Photopotential decay delay on TiO₂ surface modified with p‐benzaldehydes: consequences and applications

TiO 2 (Anatase) surface has been modified with p ‐substituted benzaldehydes ( p = OCH 3 , CH 3 , H, CN, and NO 2 ) and 4‐stilbene carboxaldehyde. Fourier transform infrared spectroscopy attenuated total reflectance spectroscopy, UV–Vis reflectance spectra, and theoretical calculations indicate that the TiO 2 surface has been chemically modified and supported acetal formation by means of TiO 2 –OH reaction with the aldehyde. A steady state photocurrent was obtained during simulated UV light irradiation of the acetal‐TiO 2 in aqueous solution. Once the light irradiation is turned off, open‐circuit potential decay measurements were used in order to determine the electron life‐time ( t n ). Excited electron decay is inhibited down to 1 s when the electron withdrawing delocalization capacity of the modified TiO 2 increases. Electron life‐time also depends on the solution reduction capacity. However, the unmodified TiO 2 life‐time does not. The TiO 2 modification results in a new series of photocatalysts that improve the organic contaminants degradation in solution because slow electron decay also induces retardation of the electron‐hole recombination. Therefore, there is a linear relationship between the electron decay life‐time and degradation rate constant. However, when electron delocalization is further increased in a way that the electron life‐time becomes ca. 7 s, degradation rate is kept constant. Therefore, the extra electron stability compromise degradation in such a way that the modified nanoparticle switches from a useful oxidant agent to a material that favors the charge carriers separation through a stable radical anion formation.