The electrochemical behavior of [Ni-II(Me-4-(NO(2)Bzo)(2)[14]tetraeneN(4))] (as a symmetric complex) and [Ni-II(Me-4-NO(2)Bzo[15]tetraeneN(4))] (as an unsymmetric complex) was studied at different electrode surfaces using cyclic voltammetry and chronoamperometry methods. The cyclic voltammograms of the complexes showed two one-electron irreversible oxidation processes (ligand-localized) as well as a one-electron quasi-reversible redox couple (metal-localized) at a more negative potential. The electropolymerization was performed by one-electron oxidation of the complexes at Pt and glassy carbon electrodes. The heterogeneous and homogeneous electrocatalytic activities of the complexes for CO2 reduction were also studied. In each case, both complexes exhibited excellent electrocatalytic activities for the reduction of carbon dioxide in an ACN solution. This was with an increase of the cathodic current and a diminution of the over-potential more than 600 mV, as compared to the processes at the absence of the complexes. The diffusion coefficients, D, of the complexes and the homogeneous electron transfer rate constants of the reaction between the electrochemically reduced nickel complex and CO2 were also determined using electrochemical methods. Finally, deactivation of complexes by follow-up reactions with CO2 was tested using cyclic voltammetric and electrolysis experiments. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.