This work was mainly focused on the investigation of thermal treatment impact of the mesoporous-assembled Ta2O5 nanoparticles synthesized via a facile sol-gel method with the aid of a mesopore-directing surfactant on their photocatalytic hydrogen production activity from a methanol aqueous solution under UV light irradiation. The synthesized Ta2O5 nanoparticles were characterized by X-ray diffraction, N-2 adsorption-desorption analysis, elemental carbon analysis, UV-vis absorbance spectroscopy, scanning electron microscopy, transmission electron microscopy, and selected-area electron diffraction. The experimental results strongly supported that the calcination temperature in the range of 500-800 degrees C significantly affected the physicochemical properties and hydrogen production activity of the synthesized Ta2O5 nanoparticles. The synthesized Ta2O5 nanoparticles exhibited the amorphous-to-crystalline phase transformation at the calcination temperature of 650 degrees C, at and beyond which the hydrogen production activity improvement was clearly observed. The most photocatalytically active and thermally stable Ta2O5 nanoparticle was obtained at the optimum calcination temperature of 700 degrees C, and its hydrogen production activity was captivatingly found to be higher than that of the commercial Ta2O5 and P-25 TiO2 powders. In addition, the optimized Ta2O5 nanoparticle exhibited a very good durability for multiple reuses without significant activity loss. (C) 2013 Elsevier B.V. All rights reserved.