Bandgap optimization of sol–gel-derived TiO2 and its effect on the photodegradation of formic acid

This work reports a key factor, the H2SO4 concentration, in controlling the physicochemical properties of titanium dioxide (TiO2) photocatalysts during the sol–gel synthesis. The photocatalysts synthesized using different concentrations of H2SO4 possess specific anatase/rutile ratios and crystallite sizes as well as surface areas, resulting in different photocatalytic performance in the degradation of formic acid in solution. The best photocatalytic performance is observed for the TiO2 photocatalyst containing a relatively high percentage of the rutile phase (∼84%), which is obtained from the sol–gel synthesis without H2SO4.