A STUDY ON THE ELECTROCHEMICAL REDOX BEHAVIOR OF ELECTROCHEMICALLY PREPARED NICKEL HYDROXIDES USING EQCM

摘要

Electrochemical redox reactions of electrochemically precipitated thin films of nickel hydroxide have been studied by the electrogravimetric method using an electrochemical quartz crystal microbalance. Cyclic voltamassograms show that in alkaline solutions α-Ni(OH)_2 gains mass during its oxidation and loses mass during reduction. β-Ni(OH)_2 film, on the other hand, shows a mass change behavior completely opposite to that of α-Ni(OH)_2, losing mass during oxidation and gaining mass during reduction. Phase transformation from α-Ni(OH)_2 to β-Ni(OH)_2 is found to proceed with a formation of intermediate phases. The cyclic voltammograms taken during the phase transformation show that the intermediate phases behave as single phases. Cyclic voltamassograms taken simultaneously, however, show that the intermediate phases behave as a microscopic mixture of α-Ni(OH)_2 and β-Ni(OH)_2.