Carbon Neutral Electrochemical Conversion Of Carbon Dioxide Mediated By [Mn+(Cyclam)Cl-N] (M = Ni2+ And Co3+) On Mercury Free Electrodes And Ionic Liquids As Reaction Media

In this work, the electrochemical reduction of carbon dioxide using [Mn+(cyclam) Cl-n] (M= Ni2+ and Co3+) 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 BMImBF4 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 CO2 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)].