Tailoring defect generation in SnO₂ nanostructures for increased selectivity in electrochemical CO₂ reduction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Achieving carbon neutrality requires efficient catalysts for carbon dioxide (CO₂) reduction.
• Existing catalysts often lack the required selectivity and industrial benchmark current densities.
• Developing facile synthesis methods for high-performance CO₂ reduction catalysts is crucial.

Purpose of the Study:

• To synthesize a mesoporous SnO₂ nanostructure catalyst via a facile soft-templating process.
• To enhance CO₂ reduction activity through defect engineering by low-temperature annealing.
• To investigate the catalytic performance and mechanism for electrochemical CO₂ reduction (ECO₂R).

Main Methods:

• Synthesis of mesoporous SnO₂ nanostructures using soft-templating.
• Defect engineering via annealing at an optimal temperature of 300 °C.
• Electrochemical characterization including cyclic voltammetry and chronoamperometry.
• Density Functional Theory (DFT) calculations to study reaction intermediates.
• Flow-cell testing with a gas diffusion electrode.

Main Results:

• The SnO₂-300V catalyst achieved 97.9% Faradaic efficiency (FE) for C1 products and 94.1% selectivity for formate (HCOO^-) at -1.1 V vs. RHE.
• A high partial current density of 12.6 mA cm^-2 for HCOO^- was observed, alongside high double-layer capacitance and low charge transfer resistance (R_CT).
• Flow-cell tests demonstrated a high current density of ~266 mA cm^-2 with FE_(HCOO^-) ≥ 90.0% in 1 M KOH, indicating industrial applicability.
• DFT calculations confirmed favorable adsorption energies for key intermediates, supporting enhanced ECO₂R activity.

Conclusions:

• Soft templating combined with defect engineering provides an effective strategy for designing high-performance CO₂ reduction catalysts.
• The optimized SnO₂-300V catalyst exhibits excellent selectivity, activity, and stability, meeting industrial requirements for CO₂ utilization.
• The study offers valuable insights into catalyst design for scalable electrochemical CO₂ reduction towards carbon neutrality.