Bi@Sn Core-Shell Structure with Compressive Strain Boosts the Electroreduction of CO₂ into Formic Acid

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Formic acid (HCOOH) production via CO2 electroreduction is economically viable only at high selectivity (>90%) and current density (j > -200.0 mA cm-2).
• Developing efficient catalysts is crucial for advancing CO2 electroreduction technologies.

Purpose of the Study:

• To develop Bismuth-tin (Bi@Sn) core-shell nanoparticles (NPs) to improve the activity and selectivity of CO2 electroreduction to HCOOH.
• To evaluate the performance of Bi@Sn NPs in both H-cell and flow-cell systems.

Main Methods:

• Synthesis of Bi@Sn core-shell nanoparticles.
• Electrochemical characterization in an H-cell using 0.5 m KHCO3 electrolyte.
• Performance evaluation in a flow-cell system with 2.0 m KHCO3 electrolyte using chronopotentiometric measurements.
• Theoretical studies (DFT) to understand the catalytic mechanism.

Main Results:

• Bi@Sn NPs achieved a Faradaic efficiency for HCOOH (FEHCOOH) of 91% with a partial current density (jHCOOH) of -31.0 mA cm-2 at -1.1 V in an H-cell.
• In a flow-cell system, Bi@Sn NPs demonstrated an FEHCOOH of 92% and 56% energy efficiency at a steady-state current density (j) of -250.0 mA cm-2.
• Theoretical calculations revealed that compressive strain in the Sn shell reduces the energy barrier for HCOOH formation.

Conclusions:

• Bi@Sn core-shell nanoparticles are effective catalysts for CO2 electroreduction to HCOOH.
• The developed catalyst system shows promise for industrial applications due to high selectivity and efficiency at relevant current densities.
• The synergistic effect between Bi core and Sn shell, along with compressive strain, significantly enhances catalytic performance.