Actinide-uranium single-atom catalysis for electrochemical nitrogen fixation

Area of Science:

• Catalysis
• Materials Science
• Electrochemistry

Background:

• Actinide catalysts, particularly those with uranium (U), show promise for nitrogen (N2) fixation due to their unique 5f orbitals and variable oxidation states.
• Developing efficient and selective catalysts for N2 electroreduction is crucial for sustainable ammonia synthesis.

Purpose of the Study:

• To report the first successful dispersion of uranium single atoms on TiO2 nanosheets for N2 electroreduction.
• To investigate the catalytic performance and mechanism of single-atom uranium catalysts for ammonia synthesis.

Main Methods:

• Fabrication of single-atom uranium catalysts on TiO2 nanosheets using oxygen vacancy confinement.
• Electrochemical testing for N2 electroreduction, including yield and Faraday efficiency measurements.
• Operando synchrotron infrared spectroscopy and X-ray absorption spectroscopy to study reaction intermediates and metal-support interactions.
• Theoretical simulations to elucidate the catalytic mechanism.

Main Results:

• The single-atom U/TiO2 catalyst achieved a high NH3 yield of 40.57 μg h⁻¹ mg⁻¹ and a Faraday efficiency of 25.77%.
• Operando spectroscopy confirmed that the N2H y intermediate originated from the feed N2 gas.
• Enhanced U-TiO2 metal-support interaction with increased U-O lattice coordination was observed under working conditions.
• Theoretical calculations revealed that 1Oads-U-4Olatt moieties facilitate N2 dissociation and hydrogenation by lowering energy barriers.

Conclusions:

• Single-atom uranium dispersed on TiO2 nanosheets is a highly effective catalyst for N2 electroreduction.
• The catalyst's performance is attributed to strong metal-support interactions and the unique electronic properties of uranium.
• This work demonstrates a viable strategy for designing advanced actinide-based single-atom catalysts for nitrogen fixation.