For an effective photocatalysis using particular systems a number of elementary processes as well as their coupling to each other must be optimized without severe losses in the number and the chemical potential of the originally generated electron-hole pairs. Light absorption coupled to efficient charge carrier generation and separation may be realized by Janus type photocatalysts which favour vectorial electron-hole pair transport into opposite directions. In addition, recombination reactions of electron hole pairs must be minimized, which will be achieved when the above given separation of electron-hole pairs is favoured by gradients of the electrochemical potentials provided in our case by nanoscopic heterojunctions. Subsequently, electrocatalytic redox reactions reactions must be possible by electron and hole transfer reactions with minimized loss of chemical potential. This will only be possible if the involved charge transfer steps are coupled to selective multi-electron transfer catalysts allowing electron transfer reactions with isoenergetic coupling of their electronic states We have prepared nano-sized semiconductor heterostructures combining oxides with different electron electrochemical potentials (Fermi levels) as e. g. ZnO/SnO2, TiO2/RuO2 or ZnO/RuO2 combinations using a wet sol-gel chemistry approach. The nano catalysts are formed after subsequent annealing steps. The particulates are characterized by TEM, XRD, BET, optical and Raman spectroscopy. In addition, the device structure is analyzed by applying photoelectron spectroscopy to the particles as well as to UHV prepared model interfaces. In all cases the formation of heterostructures with the formation of space charge layers could be proven, which is made responsible for improved charge carrier separation. In all cases we have found a clear correlation of increased photocatalytic activity also with respect to H2 evolution with the particulate heterostructures clearly exceeding the values of Degussa TiO2 25 as well as to the isolated parent photocatalysts. Evidently, electron-hole separation is strongly increased due to the built-in electronic asymmetry of the heterojunction particles. Thus we conclude that the design of advanced photocatalyic nanoparticles needs engineering principles following the same specific design rules controlling charge carrier dynamics as also valid for macroscopic semiconductor heterostructures.