Photobiological hydrogen production has recently attracted interest in terms of being a potential source for an alternative energy carrier. Especially the natural light driven hydrogen metabolism of unicellular green algae appears as an attractive blueprint for a clean and potentially unlimited dihydrogen source. However, the efficiency of in vivo systems is limited by physiological and evolutionary constraints and scientists only begin to understand the regulatory networks influencing cellular hydrogen production. A growing number of projects aim at circumventing these limitations by focusing on semi-artificial systems. They reconstitute parts of the native electron transfer chains in vitro, combining photosystem I as a photoactive element with a proton reducing catalytic element such as hydrogenase enzymes or noble metal nanoparticles. This review summarizes various approaches and discusses limitations that have to be overcome in order to establish economically applicable systems. (C) 2011 Elsevier Ltd. All rights reserved.