Synthesis of hollow spherical tantalum oxide nanoparticles and their photocatalytic activity for hydrogen production

Nano-particles consisting of hollow spherical tantalum oxide (referred to as HSTaO in this work) were synthesized by using the nonionic triblock copolymer F127 as the structure-directing agent in an ethanol aqueous medium. The HSTaO had a large surface area (higher than 100 m2/g), and relatively uniform particle size, in the range of 50–200 nm. The wall thickness of the hollow spherical particles was measured to be about 15–17 nm and contained ultrafine Ta2O5 crystallites. The band gap of HSTaO (4.3 eV) is clearly wider than that of bulk Ta2O5 (3.9 eV), which can be attributed to the quantum size of the ultrafine Ta2O5 crystallites. In addition, HSTaO with core-shell Ni/NiO particles (co-catalyst) exhibited similar photocatalytic activity as bulk Ta2O5 with co-catalyst in hydrogen generation from methanol aqueous solution under photoirradiation, with the HSTaO photocatalyst showing higher stability than the bulk.