Controlled Synthesis of a Vacancy-Defect Single-Atom Catalyst for Boosting CO₂ Electroreduction.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Single-atom catalysts (SACs) are crucial for efficient chemical transformations.
• Controlling defect sites in SACs can tune their catalytic activity.
• High-temperature synthesis offers pathways to engineer catalyst structures.

Purpose of the Study:

• To synthesize and characterize novel nickel-based single-atom catalysts.
• To investigate the effect of vacancy defects on catalytic performance for CO2 reduction.
• To explore the mechanism of defect formation during high-temperature synthesis.

Main Methods:

• High-temperature reactions of nickel precursors with nitrogen and oxygen sources.
• Synthesis of Ni-N3O and Ni-N4 single-atom catalysts.
• Electrochemical characterization including current density and Faradaic efficiency measurements.
• Density Functional Theory (DFT) calculations to understand defect effects.

Main Results:

• A vacancy-defect Ni-N3-V SAC was successfully synthesized at 800°C.
• The Ni-N3-V SAC exhibited a CO2 reduction current density of 65 mA cm⁻², with >90% Faradaic efficiency at -0.9 V vs. RHE.
• A record turnover frequency of 1.35×10⁵ h⁻¹ was achieved for CO2-to-CO conversion.
• The Ni-N4 SAC, lacking vacancy defects, showed significantly lower activity.

Conclusions:

• Vacancy defects in Ni-N3-V SACs dramatically boost electrocatalytic CO2 reduction.
• The Ni-N3-V SAC is a highly promising electrocatalyst for CO2-to-CO conversion.
• Understanding defect formation is key to designing advanced SACs.