However, the absorbance should not be converted into reflectance or vice versa by eqn. (9) or eqn. (10) due to the significant change of bandgap energy. Also, photocatalysts with similar bandgap energies could behave differently. This shows that the photocatalytic behaviors depend not only on the bandgap value but also on the positions of the conduction band and valence band of materials, which DRS cannot determine. The next sections will explain these phenomena and discuss the band structure of photocatalysts.