Deep Eutectic Solvent-Mediated Interfacial Structuring Controls Dye Adsorption and Photocatalytic Kinetics at...

Area of Science:

• Materials Science
• Physical Chemistry
• Environmental Science

Background:

• Deep eutectic solvents (DES) are emerging as tunable media for chemical reactions.
• Titanium dioxide (TiO2) is a widely used photocatalyst, but its efficiency can be limited.
• Controlling interfacial organization is crucial for optimizing photocatalytic systems.

Purpose of the Study:

• To investigate DES as supramolecular regulators of solid-liquid interfaces in TiO2-based photocatalysis.
• To evaluate the impact of different DES formulations and immobilization strategies on dye adsorption and degradation.
• To elucidate the mechanisms behind DES-mediated photocatalytic enhancement.

Main Methods:

• Synthesis and characterization of TiO2 nanoparticles modified with various choline chloride-derived DES.
• Photocatalytic degradation experiments under visible light using methylene blue and methyl orange as model dyes.
• Kinetic analysis using the Langmuir-Hinshelwood model.
• Surface characterization using Surface Plasmon Resonance (SPR) and solution analysis using 1H NMR spectroscopy.

Main Results:

• DES significantly enhanced TiO2 photocatalytic activity, with rate constants increasing up to 17-fold.
• DES donors like ethylene glycol, glycerol, and malonic acid showed superior performance compared to TsOH and urea.
• Immobilized DES (TiO2-DES) generally offered lower or similar activity compared to physical mixtures (TiO2 + DES).
• SPR indicated weak, reversible DES-TiO2 interactions, ruling out permanent surface modification.
• 1H NMR confirmed DES disrupts dye π-π stacking, favoring monomeric species, with methylene blue showing greater enhancement than methyl orange.

Conclusions:

• DES act as effective supramolecular regulators, optimizing interfacial organization for enhanced TiO2 photocatalysis.
• The choice of hydrogen-bond donor in DES and the dye's molecular structure are critical factors for catalytic efficiency.
• DES-mediated enhancement primarily involves surface interactions and dye stabilization rather than permanent TiO2 modification.