Precatalyst Engineering Directs Reconstruction Into Coupled Defective Sites for Selective CO₂‑to‑Formate...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Bismuth-based materials show promise for CO2 electroreduction to formate.
• Controlling dynamic reconstruction of these materials to define active sites remains a challenge.

Purpose of the Study:

• To develop a precatalyst engineering strategy to control the reconstruction pathway of bismuth-based materials.
• To achieve targeted active sites for efficient CO2 electroreduction.

Main Methods:

• Utilized bismuth oxyiodide (BiOI) as a model system.
• Engineered precatalysts with different crystallographic structures (layered BiOI vs. non-stoichiometric Bi5O7I).
• Employed in situ characterization and theoretical calculations to elucidate evolution mechanisms.

Main Results:

• Layered BiOI transformed into metallic Bi, favoring hydrogen evolution.
• Non-stoichiometric Bi5O7I preserved iodine, reconstructing into a surface with bismuth vacancies and iodine dopants.
• Achieved 96.8% formate Faradaic efficiency at 400 mA cm-2 with Bi5O7I.
• Demonstrated stable operation for over 100 hours at 200 mA cm-2.

Conclusions:

• Crystallographic structure dictates the reconstruction pathway toward targeted active sites.
• The defective configuration in Bi5O7I is crucial for high-efficiency CO2 electroreduction.
• Established a design principle for bismuth oxyhalide precatalysts for programmed reconstruction.