In Situ Raman Study of the Photoinduced Behavior of Dye Molecules on TiO2(hkl) Single Crystal Surfaces

In dye-sensitized solar cells (DSSCs), the TiO2/dye interface significantly affects photovoltaic performance. However, the adsorption and photoinduced behavior of dye molecules on the TiO2 substrate remains unclear. Herein, shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) was used to study the adsorption and photoinduced behavior of dye (N719) molecules on different TiO2(hkl) surfaces. On TiO2(001) and TiO2(110) surfaces, in situ SHINERS and mass spectrometry results indicate S=C bond cleavage in the anchoring groups of adsorbed N719, whereas, negligible bond cleavage occurs on the TiO2(111) surface. Furthermore, DFT calculations shows the stability of the S=C anchoring group on three TiO2(hkl) surfaces in the order: TiO2(001) < TiO2(110) < TiO2(111), which correlated well with the observed photocatalytic activities. This work reveals the photoactivity of different TiO2(hkl) surface structures and can help with the rational design of DSSCs. Thus, this strategy can be applied to real-time probing of photoinduced processes on semiconductor single crystal surfaces.