Zeolitic Intermetallics: LnNiSi (Ln = La-Nd)

Area of Science:

• Materials Science
• Solid-State Chemistry
• Catalysis

Background:

• Intermetallic compounds LnNiSi (Ln = La-Nd) feature a 3D NiSi framework with electrons in crystallographic cavities.
• These materials exhibit metallic electrical and magnetic properties due to low work functions.

Purpose of the Study:

• To investigate the hydrogen insertion properties of LnNiSi compounds.
• To evaluate the catalytic activity of Ru-loaded LaNiSi for ammonia synthesis.

Main Methods:

• Topotactic hydrogen insertion/de-insertion experiments within the 473-773 K temperature range.
• Characterization of structural and electronic changes during hydrogen interaction.
• Assessment of Ru-loaded LaNiSi as a catalyst for ammonia synthesis under ambient pressure.

Main Results:

• LnNiSi compounds reversibly absorb and desorb hydrogen without unit cell volume change between 473-773 K.
• Hydrogen insertion involves redox reactions with the orbitals of cavity-wall atoms.
• Ru-loaded LaNiSi demonstrates high catalytic efficiency for ammonia synthesis due to electron-donating power and hydrogen-electron exchange.

Conclusions:

• LnNiSi compounds are promising hydrogen storage materials with unique electronic properties.
• The electron-rich nature and reversible hydrogen interaction make Ru-LaNiSi an effective ambient-pressure catalyst for ammonia synthesis.