Effect of molecular structure of the N, N′-bis(2-hydroxy-1-naphthaldehyde)-1,3-phenylenediimine ligand on the electrocatalytic properties of its Ni(II) complex for reduction of CO2

Abstract

The electrocatalytic activity of N, N′-bis(2-hydroxy-1-naphthaldehyde)-1,3-phenylenediimine, NMPD, and its Ni(II) complex in reduction of CO2 was studied in an N, N′–dimethylformamide, DMF, solvent by cyclic voltammetry and chronoamperometry methods. According to the cyclic voltammetry studies, the potential of CO2 reduction was −1.40 V and −1.18 V versus Ag/AgCl/KCl (sat'd) in the presence of the NMPD ligand and its Ni(II) complex respectively. In this way, the overpotential of CO2 reduction was reduced for about 700 mV and 920 mV in the presence of NMPD and its Ni(II) complex respectively. However, in the presence of NMPD, a higher increase was observed in the catalytic current of CO2 reduction with respect to the Ni(II) complex. By chronoamperometry, the homogeneous catalytic rate constant, k, for the electron transfer between the NMPD ligand and CO2 as well as the Ni(II) complex and CO2 was found to be 24.90 ± 0.98 M−1 s−1 and 0.71 ± 0.05 M−1 s−1 respectively. The diffusion coefficients, D, of the NMPD ligand and the Ni(II) complex in the DMF solvent were also determined as 9.8 × 10−6 cm2 s−1 and 8.9 × 10−6 cm2 s−1 respectively. Considering the results and also the molecular structure of the ligand, the electrocatalytic behavior of these compounds toward CO2 reduction are discussed in detail.