of performance of anodic catalysts for direct methanol fuel cell

This research aims at increasing the utilization of platinum-ruthenium alloy(Pt-Ru)catalysts and thus lowering the catalyst loading in anodes for methanol electrooxidation.The direct methanol fuel cell’s(DMFC)anodic catalysts,Pt-Ru/C,were prepared by chemical reduction with a reduc-ing agent added in two kinds of solutions under different circumstances.The reducing agent was added in hot solution with the protection of inert gases or just air,and in cold solu-tion with inert gases.The catalysts were treated at different temperatures.Their performance was tested by cyclic voltam-metry and potentiostatic polarization by utilizing their inher-ent powder microelectrode in 0.5 mol/L CH3OH and 0.5 mol/L H2SO4 solution.The structures and micro-surface images of the catalysts were determined and observed by X-ray diffrac-tion and transmission electron microscopy,respectively.The catalyst prepared in inert gases showed a better catalytic performance for methanol electrooxidation than that prepared in air.It resulted in a more homogeneous distribution of the Pt-Ru alloy in carbon.Its size is small,only about 4.5 nm.The catalytic performance is affected by the order of the reducing agent added.The performance of the catalyst pre-pared by adding the reductant at constant temperature of the solution is better than that prepared by adding it in the solu-tion at 0℃ and then heating it up to the reducing temperature.The structure of the catalyst was modified,and there was an increase in the conversion of ruthenium into the alloyed state and an increase in particle size with the ascension of heat treatment temperature.In addition,the stability of the catalyst was improved after heat treatment.