Mechanism of Electrochemical Capture of CO2 via Redox Cycle of 2-Amino-3-chloro-1, 4-naphthoquinone in BMIMBF4

The mechanism of electrochemical capture of CO2 via redox cycle of 2-amino-3-chloro-1,4-naphthoquinone(ACNQ) in 1-butyl-3-methylimidazolium tetrafluoroborate(BMIMBF4) was investigated by cyclic voltammetry(CV) and in-situ Fourier transform infrared(FTIR) spectroelectrochemistry techniques. In the absence of CO2, ACNQ undergoes a reversible two-step one-electron process in BMIMBF4. The dianion (ACNQ(2-)) formed during electrochemical reduction can be used as nucleophiles to attack the eletrophilic carbon center of CO2 and form a stable CO2 adduct when CO2 is introduced. Furthermore, the stoichiometry of CO2 electrochemical capture was evaluated. The result indicates that 1 mol of ACNQ(2-) can capture 1 mol of CO2. Also, the possible structures of CO2 adducts in the reaction were calculated by the B3LYP method at the 6.311++G** level.