TiO₂-Mo₂C Heterostructure for Enhanced Electrocatalytic Nitrogen Reduction to Ammonia

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing efficient electrocatalysts for the nitrogen reduction reaction (NRR) is critical for sustainable ammonia synthesis.
• Molybdenum carbide (Mo2C) shows potential for NRR but suffers from poor N2 adsorption/activation and hydrogen evolution competition.
• Heterostructure catalysts offer a strategy to overcome limitations of single-component materials.

Purpose of the Study:

• To investigate the potential of TiO2-Mo2C heterostructures as electrocatalysts for the electrochemical nitrogen reduction reaction (NRR).
• To elucidate the mechanism of enhanced N2 adsorption and activation in the TiO2-Mo2C system.
• To provide theoretical guidance for designing advanced NRR electrocatalysts.

Main Methods:

• First-principles theoretical calculations were employed to study the electronic and catalytic properties of the TiO2-Mo2C heterostructure.
• Analysis of orbital interactions (Mo 4d and N2 2p*) and electronic structure (integrated crystal orbital Hamilton population) was performed.
• Thermodynamic calculations of Gibbs free energy for N2 adsorption versus hydrogen evolution were conducted.
• The catalytic mechanism for N2 reduction to NH3 was investigated, comparing associative distal and alternating pathways.

Main Results:

• The TiO2-Mo2C heterostructure demonstrates significantly enhanced N2 adsorption and activation compared to Mo2C alone.
• Increased interaction between Mo 4d and N2 2p* orbitals, facilitated by TiO2, is responsible for improved N2 activation.
• Theoretical calculations show a preference for N2 adsorption over hydrogen evolution.
• The associative distal pathway was identified as the dominant mechanism for N2 conversion to NH3 on the TiO2-Mo2C surface.

Conclusions:

• The TiO2-Mo2C heterostructure exhibits unique advantages for the electrochemical nitrogen reduction reaction.
• This heterostructure design effectively enhances N2 adsorption and activation, crucial for efficient NRR.
• The findings provide valuable theoretical insights for the development of next-generation NRR electrocatalysts.