Abstract : Polyoxometalates (POMs) constitute a unique class of inorganic metal-oxygen clusters with a wide variety of properties. They have for example good advantages for applications in photocatalysis, particularly for the reduction of metallic cations. However, these compounds absorb principally in the UV spectral domain, requiring consequently a light activation in this spectral domain. The aim of this work has been to show the ability to use the catalytic properties of POMs in using the visible light, in combining POM with visible photosensitizers like porphyrins. Several hybrid porphyrin(s)-POM systems have been successively studied. First, we have investigated the photocatalytic properties of such systems in homogeneous media. For that, three kinds of assemblies based on different interactions, have been studied: electrostatic interactions, coordination interactions, and covalent bonds. Afterwards, the study has been extended to supported systems, in order to carry out heterogeneous catalysis. Two different approaches have been considered: multilayers systems and copolymers porphyrin-POM obtained by electropolymerization. All these systems have been the object of a thorough physical chemistry study, particularly by electrochemistry, photochemistry (systems in solution), atomic force microscopy (supported systems)... Photocatalytic tests have also been performed. As a first step, Ag(I) ions have been chosen as a model system for photoreduction. Silver nanoparticles with various sizes and shapes have been formed.