Efficient and Robust Carbon Dioxide Electroreduction Enabled by Atomically Dispersed Sn^{δ +} Sites

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrocatalytic carbon dioxide (CO2) reduction requires significantly low overpotentials, which remains a considerable challenge.
• Developing efficient electrocatalysts is crucial for accelerating CO2 reduction and mitigating environmental concerns.

Purpose of the Study:

• To design and fabricate a positively charged single-atom metal electrocatalyst to reduce overpotentials for CO2 electroreduction.
• To investigate the mechanism of CO2 activation and protonation on the designed electrocatalyst.
• To enhance the rate-limiting formate desorption step in the CO2 reduction process.

Main Methods:

• Fabrication of kilogram-scale single-atom Snδ+ on N-doped graphene using a freeze-vacuum drying-calcination method.
• Characterization using synchrotron-radiation X-ray absorption fine structure (XAFS) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).
• In situ Fourier transform infrared spectroscopy (FTIR) and Gibbs free energy calculations to affirm reaction mechanisms.

Main Results:

• Atomically dispersed, positively charged Sn atoms on N-doped graphene were successfully synthesized.
• The catalyst demonstrated spontaneous CO2 activation and protonation by stabilizing key intermediates (CO2•− and HCOO−).
• N-doping facilitated formate desorption, reducing desorption energy and increasing turnover frequency to 11930 h−1.
• A very low onset overpotential of 60 mV for formate production was achieved with sustained activity over 200 hours.

Conclusions:

• Positively charged single-atom electrocatalysts offer a new strategy for significantly reducing overpotentials in CO2 electroreduction.
• The developed single-atom Snδ+ on N-doped graphene catalyst exhibits exceptional activity and stability for formate production.
• This work provides a novel pathway for manipulating electrocatalytic performance through catalyst design.