Carbon neutral electrochemical conversion of carbon dioxide mediated by [Mn+(cyclam)Cln] (M = Ni2+ and Co3+) on mercury free electrodes and ionic liquids as reaction mediaElectronic supplementary information (ESI) available. See DOI: 10.1039/c6gc02599d

• Main Authors: Honores, J, Quezada, D, García, M, Calfumán, K, Muena, J. P, Aguirre, M. J, Arévalo, M. C, Isaacs, M
• Format: Article
• Language: English
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/c6gc02599d

In this work, the electrochemical reduction of carbon dioxide using [M n + (cyclam)Cl n ] (M = Ni 2+ and Co 3+ ) as electrocatalysts has been studied in 1-butyl-3-methylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMImBF 4 and BMImNTf 2 respectively) ionic liquids as reaction media. Complexes were characterized electrochemically in these salts and relevant parameters, such as a heterogeneous electron transfer rate was calculated. Results indicate a faster M( ii )/M( i ) redox process in BMImBF 4 despite its higher viscosity compared to BMImNTF 2 . Cyclic voltammetry experiments demonstrated that [Ni(cyclam)Cl 2 ] is the most active macrocycle, towards the reaction under survey. For this compound, potential controlled electrolysis was carried out at−1.4 V vs . Ag/AgCl in BMImBF 4 as a solvent, yielding only CO as a reaction product, with a turnover frequency (TOF) of 0.73 h −1 . NMR spectra for the ionic liquids, after electrolysis, show that the applied potential does not affect the chemical structure of the salts. FT-IR thin layer spectroelectrochemical experiments in CO 2 saturated solution in BMImBF 4 at −1.4 V vs . Ag/AgCl show the formation of [Ni(cyclam)CO] + as precursor species, and also the most stable [Ni(CO) 4 ]. Carbon dioxide is reduced to carbon monoxide with high faradaic efficiency on mercury free electrodes using M(cyclam) complexes.