TiO2 nanostructures are well known as important functional materials because of their applications in high-efficiency photovoltaics, photocatalysis, chemical sensors, nonlinear optics, self-cleaning surfaces, water recycling and other fields [1]. Therefore, techniques for the fabrication of defined TiO2 nanostructures on large surface areas and appropriate methods for their characterization and modification are of growing interest. Layers of TiO2 of different surface roughness can be fabricated chemical and physical methods like sputtering [2], chemical vapor deposition [3], or sol-gel [4]. A particular, convenient method for the formation of nanotubes is the nano-anodization of Ti [5,6]. The use of TiO2 nanotubes generated by this approach for photocatalysis applications was demonstrated by several authors [7,8]. Here we report on recent studies of the photocatalytic activity (PCA) of TiO2 nanotubes grown on Ti bulk material at different electrolytes and compare the data with respect to the standard reference material Pilkington Activ™ [9]. It will be shown that the best materials show a significant enhancement of the PCA (up to a factor of 2 compared to the reference). Possible reasons for the enhancement are discussed. Beside linear absorption measurements, spectroscopic studies of femtosecond-laser induced photoluminescence and nonlinear absorption of the materials were performed to gain further insight in the relevant energy transfer mechanisms.