Enhanced *COOH Adsorption over Edge-Rich Ni-N₄ Sites for Efficient Acidic CO₂ Electroreduction

Area of Science:

• Electrochemistry and Catalysis
• Materials Science
• Surface Chemistry

Background:

• Single-atom nickel (Ni) catalysts show promise for acidic CO2 reduction reaction (CO2RR) due to high CO selectivity.
• Performance limitations arise from weak interaction with *COOH intermediates at high current densities.
• Efficient CO2 conversion requires stronger intermediate binding for Ni-N4 sites.

Purpose of the Study:

• To enhance *COOH adsorption on isolated Ni-N4 sites via support vacancy engineering.
• To boost CO2RR activity and selectivity in acidic media using edge-rich Ni-N4 sites.
• To investigate the electronic structure modulation for improved single-atom catalyst performance.

Main Methods:

• Density Functional Theory (DFT) calculations for electronic structure and binding energy analysis.
• Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) for site characterization.
• X-ray adsorption spectroscopy (XAS) and in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) for validation.

Main Results:

• Edge-rich Ni-N4 sites were successfully introduced, confirmed by HAADF-STEM and XAS.
• DFT calculations showed an upward shift in Ni d-band center, strengthening *COOH binding.
• Optimized catalyst achieved >94.5% CO Faradaic efficiency at 800 mA cm-2 and 44.2% energy efficiency at pH 1.

Conclusions:

• Support vacancy engineering to create edge-rich Ni-N4 sites effectively enhances *COOH adsorption.
• This strategy significantly boosts activity and selectivity for acidic CO2RR at high current densities.
• Edge-site engineering offers a versatile pathway for optimizing single-atom catalysts for industrial applications.