Titanium dioxide (TiO₂) is a semiconductor widely used for photocatalytic applications. Its most notable limitation is a wide optical bandgap (E_g~3.2 eV) that restrains its functionality to UV-irradiation (1). One way to solve this issue involves doping of TiO₂ with nitrogen and/or coupling with a narrow bandgap semiconductor, such as cadmium sulfide (CdS; E_g~2.42 eV). However, during the process of photocatalysis, CdS undergoes photocorrosion contaminating the water source (2). Common means of fixing this issue involve the use of hole scavengers, such as S^2- ions. In this work, we present a new alternative involving the use of a thin layer of poly(1,8-diaminocarbazole) (PDACz) as a protective agent against CdS photocorrosion. The hybrid system was fabricated by depositing N-TiO₂ on a fluorine doped tin oxide plate via sol-gel, CdS nanoparticles were deposited via SILAR method, and a thin PDACz film was deposited on the surface of the CdS nanoparticles. The prepared hybrid was characterized by x-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray spectroscopy. It was found that the cadmium/titanium ratio in the hybrid was 0.135 to 1. The N-TiO₂/CdS/PDACz hybrid system had a bandgap of 2.26 eV, as found via UV-vis spectroscopy. In studying the photodegradation of 4-chlorophenol, the reaction rate constant was 72% higher when applying the hybrid as catalyst compared to bare TiO₂. These findings indicate that the N-TiO₂/CdS/PDACz hybrid system may be a suitable option for future practical applications.

1. Chen, S. S. Mao, Chem. Rev., 107 (2) (2007) 2891-2959
2. Yamada, A. Y. Nosaka, Y. Nosaka, Journal of Electroanalytical Chemistry, 585 (1) (2005) 105-112