Identification of Sn₅ Active Site on SnO₂(110) for CO₂ Electroreduction via Constant-Potential Method and...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Tin oxide (SnO2) is widely used for electrocatalytic CO2 reduction (CO2ER) to formic acid (HCOOH).
• The precise active site and reaction mechanism on SnO2 surfaces remain debated.
• Existing studies often employ constant-charge methods, potentially misrepresenting surface behavior under operating potentials.

Purpose of the Study:

• To identify the specific active site for CO2ER on SnO2(110) surfaces.
• To elucidate the detailed reaction mechanism under electrocatalytic conditions.
• To understand the role of surface structure and potential in CO2 conversion efficiency.

Main Methods:

• Constant-potential density functional theory (DFT) calculations.
• Microkinetic simulations.
• Application of the Hard and Soft Acids and Bases (HSAB) principle.

Main Results:

• The Sn5 site on SnO2(110) was identified as the active site for CO2ER.
• A CO2_n (O-atom bound) mediated mechanism was revealed, differing from constant-charge method findings.
• Synergistic interactions between Sn5 and Sn4 sites enhance HCOOH production at negative potentials (<-1.2 V).
• Simulated results closely match experimental data for Faradaic efficiency and current density.

Conclusions:

• The constant-potential method is crucial for accurately determining active sites and mechanisms in CO2ER.
• The Sn5 site and O-bound CO2_n intermediate are key to efficient HCOOH formation on SnO2(110).
• Understanding these mechanisms provides insights for designing improved CO2 electrocatalysts.