This photocatalytic H 2 -production activity was clearly higher in the carbon dot-modified TiO 2 nanostructures than in the unmodified form, especially when irradiated to a 300W Xe lamp, the optimum carbon dot-modified TiO2 nanoparticles and nanotubes exhibited H2-production rates of 75.5 and 246.1 µmol h -1 g -1 , respectively, which are 21.6 and 3.3 times more than those of pure TiO2 nanoparticles and nanotubes (Fig. ). The key factor for the performance increase of carbon dot-modified TiO2 nanostructures was the exceptional electron transport capability of carbon dots.