CO2 electroreduction on Bismuth with Ionic Liquids

2 minute read


Electrochemical reduction of CO2 has attracted researchers’ attention as it has the potential to utilize the abundant greenhouse gas in the Earth’s atmosphere and store intermittent energy from solar panels and wind turbines in chemical bonds. Many metals show activities in reducing CO2 in aqueous phase. However, with the competition of the hydrogen evolution reaction, the selectivity is poor towards valued chemicals. Also, the high overpotential needed to drive the reactions causes low efficiencies that inhibits the practical applications.

CO2 cycle

Many metals show CO22 reduction activity

Current Knowledge and Focus

By using Bismuth (Bi) as catalysts and ionic liquids (ILs) as electrolytes under electrochemical conditions:

  • CO2 was reduced to CO instead of formate.
  • The CO2 reduction overpotential was reduced.
  • The selectivity was enhanced since the HER was compressed.

The underlying mechanism remains elusive due to the multi-step kinetics and the unclear interactions between ILs and key intermediates

CO2 Reduction in ILs

  • Exhibit an almost complete conversion of CO2 to CO (96.1 % FECO), and a mass activity for CO evolution (MACO) of 15.6 mA mg−1 at -2.0 V vs Ag/AgCl (~ 0.3 V overpotential).

Reaction Pathways of CO2 Reduction in ILs

Determining Energetics

  • Total reaction from CO2 to CO
  • Using thermodynamic cycle to determine reaction barriers

Modeling Solid-Electrolyte Interfaces

Calculation Details

  • VASP package
  • PBE functionals
  • 3 by 3 by 3 unit cell
  • Monkhorst-Pack mesh of 4 by 4 by 1
  • VASPsol hybrid solvation
  • Constant potential calculation

Electrostatic potential plot

  • Tuning the number of electrons in the system to change the Fermi level

Electrolyte-dependent Energy Pathways

  • Compared with aqueous phase condition, free formation energies of key intermediates are lowered in non-aqueous phase, and CO is produced.


  • Constant potential calculations can capture selectivity trends from aqueous phase and IL non-aqueous phase.
  • By employing ILs as co-catalysts on Bi surfaces, thermodynamic barriers are reduced since the stabilization of *CO2 and *COOH by hydrogen bonding, and CO is obtained as the final product.


Tianyou Mou

Tianyou Mou

Chemical Engineer and Data Scientist


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