(483e) Colloidal Synthesis of Tantalum (Oxy)Nitride Clusters

The development of water splitting
photocatalysts for hydrogen production is potentially an important component of
the complex strategy that will be required to meet our energy needs.

Tantalum (oxy)nitrides have been suggested by Domen et al. as novel
visible light-driven photocatalysts (lambda< 600nm)
for water splitting. Traditionally Ta₃N₅ and TaON are
synthesized as bulk powders through high temperature (1000 C) nitriding
processes using ammonia. Our strategy focuses on the low temperature (< 300 C) synthesis of colloidal Ta₃N₅
nanocrystals(NCs) and sol-gel derived TaO_xN_y. Our Ta₃N₅
NCs made by a colloidal synthesis method are highly crystalline with particle
sizes from 2 to 10 nm. However, these materials are air sensitive and easily
oxidized possibly during synthesis as opposed to post-situ oxidation. TaO_xN_y
was synthesized through a wet-chemical sol-gel route.

To complement our experiments, density functional theory calculations provide
some insight as to active sites and desired size range for photocatalytic NCs.
We have found that (100) and (110) surfaces are the most stable faces of Ta₃N₅.
We also examined the adsorption and dissociation of O₂ and H₂O
on these surfaces to understand the mechanism of oxidation of Ta₃N₅.