cs7b03274_si_001.pdf (2.81 MB)
CO2 Reduction Promoted by Imidazole Supported on a Phosphonium-Type Ionic-Liquid-Modified Au Electrode at a Low Overpotential
journal contribution
posted on 2018-01-24, 00:00 authored by Go Iijima, Tatsuya Kitagawa, Akira Katayama, Tomohiko Inomata, Hitoshi Yamaguchi, Kazunori Suzuki, Kazuki Hirata, Yoshimasa Hijikata, Miho Ito, Hideki MasudaThe catalytic conversion of CO2 to useful compounds
is of great importance from the viewpoint of global warming and development
of alternatives to fossil fuels. Electrochemical reduction of CO2 using aromatic N-heterocylic molecules is
a promising research area. We describe a high performance electrochemical
system for reducing CO2 to formate, methanol, and CO using
imidazole incorporated into a phosphonium-type ionic liquid-modified
Au electrode, imidazole@IL/Au, at a low onset-potential
of −0.32 V versus Ag/AgCl. This represents a significant improvement
relative to the onset-potential obtained using a conventional Au electrode
(−0.56 V). In the reduction carried out at −0.4 V, formate
is mainly generated and methanol and CO are also generated with high
efficiency at −0.6 ∼ −0.8 V. The generation of
methanol is confirmed by experiments using 13CO2 to generate 13CH3OH. To understand the reaction
behavior of CO2 reduction, we characterized the reactions
by conducting potential- and time-dependent in situ attenuated total
reflection surface-enhanced infrared absorption spectroscopy (SEIRAS)
measurements in D2O. During electrochemical CO2 reduction at −0.8 V, the C–O stretching band for CDOD
(or COD) increases and the CO stretching band for COOD increases
at −0.4 V. These findings indicate that CO2 reduction
intermediates, CDOD (or COD) and COOD, are formed, depending on the
reduction potential, to convert CO2 to methanol and formate,
respectively.