F. Giannopoulos, N. Chronopoulou, E.A. Pavlatou, A. Karantonis
5th Regional Symposium on Electrochemistry South East Europe (2015), 7-11 June, Pravets, Bulgaria (poster)
In principle, nano-composite materials present superior properties than their simple counterparts. Such nano-composites can be fabricated by electrochemical cathodic codeposition. In the present work, the effect of hybrid multi-walled carbon nanotubes/Al2O3 particles (MWCNT/Al2O3) on the deposition of Ni from Watts solution is studied by Linear Sweep Voltammetry (LSV), Electrochemical Impedance Spectroscopy (EIS) and Scanning Electron Microscopy (SEM). Moreover, the fabrication of a MWCNT electrode is attempted by selective electrodeposition of the nanotubes. The presence of nanotubes enhances the current in comparison to the case of the pure Watts solution. The presence of SDS does not further increase the cathodic current. The increase of the cathodic current may be due to increase of the Ni electrodeposition rate or the increase of the proton reduction rate. The charged transfer resistance in the case of the Watts-MWCNT/Al2O3 bath is very small, indicating that Ni electrodeposition is catalyzed by the hybrid nanotubes. Similar conclusions are derived by comparing the LSVs with impedance spectra at various cathodic potentials. In order to achieve selective deposition of MWCNT on a graphite electrode, potentiostatic pulse electrodeposition/electrodissolution was performed. During the cathodic portion of the pulse, co-deposition of Ni and nanotubes was occurring whereas during the anodic portion of the pulse, Ni was dissolved from the composite matrix. This surface morphology is completely different than the morphology of a graphite electrode, indicating that MWCNT actually remained on the electrode surface. This modified electrode has very good capacitative properties, estimated around 9x10-4 F, for apparent area of 0.07 cm2. The capacitative properties of the electrode where evident during Cyclic Voltammetry in K4Fe(CN)6, where the redox peaks almost disappeared due to the high value of the capacitance current.