Preparation of amorphous and nanocrystalline sodium tantalum oxide photocatalysts with porous matrix structure for overall water splitting

Herein, we report the preparation of a series of surfactant-free nanostructured sodium tantalum oxide using NaTa(OC₃H₇)₆ as a single precursor. The reaction conditions for the novel synthetic method were optimized and the morphology and crystal structure of the prepared materials were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Condensation and polymerization of NaTa(OC₃H₇)₆ under atmospheric pressure gave a porous amorphous structure that could be converted to crystalline NaTaO₃ while crystalline Na₂Ta₂O₆ nanocrystals with a 25nm average particle size could be obtained from a hydrothermal method using NH₃ as a base catalyst. In addition, the photocatalytic behaviors of the prepared materials were investigated for overall water splitting into hydrogen and oxygen. Unexpectedly, porous amorphous sodium tantalum oxide showed much better catalytic activity over the crystalline one. The synthesized Na₂Ta₂O₆ nanocrystals also indicated promising activity for overall water splitting without any co-catalyst in comparison to bulk NaTaO₃.