Heterogeneous copper particles have been widely investigated in photocatalytic reduction processes to produce hydrogen. In this contribution, copper nanoparticles were in situ generated and supported on different C- and SiO2-based additives in the presence of an iridium photosensitizer (PS), which itself was activated by visible light absorption. Thereby, the influence of the supports on the formation of the active species and their performance as water reduction catalysts were studied. The additives ensure heterogeneous nucleation leading to lower sizes of the formed copper particles and prevent their further growth during the reaction which was verified by STEM analysis. Consequently, the hydrogen productivity in the presence of the supports was enhanced and the best carbon material rGO(H-2) revealed a 3 times higher activity compared to the non-supported system after 20 h. Photoluminescence measurements confirmed the proposed reductive quenching mechanism in this system and suggested that rGO(H-2) mediates reoxidation of the PS. However, in the presence of the ligand 2,2'-bipyridine (bpy) the application of the silica MCM-41 showed a fourfold increase of hydrogen evolution compared to the non-supported system, which was still active after 160 h and could be successfully reused in recycling experiments. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.