Advanced titanium dioxide fluidizable nanowire photocatalysts

Abstract

In photocatalytic water splitting, fluidization is known to minimize the adverse effects of mass-transfer, poor radiation distribution, parasitic back-reactions and photocatalyst handling difficulties, which limit the scalability of immobilized-film and suspended slurry photocatalysts. Fluidization of one-dimensional TiO₂ photocatalyst particles, such as nanorods, -wires and -ribbons, is highly desired as it further enhances the efficiency of photocatalytic reaction, due to their peculiar photo-electrochemical characteristics that result in more effective separation of photo-generated charges and absorption of photons. However, the harsh physical environment of a fluidized bed reactor does not readily allow for nanostructured TiO₂ photocatalysts, as the fine features would be quickly removed from the particle surface. Here, we propose a scalable method for fabrication of rutile TiO₂ nanorods on porous glass beads as a 3D protective substrate to reduce the attrition rate caused by fluidization. The quality of the synthesized nanorod films was optimized through controlling a growth quality factor, R_q, allowing for good quality films to be grown in different batch amounts and different hydrothermal reactor sizes. The utilization of porous glass beads substrate has reduced the attrition rate, and the protective features of the particles reduced the rate of attrition by an order of magnitude, compared to a particulate photocatalyst, to near negligible levels. Such considerably reduced attrition makes the as-developed porous glass beads supported rutile TiO₂ nanorods a viable fluidizable photocatalyst candidate for various applications, including water splitting and degradation of organic compounds.