Catalytic Ammonia Synthesis over Pure, Defective, and Metal-Doped Rutile TiO₂: A Periodic DFT Study.

Area of Science:

• Materials Science
• Catalysis
• Surface Chemistry

Background:

• Ammonia synthesis is crucial for global food production.
• Rutile TiO2 (110) is a potential catalyst but requires modification for efficient ammonia formation.
• Hydroxylation of TiO2 surfaces creates active sites for N2 activation.

Purpose of the Study:

• To investigate the energetic effects of doping rutile TiO2 (110) surfaces with Mo and Ta on ammonia synthesis.
• To understand the role of dopant location (Ti6c vs. Ti5c sites) and concentration.
• To identify optimal doping strategies for improved catalytic performance.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Energetics of reaction intermediates for ammonia formation were analyzed.
• The influence of Mo and Ta dopants on hydroxylated TiO2 (110) surfaces was modeled.

Main Results:

• Mo and Ta doping significantly reduced the energy barriers of key intermediates in ammonia synthesis.
• Doping at the Ti6c site of the vacant O2c site showed a stronger energetic effect than doping at Ti5c sites.
• Increasing dopant concentration on the vacant site led to a more substantial decrease in intermediate energies.

Conclusions:

• Mo and Ta doping are effective strategies to enhance ammonia synthesis over rutile TiO2 (110).
• Optimizing dopant location and concentration, particularly at the Ti6c site, is crucial for maximizing catalytic efficiency.
• The findings suggest potential for developing improved catalysts for sustainable ammonia production.