Highly Selective Conversion of Carbon Dioxide to Methane by Copper Single Atom Electrocatalysts

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis
• Environmental Science

Background:

• Electrocatalytic carbon dioxide reduction (CO2RR) is crucial for addressing the greenhouse effect and energy crisis.
• Efficient catalysts are needed to overcome the slow kinetics of the eight-electron transfer required for high-value chemical production.
• Single-atom catalysts (SACs) offer high activity and selectivity, representing a frontier in heterogeneous catalysis.

Purpose of the Study:

• To develop an efficient catalyst for the highly selective electrocatalytic reduction of CO2 to methane (CH4).
• To investigate the performance and stability of copper single atoms loaded on a carbon substrate (Cu-NC).

Main Methods:

• Synthesis of a Cu-NC catalyst with atomic dispersed Cu-N3 sites.
• Electrocatalytic CO2 reduction experiments to determine Faradaic efficiency (FE) and product selectivity.
• Characterization using HAADF-STEM and XANES to confirm catalyst structure.
• Density functional theory (DFT) calculations to elucidate the reaction mechanism.

Main Results:

• The optimal Cu-NC-1-4 catalyst achieved a CH4 Faradaic efficiency (FE) over 50% in a wide potential window (-1.3 to -1.8 V vs. RHE).
• The highest FE for CH4 reached 67.22% at -1.6 V (vs. RHE), with CH4 selectivity among carbon products at 93.00%.
• The catalyst demonstrated negligible activity decay over a 70-hour stability test.
• DFT calculations confirmed that Cu-N3 sites effectively adsorb the *CO intermediate, promoting CH4 generation.

Conclusions:

• Cu-NC-1-4 is a highly selective and stable catalyst for electrocatalytic CO2 to CH4 conversion.
• The atomic dispersed Cu-N3 sites are key to the catalyst's high performance.
• This work provides a promising pathway for utilizing CO2 as a carbon source for valuable chemical production.