Thermal-Treated α-Bi₂O₃ Electrocatalyst for Efficient CO₂ Electroreduction toward Formate.

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical CO₂ reduction (CO₂RR) offers a sustainable route for converting CO₂ into valuable products.
• Bismuth (Bi)-based electrocatalysts show promise for CO₂RR to formate (HCOO^-), but often suffer from structural instability.
• This instability leads to decreased activity and selectivity during the reaction.

Purpose of the Study:

• To develop a thermal treatment strategy for tuning the catalytic properties of α-Bi₂O₃ for enhanced CO₂RR.
• To investigate the structural and mechanistic factors responsible for improved performance in Bi-based electrocatalysts.
• To provide insights into the selective formation of formate (HCOO^-) via CO₂ reduction.

Main Methods:

• Synthesis of α-Bi₂O₃ electrocatalyst.
• Optimization of the electrocatalyst through controlled thermal treatment (Bi-400).
• Electrochemical characterization including Faradaic efficiency measurements and long-term stability tests.
• In-depth structural and mechanistic studies (e.g., XPS, in-situ/operando techniques).

Main Results:

• The thermally optimized Bi-400 electrocatalyst achieved a high Faradaic efficiency of 93.0% for HCOO^- production at -0.95 V vs RHE.
• The catalyst demonstrated excellent operational stability, maintaining performance over 70 hours.
• Preserved Bi-O motifs in Bi-400 were identified as crucial for facilitating CO₂ activation and optimizing the binding of the *OCHO intermediate.

Conclusions:

• Thermal treatment is an effective method to enhance the stability and performance of Bi-based electrocatalysts for CO₂RR.
• The optimized Bi-400 catalyst significantly improves activity and selectivity towards formate production.
• Understanding the role of preserved structural motifs provides a pathway for designing advanced electrocatalysts for CO₂ conversion.