M(II)Al₄ Type Layered Double Hydroxides-Preparation Using Mechanochemical Route, Structural Characterization and...

Area of Science:

• Materials Science
• Inorganic Chemistry
• Catalysis

Background:

• Layered double hydroxides (LDHs) are versatile materials with applications in catalysis.
• Optimizing synthesis routes is crucial for achieving phase-pure materials and enhanced properties.
• Copper-aluminum (CuAl) LDHs are of interest for catalytic applications.

Purpose of the Study:

• To optimize the synthesis of copper-poor and aluminum-rich layered double hydroxides (LDHs) of the CuAl4 type.
• To achieve phase-pure LDHs for the first time.
• To investigate the catalytic potential of synthesized LDHs in carbon monoxide oxidation.

Main Methods:

• Mechanochemical treatment of gibbsite to activate the starting reagent.
• Synthesis using copper nitrate and perchlorate salts to prevent side-product formation.
• Characterization using powder X-ray diffractometry, UV-Vis spectroscopy, FTIR, TGA, and SEM.
• Catalytic testing in CO oxidation with in situ DRIFTS.

Main Results:

• Phase-pure CuAl-LDHs were successfully synthesized for the first time.
• A selectivity series for cation incorporation was established: Ni2+ >> Cu2+ >> Zn2+ > Co2+ >> Mg2+.
• All synthesized solids exhibited catalytic activity in CO oxidation.
• A NiCoAl8 layered triple hydroxide demonstrated outstanding low-temperature oxidation and high CO conversion.

Conclusions:

• Mechanochemical activation and specific salt choices are key for synthesizing pure CuAl-LDHs.
• The established cation selectivity provides a guideline for designing new LDH materials.
• NiCoAl-based LDHs show significant promise as efficient catalysts for low-temperature CO oxidation.