Electrodeposition of metal/hydeoxide nano-composite material

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The anomalous codeposition of Zn-Ni may be due to the preferential precipitation of zinc hydroxide on the cathode and the inhibition of nickel deposition according to the hydrogen production at the cathode and the pH increase. However, the author reports here that when both Zn^<2+> and Ni^<2+> coexist in the solution, the zinc hydroxide does not precipitate while the double hydroxide of both metals does.The formation of the double hydroxide and its electrolytic reduction at the cathode in zinc-nickel alloy deposition were investigated. By using an EQCM method combined with the electrochemical measurement, it was clarified that the hydrogen generation occurs prior to the alloy deposition and the double hydroxide adheres to the electrode surface. It was confirmed that the electrolytic reduction product of the adhered material on the quartz surface, was the zinc/nickel alloy with the Zn:Ni ratio of about 9:1, from the analysis by using SEM/EDX. It is considered that the double hydroxide adsorbed on the cathode surface acts as a precursor of the alloy deposition reaction.