The visible-light driven photocatalytic destruction of NOx using mesoporous TiO2 spheres synthesized via a “water-controlled release process”

Abstract

Mesoporous anatase TiO₂ spheres with tunable sizes ranging from 400 nm to 3 μm were synthesized using an original so-called “water-controlled solvothemal release process”. In this method, the well-known esterification reaction between ethanol and acetic acid was creatively employed to generate water gradually during a solvothermal process. Thereafter, the slowly released water molecules functioned as nucleation centers for completing the hydrolysis of titanium tetraisopropoxide to produce homogenous mesoporous TiO₂ spheres. In reality, these samples consisted of densely packed nanoparticles that formed spherical secondary particles with interparticle pores. Research has demonstrated that the diameter of the TiO₂ spheres can be easily tuned by controlling the concentration of the Ti source in the starting solution. Regardless of their diameter, all of these TiO₂ spheres exhibited a high specific surface area (above 150 m² g⁻¹) originating largely from the contribution of mesopores. On the merits of their porous structure and related high specific surface area, the mesoporous TiO₂ spheres showed a higher photocatalytic activity than P25 for the oxidative photo-destruction of NO_x gas.