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He S.,Kunming University of Science and Technology | Xu R.,Kunming University of Science and Technology | Xu R.,State Key Laboratory of Complex Nonferrous Metal Resources Cleaning Utilization | Han S.,Kunming University of Science and Technology | And 2 more authors.
Journal of the Electrochemical Society | Year: 2016

An electrochemical investigation of NaOH concentration on electrosynthesis of lead dioxide in alkaline solutions was performed using rotating disk electrodes (RDE). The results show that Pb(II) does not modify the evolution of oxygen in alkaline solutions, and the reaction taking place at 0.84 VSHE is under the mixed control of ionic transport and charge transfer. The Koutechy-Levich equation was used to calculate the value of diffusion coefficient D and apparent heterogeneous rate constant k of the PbO2 electrodeposition process at 0.84 VSHE. The results indicate that NaOH has a negative influence on the diffusion of Pb(II) within a NaOH concentration range of 2.5 ∼ 4.5 M. In addition, NaOH has a positive influence on the apparent heterogeneous rate constant of Pb(II) oxidation reactions within a NaOH concentration range of 2.5 ∼ 3 M, but a negative influence within a NaOH concentration range of 3 ∼ 4.5 M. XRD and SEM were employed to investigate the effects of NaOH concentration on phase composition and surface microstructures of deposits. The results show that PbO2 synthesized in an alkaline solution consists of pure α phase. The deposits are all composed of rounded nanocrystallites, except for the deposit synthesized in a solution of 3 M NaOH, which exhibited rod-like crystallite. © 2016 The Electrochemical Society.


He S.,Kunming University of Science and Technology | He S.,State Key Laboratory of Complex Nonferrous Metal Resources Cleaning Utilization | Xu R.,Kunming University of Science and Technology | Xu R.,State Key Laboratory of Complex Nonferrous Metal Resources Cleaning Utilization | And 3 more authors.
International Journal of Electrochemical Science | Year: 2016

An electrochemical investigation focused on electrosynthesis of lead dioxide in alkaline solutions, using rotating disk electrode (RDE) and rotating ring disk electrode (RRDE), has been carried out. The experiments show that Pb(II) haven't modified the evolution of oxygen in alkaline solutions, and the reaction taking place at 0.6 VSCE is under the mixed control of ionic transport and charge transfer. Koutechy-Levich equation has been used to calculate the value of diffusion coefficient D and apparent heterogeneous rate constant k of Pb(II) oxidation reaction at 0.6 VSCE. The calculation results indicate that Pb(II) itself has the negative influence on the diffusion of Pb(II). In addition, Pb(II) has the positive influence on the apparent heterogeneous rate constant of PbO2 electrodeposition process. The intermediate was discovered in PbO2 electrodeposition process using RRDE. XRD and SEM were employed to investigate the phase composition and surface microstructure of the synthesized deposit. The result confirms that PbO2 synthesized in an alkaline solution consists of pure α phase, but not all characteristic peaks are present and relative intensities are not in agreement with the ICDD card. The deposit shows the preferential orientation of growth in the (200) crystallographic plane, and the deposit is compact and uniform which is composed of rounded nanocrystallites. © 2016 The Authors.


Li F.Y.,Kunming University of Science and Technology | Xu C.Y.,Kunming University of Science and Technology | Xu C.Y.,State Key Laboratory of Complex Nonferrous Metal Resources Cleaning Utilization | Yang Y.Y.,Kunming University of Science and Technology | And 4 more authors.
Advanced Materials Research | Year: 2014

Carbon-coated nickel nanoparticles were synthesized by solvothermal method in l-buty-3-methylimidazolium tetrafluoraborate ionic liquid. The obtained products are characterized by X-ray powder diffraction (XRD), Raman spectroscopy, infrared spectroscopy and transmission electron microscopy (TEM). The magnetic properties of carbon-coated nickel nanoparticles have been investigated by vibrating sample magnetometry (VSM). It was found that the carbon-coated nickel nanoparticles showed excellent magnetic properties. The present route may give researchers more choices for preparing other carbon-coated transition metal nanoparticles. © (2014) Trans Tech Publications, Switzerland.


He S.,State Key Laboratory of Complex Nonferrous Metal Resources Cleaning Utilization | He S.,Kunming University of Science and Technology | Xu R.,State Key Laboratory of Complex Nonferrous Metal Resources Cleaning Utilization | Xu R.,Kunming University of Science and Technology | And 4 more authors.
Electrochemistry | Year: 2015

An α-PbO2 layer were synthesized on the Pb-0.3%(mass proportion)Ag alloy substrates by constant current electrosynthesis from an alkaline solution, and Pb-0.3%Ag/α-PbO 2 composite inert anode materials were obtained. An electrochemical investigation of α-PbO2 deposition process on the Pb-0.3%Ag alloy substrates, using anodic polarization technique, galvanostatic polarization technique and steady state polarization technique, has been carried out. The phase composition and surface microstructures of α-PbO2 layersindifferent synthesizing times were tested by means of XRD and SEM, respectively. The experimental data have shown that the process of α-PbO2 formationon Pb-0.3%Ag alloy substrates have several stages. The optimized conditions canbeeffectively improving the formation rate of α-PbO2 and avoid the occurrence of oxygen evolution reaction. The α-PbO2 deposition layer obtained in alkaline solution possesses compact structure, and it is composed of well developed spherical grains. © The Electrochemical Society of Japan, All rights reserved.


Yang Y.,Kunming University of Science and Technology | Xu C.,Kunming University of Science and Technology | Xu C.,State Key Laboratory of Complex Nonferrous Metal Resources Cleaning Utilization | Hua Y.,Kunming University of Science and Technology | And 5 more authors.
International Journal of Electrochemical Science | Year: 2015

The electrochemistry of Ni(II) was studied with voltammetry and chronoamperometry at glass carbon (GC), mild steel (MS) and Pt electrodes in 1-ethyl-3-methylimidazolium (EMIC) ionic liquid with ethylene glycol. Cyclic voltammetry results shows that Ni(II) could be reduced to nickel metal via a single-step electron transfer process. However, the anodic dissolution of the nickel deposits was sluggish. In addition, the initial reduction potential of Ni(II) shifted positively as the temperature or concentration of Ni(II) increased. The diffusion coefficient of Ni(II) was estimated to be 4.6×10-7 cm2 s-1. The average activation energy for diffusion coefficient is about 21.75 kJ/mol. The electrodeposition of nickel proceeds via three-dimensional instantaneous nucleation with diffusion-controlled growth on both glassy carbon and Pt substrates. Smooth and dense Ni deposits can be obtained from EMIC ionic liquid with glycol. © 2015 The Authors.

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