Nonprecious Single Atom Catalyst for Methane Pyrolysis.

Area of Science:

• Materials Science
• Chemical Engineering
• Catalysis

Background:

• Methane pyrolysis is a promising route for hydrogen and carbon production.
• Catalyst stability, particularly resistance to sintering and coke formation, is crucial for efficient methane pyrolysis.
• Understanding C-H bond activation mechanisms on catalyst surfaces is key to designing effective catalysts.

Purpose of the Study:

• To investigate the C-H bond activation and reaction pathways of methane pyrolysis on single nickel atoms and nickel clusters supported by titanium nitride (TiN) plasmonic nanoparticles.
• To evaluate the stability of these catalytic systems against sintering and coke formation.
• To compare the performance of single-atom nickel catalysts versus nickel clusters on TiN.

Main Methods:

• Ab initio spin-polarized density functional theory (DFT) calculations were employed.
• The complete reaction pathway for methane pyrolysis was modeled.
• Energy barriers for C-H bond activation and adsorption energies were calculated.

Main Results:

• Low C-H bond activation energy barriers were observed for both single nickel atoms (~1.10 eV) and nickel clusters (~0.88 eV) on TiN.
• Single-atom Ni-TiN exhibited weaker adsorbate binding and an endothermic reaction pathway, suggesting resistance to coke formation.
• Nickel clusters demonstrated a facile reaction pathway but were prone to coke formation due to a highly exothermic process.

Conclusions:

• Single-atom nickel catalysts on TiN offer potential for coke-resistant methane pyrolysis.
• However, the tendency of single-atom catalysts to sinter into clusters presents a challenge for long-term stability.
• Further research is needed to optimize catalyst design for both high activity and stability in methane pyrolysis.