Homogeneous CO₂ Reduction by Ni(cyclam) at a Glassy Carbon Electrode

Abstract

The homogeneous CO(2) reduction activity of several nickel cyclam complexes was examined by cyclic voltammetry and controlled potential electrolysis. CO production with high efficiency from unsubstituted Ni(cyclam) was verified, while the activity was found to be attenuated with methyl substitution of the amines on the cyclam ring. Reactivity with CO(2) was also probed using density functional theory (DFT) calculations. The relative CO(2) binding energies to the Ni(I) state obtained from DFT were found to match well with the experimental results and shed light on the possible importance of the isomeric form of Ni(cyclam) in determining the catalytic activity.

Electrocatalytic Reduction of CO2by Copper (II) Cyclam Derivatives

“…2. In a N 2 -saturated condition, an irreversible reduction wave of Ni(II)/Ni(I) couple apprears at -1.22 V, which matches with prior studies reporting irreversible behaviors of Ni(II)/Ni(I) redox couple on a glassy carbon electrode in tri-HCl buffer and KCl solution [7,8]. Some other studies, however, reported quasi-reversible behaviors for the Ni(II)/ Ni(I) couple [5,6].…”

“…In a CO 2 -saturated solution, a large reduction current corresponding to electrocatalytic CO 2 reduction is observed. The onset potential of the CO 2 reduction is determined to be -1.18 V, which is consistent with prior studies [5][6][7][8].…”

“…Among the homogeneous electrocatalysts, Ni(II)-cyclam (cyclam: 1,4,8,11-tetrazazcyclotetradecane) and its derivatives have been known to exhibit remarkable efficiency and selectivity in converting CO 2 to CO [4][5][6][7][8][9]. It has been revealed that Ni(I)-cyclam, generated by one-electron-reduction of Ni(II)-cyclam, is the active catalytic species and the cyclam ligand stabilizes the Ni(I) state [5,7,10]. Ni(II)-cyclam, however, still exhibits rather high overpotential (ca.…”

“…-0.6 V), leading to the low energy efficiency for CO 2 conversion. In addition, Ni(II)-cyclam necessitates a mercury electrode to avoid hydrogen evolution and shows much less electrocatalytic activities on other environmentally-benign electrodes [5][6][7].…”

Organic reactions for the electrochemical and photochemical production of chemical fuels from CO2 – The reduction chemistry of carboxylic acids and derivatives as bent CO2 surrogates

“…A further example of CO-selective CO 2 -reduction molecular electrocatalyst is Ni(cyclam) 2+ [77,78]. Interestingly, Ni(cyclam) 2+ has also been shown to be an effective mediator for the electrosynthesis of cyclic carbonates (50) from epoxides (49) and CO 2 Eq.…”