Formation of Sol-Gel-Derived TaOxNy Photocatalysts

Tantalum oxynitride (TaON) is a visible photocatalyst (lambda < 520 nm) that has been investigated for green energy applications, specifically, the solar production of hydrogen gas. Metal oxynitrides are often generated by the ammonolysis of metal oxides at very high temperatures. We have investigated an alternative synthetic procedure to produce gram-scale quantities of photocatalytically active TaOxNy materials using room-temperature sol-gel chemistry. X-ray photoelectron spectroscopy (X.PS) results confirm that nitrogen was incorporated into materials with a Ta2O5 crystal structure. Optical characterization reveals that sol-gel-synthesized TaOxNy has a 2.3 eV bandgap, in agreement with bulk TaON. Furthermore, photoluminescence experiments reveal that two distinct material systems are being created during the initial sol phase of the synthesis: one species is primarily metal oxide, while the other is a N-doped species. This observation may lead to synthetic methods that improve the doping content of sol-gel-derived materials.