Controllable C─N Coupling Toward Efficient Urea Electrosynthesis via Spin State Modulation on Fe Catalysts.

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Urea synthesis via CO2 and nitrate co-electrolysis is promising but faces challenges in intermediate reactivity and C-N coupling.
• Controlling these processes is crucial for enhancing catalytic performance and selectivity.

Purpose of the Study:

• To develop a strategy for regulating C-N coupling modes on Fe sites through spin state modulation for improved urea synthesis.
• To investigate the role of Cu doping in Fe3O4 catalysts for co-electrolysis of CO2 and nitrate.

Main Methods:

• Experimental synthesis and characterization of Cu-doped Fe3O4 catalysts.
• Electrochemical co-electrolysis experiments to evaluate urea synthesis performance.
• Density Functional Theory (DFT) calculations to elucidate reaction mechanisms and intermediates.

Main Results:

• Cu-doped Fe3O4 significantly promoted C-N coupling via the *CO + *NO2 → *CONO2 pathway.
• Achieved a urea Faradaic efficiency of 47.3% and a yield rate of 635.9 µg h-1 mgcat.-1 at low overpotential.
• Demonstrated exceptional stability (>30 h) and high selectivity towards urea.

Conclusions:

• Cu doping modulates the Fe spin state, enhancing CO2 activation and *CO coverage.
• Optimized *NO2 adsorption and coverage facilitate the key C-N coupling step and inhibit side reactions.
• The Cu-doped Fe3O4 catalyst offers a highly efficient and stable pathway for sustainable urea synthesis.