THE EFFECT OF CURRENT AND NICKEL NITRATE CONCENTRATION ON THE DEPOSITION OF NICKEL-HYDROXIDE FILMS

An electrochemical quartz crystal nanobalance (EQCN) has been utilized to measure the mass of Ni(OH)(2) films electrochemically deposited from Ni(NO3)(2) solutions. The objective of this work was to quantify electrochemical deposition as a function of deposition conditions. The changing mass recorded on the EQCN was demonstrated to be the result of Ni(OH)(2) deposition. Deposited mass was observed to increase proportionally with applied charge as suggested by previous investigators. Most significantly, the rate of deposition was found to decrease more than an order of magnitude as the Ni(NO3)(2) concentration increased from 0.2 to 2.0M. The effect of concentration is shown to be related to Ni(II) concentration as opposed to solution pH or NO3- concentration. An empirical correlation is given to predict deposition rates in solutions ranging from 0.1 to 3.0M Ni(NO3)(2) and at current densities ranging from 0.5 to 5.0 mA/cm(2). The decreased deposition rates in concentrated Ni(NO3)(2) are attributed to the formation of intermediate species [e.g., NiOH+ or Ni4(OH)(4)(4+)] which diffuse away from the reaction interface before deposition can occur.