In this study, free-standing and well-aligned titanium dioxide (TiO2) nanowires were grown on a Ti foil by precisely controlling the growth temperature and the thickness of the Ge catalyst layer. The catalyst layer played an important role in activating the surface of the Ti foil, facilitating the growth of TiO2 nanowires on it in a chemical vapor deposition furnace system. The structure of the TiO2 nanowires was investigated using scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The photocatalytic experiment results showed that the optimum Ge catalyst layer thickness significantly improved the rhodamine B (RhB) degradation efficiency of the nanowires. The TiO2 nanowires grown using a 40-nm-thick Ge layer could degrade 74% of RhB after 5 h of ultraviolet irradiation. In addition, the TiO2 nanowires exhibited excellent electron field emission performance as compared to the TiO2 nanocrystals grown without the Ge catalyst layer. The results suggested that TiO2 nanowires grown using a Ge catalyst layer are promising materials for next-generation electronic emitters and photocatalytic systems.