Mild Synthesis of Ag-Decorated TiO₂ Aerogels for Light-Driven CO₂ Reduction

Area of Science:

• Materials Science
• Nanotechnology
• Catalysis

Background:

• Nanoparticle gelation is key for aerogel synthesis, requiring stable, concentrated dispersions.
• Traditional titanium dioxide (TiO2) dispersion methods use corrosive acids (e.g., HCl), limiting material compatibility and generating hazardous byproducts.
• Acidic conditions also pose challenges for co-dispersing other nanoparticles like silver (Ag), hindering the creation of advanced composite aerogels.

Purpose of the Study:

• To develop a novel, acid-free method for dispersing TiO2 nanoparticles using trisodium citrate.
• To enable nanoparticle gelation under a wider pH range, including near-neutral conditions.
• To synthesize and evaluate novel composite aerogels, specifically Ag/TiO2, for catalytic applications.

Main Methods:

• Functionalization of TiO2 nanoparticles with trisodium citrate to create stable colloids across a broad pH range (3-12).
• Synthesis of aerogels using a metal alkoxide precursor, avoiding TiCl4 and HCl byproduct.
• Demonstration of cogelation of Ag and TiO2 nanoparticles at near-neutral pH.

Main Results:

• A highly dispersed TiO2 colloid stable from pH 3 to 12 was achieved using trisodium citrate.
• TiO2 nanoparticle gelation was successful under previously inaccessible conditions (pH 4, 6.5, 9).
• Catalytically active and photothermally enhanced Ag/TiO2 aerogels were synthesized via a chloride-free, near-neutral pH route, showing promise for CO2 reduction.

Conclusions:

• The citrate-based, chloride-free method provides a versatile platform for TiO2 nanoparticle dispersion and aerogel fabrication.
• This approach overcomes limitations of acid-based methods, enabling the synthesis of diverse multicomponent aerogels.
• The developed Ag/TiO2 aerogels demonstrate significant potential for efficient (photo)catalysis in sustainable chemical processes like CO2 conversion.