Hydrogen generated through the photochemical cleavage of water using a source of renewable (e.g. solar) energy is considered to be an environmentally friendly chemical fuel, due to the fact that the combustion of hydrogen generates only water again, which neither results in air pollution nor leads to the emission of greenhouses gases. Photocatalytic materials required for water cleavage should be able to perform at least two fundamental functions: (i) a light harvesting function which is required to provide maximal absorption of the solar energy spectrum and (ii) a catalytic function which is required for water decomposition. Multi-component systems, i.e. combinations of different semiconductors and/or metals, are expected to exhibit improved efficiencies since they allow for a more efficient use of the solar spectrum, for interfacial charge transfer processes and an improvement of photocatalytic reactions. Crucially important for their successful design is the detailed understanding of the underlying processes at the interfaces of these multicomponent systems. Advances in solution-phase colloidal synthesis and self-assembly of nanomaterials introduced entirely new ways of controlling the size, shape, arrangement, and topology of such colloidal heterostructures, enabling complex systems to be created by design with nanometer precision. We review our efforts on the wet-chemical synthesis of hybrid structures comprising semiconductor nanoctystals decorated with metal co-catalysts [1], and demonstrate the ability to improve charge generation and separation at the interfaces for the efficient photocatalytic generation of hydrogen from water [2,3].[1] A. Vaneski, J. Schneider, A. S. Susha, A. L. Rogach. Colloidal Hybrid Nanostructures Based on II-VI Semiconductor Nanocrystals for Photocatalytic Hydrogen Generation. J. Photochem. Photobiol. C. Photochem. Rev., 2014, 19, 52-61[2] J. Schneider, A. Vaneski, G. R. Pesch, A. S. Susha, W. Y. Teoh, A. L. Rogach. Enhanced Hydrogen Evolution Rates at High pH with a Colloidal Cadmium Sulphide – Platinum Hybrid System. APL Mater. 2014, 2, 126102[3] T. Simon, N. Bouchonville, M. J. Berr, A. Vaneski, A. Adrovic, D. Volbers, R. Wyrwich, M. Döblinger, A. S. Susha, A. L. Rogach, F. Jäckel, J. K. Stolarczyk, J. Feldmann. Redox Shuttle Mechanism Enhances Photocatalytic H2 Generation on Ni-Decorated CdS Nanorods. Nature Mat. 2014, 13, 1013-1018