Abstract : Hydrogen is considered as an energy carrier of high potentiality to face problems related to the climate change and the depletion of fossil resources. Among the necessary improvements, its production through clean processes is still a big challenge. The water photolysis process under sun irradiation is one of the most relevant ones (usage of renewable energy, abundant and cheap catalyst, room temperature...). The energetic efficiency is however still too low. The objective of this thesis is to study the impact of the morphology and the nanostructure of the reference semiconductor - titanium dioxide (TiO2) - on its performa nce for water splitting. To this end, three types of radically different anatase nanostructures have been prepared and finely characterized: i) nanoparticles (precipitation followed by hydrothermal crystallisation), ii) elongated nanowire-like structures ("Kasuga" process) and iii) aerogels and xerogels like nanostructured materials. The most original ones have been doped following literature processes in order to get vanadium doped nanowires and nitrogen doped aerogels and xerogels. Slurries of the most promising materials have then been evaluated for hydrogen evolution, with or without platinum co-catalyst. It came out from this study that the nanowires and the aerogels were relevant for the foreseen application. Under the chosen experimental conditions, aerogels showed a conversion activity clearly higher than that of the reference photocatalyst (a mixture of anatase and rutile).