Doping high-surface-area mesoporous TiO₂ microspheres with carbonate for visible light hydrogen production

First-principles calculations suggest that doping TiO₂ with carbonate can effectively reduce the bandgap of TiO₂, thus making TiO₂ photoactive in the visible region of the solar spectrum. Herein we report a simple "one-pot" solvothermal method for synthesizing brown carbonate-doped TiO₂ microspheres. The diameter of the TiO ₂ microsphere is tunable from ∼0.5 to 4 μm with the nanopore size in the range of 3-11 nm. Remarkably, the specific surface area of these nanoporous anatase TiO₂ microspheres can be as high as 500 m ² g^-1. A controllable amount of carbonate could be incorporated into TiO₂ through low-temperature post-synthesis annealing, which extends the light absorption of the TiO₂ microspheres from the ultraviolet to the visible region of the solar spectrum. Very high photocatalytic activity of these carbonate-doped TiO₂ microspheres was demonstrated in the visible light region for both photocatalytic production of hydrogen from water and degradation of methyl orange. Under 3 Sun visible-light illumination (λ ≥ 400 nm), the carbonate-doped TiO₂ microspheres can produce 0.2 mmol H₂ h^-1 g^-1 of photocatalyst, which is significantly higher than those from various other TiO₂ photocatalysts. This journal is