Influence of <i>p</i>H<i> </i>and supporting electrolyte on electrochemical reduction of CO₂ using nickel(II) macrocyclic complex of 1, 3, 6, 9, 11, 14 - hexaazacyclohexadecane as catalyst at HMDE

Abstract

472-477Electrochemical studies on the title compound using cyclic voltammogram (CV) and control potential electrolysis (CPE) techniques reveal that it reduces CO2 electrocatalytically at -1.36V /SCE at hanging mercury drop electrode (HMDE) in aqueous medium using LiClO4 as a supporting electrolyte. The products are found to be CO and H2 in 3:2 mole ratio in the gaseous phase as detected using gas chromatography (GC) and trace amounts of formic acid in solution phase as detected using colorimetric technique. The Ik / Id values (where Ik is the kinetic current measured in the presence of CO2 and Id is the diffusion current measured in N2 atmosphere) observed at various pH values show that pH 5.0 is best suited for CO2 reduction. In addition, the hydrophobicity/hydrophilicity near the electrode surface provided by the cation of the supporting salt and its influence on CO2 reduction is discussed