CNT-TiO₂ core-shell structure: synthesis and photoelectrochemical characterization

Porous composite coatings, made of a carbon nanotube (CNT)-TiO₂ core-shell structure, were synthesized by the hybrid CVD-ALD process. The resulting TiO₂ shell features an anatase crystalline structure that covers uniformly the surface of the CNTs. These composite coatings were investigated as photoanodes for the photo-electrochemical (PEC) water splitting reaction. The CNT-TiO₂ core-shell configuration outperforms the bare TiO₂ films obtained using the same process regardless of the deposited anatase thickness. The improvement factor, exceeding 400% in photocurrent featuring a core-shell structure, was attributed to the enhancement of the interface area with the electrolyte and the electrons fast withdrawal. The estimation of the photo-electrochemically effective surface area reveals that the strong absorption properties of CNT severely limit the light penetration depth in the CNT-TiO₂ system.