Chemical Design of Efficient Photoelectrodes by Heterogeneous Nucleation of Carbon Dots in Mesoporous Ordered Titania Films

The design of efficient and highly durable photoelectrodes requires innovative solutions that can be integrated into thin-film-based technologies. Mesoporous ordered titania, which is characterized by an organized porosity in the 2-10 nm range, represents an ideal matrix for such a purpose. One of the main challenges is the homogeneous and controlled incorporation of photoactive nanoparticles inside the matrix. Titania-carbon dots (C-dots) heterostructures represent promising candidates, but a method to homogeneously introduce C-dots in mesoporous films is still missing. In the present work, C-dots have been nucleated and grown within a mesoporous titania film through in situ solvothermal synthesis. The process promotes the crystallization of titania anatase at low temperatures and at the same time allows the formation of carbon dots without disruption of the porous ordered structure. The process allows building a high-performance nanocomposite as an electrode for oxygen evolution reactions. Photocurrent production under different illumination conditions was measured by linear sweep voltammetry and chronoamperometry. When exposed to a solar simulator, the nanocomposite electrodes yield an increase in photocurrent compared to bare TiO2 matrices. The better performance has been associated with the presence of C-dots acting as active light-harvesting sites and as charge donors to the photoactive centers of the titania film.