Study on Mechanisms on Metal Surface in Aqueous Solution by Electrochemical QCM Technique

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 08650868
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Metal making engineering
• Research Institution: Nagoya University
• Principal Investigator: OKIDO Masazumi Nagoya University, Center for integrated Research in Science and Engineering, Professor, 理工科学総合研究センター, 教授 (50126843)
• Co-Investigator(Kenkyū-buntansha): KURODA Kensuke Nagoya University, Graduate School of Engineering, Assistant Professor, 工学研究科, 助手 (00283408) ; ICHINO Ryoichi Nagoya University, Graduate School of Engineering, Associate Professor, 工学研究科, 講師 (70223104)
• Project Period (FY): 1996 – 1997
• Keywords: Electrochemical QCM / in situ observation / Reaction on Metal Surface / Porous Ni Electrode / Chalcogen / Au leaching / Cathode inhibitor

Research Abstract

Reaction mechanisms on the surface of metal electrode were investigated by electrochemical quarts crystal microbalance, EQCM,technique. The results consists of four parts as follows.
(1) The mass changes of Ni porous electrode prepared from Zn leaching of Ni-Zn alloy and standard Ni electrode were measured during cyclic voltammetry in pH 1 KOH solution. The values in potential and in current were different for both electrodes, but the shape of CV carve was similar. Mass gain was found on both electrodes with the increase of cycle number. Though, in porous Ni electrode, there was a mass gain-mass loss area in potential, that wasn't found in Ni electrode. This behavior would give the more active surface to the porous Ni electrode than Ni one.
(2) Reduction behavior of chalcogen in the formation of CuInX_2 (X=Se, Te) semiconductor compounds from acidic sulfate bath was investigated by electrodeposition method. Reduction behaviors of Se and Te proceeded in the similar mechanism, though the r eaction potential was different. After the reduction deposition in 0 valency as X simple element, X was continuously reduced until -2 valency, and following to the dissolution of deposits. During the electrodeposition of CuInX_2 (X=Se, Te) compound, X in alloy solved out as X^2-after Cu-X alloy deposited. In-X alloy formed after In^<3+> reacted with X^<2->, and finally, CuInX_2 compounds formed.
(3) As a new leaching method of the gold without using cyanidation process, the selective gold leaching method was investigated using the alkali solution with tiourea. As a result, it was found that leaching ability improved by adding sulfurous acid by EQCM technique. The effective potential existed to dissolve gold selectively and thiourea was oxidized when anode potential was too high.
(4) The adsorption and film formation behaviors of Zn^<2+> and PO_4^<3-> system as cathode inhibitor onto the metal surface was investigated to protect metals from corrosion by EQCM technique. The film thickness was dozens of nm from calculation of mass change by EQCM measurement, and it formed uniformly on the surface from AFM observation. There were two cases in adsorption and film formatin by the corrosion inhibitor under the cathodic polarization condition, one was gradual formation and the other was rapid formation.