Can Supported Reduced Vanadium Oxides form H₂ from CH₃OH? A Computational Gas-Phase Mechanistic Study

Area of Science:

• Computational Chemistry
• Catalysis Science
• Materials Science

Background:

• Methanol dehydrogenation is a key process for hydrogen production.
• Vanadium oxides supported on TiO2 are promising catalysts for this reaction.
• Understanding the reaction mechanism is crucial for catalyst optimization.

Purpose of the Study:

• To elucidate the mechanistic pathways of methanol dehydrogenation on vanadium oxide clusters.
• To compare the catalytic activity of reduced (V(III)) and oxidized (V(V)) vanadium species.
• To identify favorable adsorption sites and reaction intermediates.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• A gas-phase vanadium oxide cluster model representing VOx/TiO2 was utilized.
• Various reaction pathways and methanol adsorption configurations were explored.

Main Results:

• Methanol dissociative adsorption is kinetically and thermodynamically feasible on V-O-Ti and V═O sites.
• Hydride and methoxide intermediates were identified, with hydride species showing catalytic potential.
• Hydrogen and formaldehyde formation is more favorable on reduced V(III) sites compared to V(V) sites.

Conclusions:

• Reduced vanadium sites (V(III)) exhibit superior activity for methanol dehydrogenation.
• The study provides a comprehensive mechanistic understanding of the process.
• DFT results offer insights for designing efficient VOx/TiO2 catalysts.