Surfactants Used in Colloidal Synthesis Modulate Ni Nanoparticle Surface Evolution for Selective CO₂ Hydrogenation

Area of Science:

• Materials Science
• Surface Chemistry
• Catalysis

Background:

• Colloidal chemistry enables uniform pre-catalyst preparation.
• Understanding atomic-level transitions to active surfaces is key for catalyst design.
• Challenges remain in elucidating in situ catalyst transformations.

Purpose of the Study:

• To investigate the surface evolution of colloidal Ni nanoparticles during CO2 hydrogenation.
• To elucidate the role of phosphine ligands in Ni nanoparticle surface modification.
• To understand the formation of active catalytic sites for CO2 hydrogenation.

Main Methods:

• Ambient-pressure X-ray photoelectron spectroscopy (AP-XPS).
• In situ environmental transmission electron microscopy (in situ E-TEM).
• Infrared spectroscopy and theoretical calculations.

Main Results:

• Phosphine-capped Ni nanoparticles show distinct surface evolution compared to amine-capped ones.
• Phosphorus diffusion at elevated temperatures forms Ni-P surfaces.
• Ni-P surfaces favor CO production, while metallic Ni favors CH4 production.
• Optimized P incorporation achieves unit selectivity for CO.

Conclusions:

• Surface modification via P incorporation is critical for selective CO2 hydrogenation.
• The Ni-P surface is a highly selective site for CO production.
• This work provides mechanistic insights for designing advanced hydrogenation catalysts.