Dynamic Reconstitution Between Copper Single Atoms and Clusters for Electrocatalytic Urea Synthesis

Area of Science:

• Electrochemistry and Catalysis
• Materials Science
• Sustainable Chemistry

Background:

• Electrocatalytic carbon-nitrogen coupling is crucial for carbon footprint reduction, waste valorization, and sustainable urea production.
• Identifying active sites and designing efficient electrocatalysts for this process remain significant challenges.

Purpose of the Study:

• To synthesize and characterize a novel electrocatalyst for urea production via carbon dioxide and nitrate coupling.
• To identify the active catalytic species and understand the reaction mechanism during electrocatalysis.

Main Methods:

• Synthesis of copper single atoms supported on cerium dioxide (Cu1-CeO2).
• Electrochemical characterization including urea yield rate measurements.
• In-situ/operando X-ray absorption spectroscopy (XAS) and Fourier transform infrared spectroscopy (FTIR).
• Theoretical calculations to validate reaction pathways.

Main Results:

• The Cu1-CeO2 catalyst achieved an average urea yield rate of 52.84 mmol h-1 gcat.-1 at -1.6 V.
• Operando XAS revealed the in-situ transformation of single copper atoms (Cu1) into copper clusters (Cu4) during electrolysis.
• Cu4 clusters were identified as the active sites for electrocatalytic urea synthesis, confirmed by operando FTIR and theoretical calculations.
• The catalyst demonstrated dynamic and reversible transformations between single-atom and cluster configurations, ensuring high structural and electrochemical stability.

Conclusions:

• Electrocatalytic urea synthesis from CO2 and nitrate is feasible using a Cu1-CeO2 catalyst.
• The active sites are dynamically formed Cu4 clusters, which reversibly transform from Cu1 single atoms under applied potential.
• This study provides insights into catalyst active site evolution and offers a promising strategy for stable and efficient electrocatalytic urea production.