Eleectrodeposiotion of Cu-In, PdCu, PdSn alloys from 1-ethyl-3-methylimidazolium Chloride tetrafluoroborate ionic liquid

• Main Authors: Li-HsienChou, 周麗嫺
• Other Authors: I-Wen Sun
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/61906202199798863436

博士 === 國立成功大學 === 化學系碩博士班 === 99 === The dissertation includes two parts : (1) Electrodeposition of Cu-In alloy and Se element in 1-ethyl-3-methylimidazolium Chloride tetrafluoroborate ionic liquid (EMI-Cl-BF4) on Induim Tin Oxide glass Electrodes (ITO) and (2) Electrodepostion of Pd-base alloy in 1-ethyl-3-methylimidazolium Chloride tetrafluoroborate ionic liquid (EMI-Cl-BF4) for Ehtnaol electro-oxidation. Fristly, in this study, the EMI-Cl-BF4 was as electrodeposite solution for electrodeposition of Cu-In alloy and Se element. As has been mentioned, the redox potential of Cu(I)/Cu couple (-0.05 V vs. Ag/AgCl) and In(III)/In couple (-0.8 V vs. Ag/AgCl) in aqueous solutions are very different, but in EMI-Cl-BF4 ionic liquid, their reduciotn potential are so close that codeposited Cu-In alloy easily. For these results, the composition of Cu-In alloy is charged by the concentration ratios of Cu(II) and In(III) in EMI-Cl-BF4 ionic liquid. When the concentration of Cu(II) is much more, the reduction potential of In(III) is shifted the more negative and hard to reach the same ratio content for Cu-In alloy. On the other hand, the concentario of In(III) is more than Cu(II), it is easy to obtain the same ratio composition of Cu-In alloy. Samples of Cu-In electrodeposits were prepared with potentiostatic electrolysis and characterized with SEM, EDS and XRD techniques. The composition of the Cu-In electrodeposits is almost independent on the deposition potential except for in the more negative potential. Electrodeposition of the selenium film in 1-ethyl-3-methylimidazolium chloride-tetrafluoroborate ionic liquid containing excess chloride ions on indium tin oxide (ITO) coated glass electrodes was studied at 30oC. Cyclic voltammogrammetric results indicate that the reduction reaction of Se(IV) to Se(0) is not a simple four-electron reduction. Scanning electron microscopy reveals that the morphology of the selenium deposits is affected by the applied deposition potential and X-ray powder diffraction data indicates the Se deposits is the crystalline of t-Se phase. Secondly, the electrodeposition of palladium-copper alloys in 1-ethyl-3-methylimidazolium chloride–tetrafluoroborate ionic liquid containing excess chloride ions was studied on indium tin oxide (ITO) coated glass electrodes at 120°C. Cyclic voltammogrammetric results indicate that the thermodynamic deposition potential of copper is more negative than that of palladium. The presence of palladium(II) reduces the overpotential required for the deposition of copper. In addition, underpotential deposition of copper on the palladium electrode was observed. In contrast, the presence of copper(II) increases the overpotential required for the deposition of palladium. Palladium–copper coatings were prepared on the ITO electrode by constant potential electrolysis. Scanning electron microscopy results indicate that the deposits had nodular morphologies. Calculations from X-ray powder diffraction data show that the crystal size of the deposit decreased with increasing deposition overpotential. The prepared palladium–copper coatings adhered well on the ITO substrates and showed a good electrocatalytic capability for the electro-oxidation of ethanol in alkaline solution. Electrodeposition of palladium–tin alloys from 1-ethyl-3-ethylimidazolium chloride–tetrafluoroborate ionic liquid was studied at 120°C. Sn(II) chloride reacts spontaneously with Pd(II) chloride, producing Sn(IV) and Pd nanoparticles. Solutions containing Sn(IV) and Pd(II) were used for potentiostatic electrodeposition of Pd–Sn. The composition of the Pd–Sn electrodeposits varied with the solution composition and deposition potential. Different alloy phases were observed with X-ray diffraction measurements. Whereas the Pd-rich Pd–Sn solid solution deposits are composed of compact nodules, the Sn-rich intermetallic Pd–Sn deposits are composed of polyhedral crystals of various phases. Compared to Pd-coated electrodes, Pd–Sn solid-solution-coated electrodes show enhanced ethanol electro-oxidation efficiency and stability in alkaline aqueous solutions. As Sn content increased, new Pd/Sn intermetallic phases formed, resulting in reduced catalytic efficiency for ethanol oxidation.