Facile one-pot synthesis of uniform TiO₂-Ag hybrid hollow spheres with enhanced photocatalytic activity

TiO₂-Ag hybrid hollow spheres (about 700 nm in diameter) with a highly uniform morphology and good structural stability were facilely prepared via a one-pot hydrothermal method, using carbon spheres as templates followed by an annealing treatment. Through this route, the as-prepared hybrid hollow spheres preserved the uniformity of the initial carbon sphere templates and the loading amount of the Ag nanocrystals can be conveniently varied or controlled by the concentration of the Ag precursor. The investigation of the photocatalytic ability demonstrated that the as-prepared TiO₂-Ag hybrid hollow spheres possess excellent photocatalytic activity, superior to commercial TiO₂ nanoparticles (Degussa P25), for the degradation of rhodamine B (RhB) and methyl orange (MO) dyes under visible-light illumination. Furthermore, the OH radicals formed during photocatalysis with different Ag content hybrids were revealed by means of a terephthalic acid fluorescence probe method, which uncovers that the Ag content in the TiO₂-Ag hybrids was crucial to obtain an optimal synergistic effect between the Ag and TiO ₂ for the degradation of organic pollutants. Accordingly, the optimum matching for the best photocatalytic activity was investigated thoroughly and a reasonable mechanism was also proposed.