Electrochemical Studies At Room Temperature Ionic Liquid Of Choline Chloride/ Tartaric Acid

      The oxidation-reduction behavior of the newly prepared choline chloride/d-tartaric acid ionic liquid was studied by electrolysis at 25°C to 95°C with applied voltages of 0.5 to 5 volts. This ionic liquid was found stable up to 45°C and 5 volts as only showed small changes in current density. But, at 65°C the liquid showed noticeable unstable behavior particularly at or above 2.5 volt, which increased at higher temperature with increase conducting too. Solution of CuSO4.5H2O  showed similar behavior to ionic liquid alone but with increased current density and conductivity which was attributed to viscosity changes and presence of copper (II) ions. However, NiCl2 solution in ionic liquid decomposed at lower potential of  (1 volt) at 65°C while giving a similar behavior of current density and conductivity to copper solution. The CrO3 solution in ionic liquid was unstable from 65°C and 2.5 volts.  However the conductivity was found to be similar than in ionic liquid alone up to 50°C which increased  to more than ionic liquid at 60°C.  This was attributed to the reduction of Cr (VI) to Cr (ІІІ) as was   conformed by UV. Visible investigation  It was found possible to carry out electroplating of copper, nickel, and chrome from  their above solution at high potential and 85°C. The amount  of coated metals was found to increase with potential of 2, 2.5,and 3 volts.The non uniform irregular shapes of the coated metal particles were found to adhere strongly to the substrate of stainless steel,nickel, and copper. In addition the current efficiency was found to be high in case of chrome plating (~ 80%) while less than (50%) in copper and nickel plating                                          
    UV.Vis examination of CuSO4.5H2O indicate distorted octahedral  coordination in this ionic liquid while NiCl2 solution showed after electroplating process a mixed tetrahedral and octahedral spectra.
However CrO3 solution showed spectra of octahedral Cr (ІІІ) oxidation state when cooled from 85°C of the plating process indicating the reduction of Cr (VI) at around 60°C  when its solution change color.
Racah parameter, 10Dq , Nephelauxetic factor,  and molar absorption were calculated to the  above solutions.