Ni Single-Atom Modulation of Ti-O Covalency Boosts Ammonia Oxidation Electrocatalysis.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Non-noble transition metal oxides, like TiO2, are promising for electrochemical ammonia oxidation (AOR) due to cost and stability.
• Challenges include low activity and poor selectivity towards N2, caused by limited active sites and high intermediate coupling barriers.

Purpose of the Study:

• To enhance TiO2-based catalysts for AOR using a Ni single-atom-induced covalent modulation strategy.
• To create Ni SAC@TiO2 with tunable Ti-O covalency for improved performance and N2 selectivity.

Main Methods:

• Synthesized Ni single-atom catalyst on TiO2 (Ni SAC@TiO2).
• Utilized X-ray absorption (XAS) and photoelectron spectroscopy (XPS) to characterize metal-support interactions and Ti-O covalency.
• Employed in situ SERS and ATR-SEIRAS to study reaction mechanisms and intermediate behavior.

Main Results:

• Ni SAC@TiO2 exhibited significantly enhanced Ti-O covalency and abundant active sites.
• Catalytic activity for AOR was nearly doubled compared to pristine TiO2.
• The catalyst demonstrated excellent stability, retaining >98% performance after 2000 cycles, and promoted selective N2 evolution.

Conclusions:

• Single-atom modulation of Ti-O covalency is an effective strategy for developing efficient and robust TiO2-based AOR catalysts.
• Ni SAC@TiO2 offers a promising, stable, and selective alternative to noble metal catalysts for electrochemical ammonia oxidation.