Photoelectrochemical analysis of band gap modulated TiO2 for photocatalytic water splitting

Scheme depicting the mechanism of electron hole pair formation using TiO2-APTMS-FA for water splitting. The band gap energy Eg of TiO2 is 3.2 eV. Photons with energy larger than the HOMO/OV-LUMO gap (ħω1 > 2.0 eV) get absorbed by OV/APTMS/FA. Note that the HOMO state is hybridized with the OV band of TiO2 at the surface. The holes that are left behind in the HOMO/OV state are filled by e-h pair generation from the TiO2 valence band (VB) to the HOMO-OV state by photons (ħω2 > 2.5 eV). Regular e-h pair generation in the conduction band (CB) and VB takes place through absorption of photons with ħω3 > Eg. The green parts of the band bending represent the extra potential barrier coming due to the surface modifications.181