Kreft, S.; Radnik, J.; Rabeah, J.; Agostini, G.; Pohl, M.; Gericke, E.; Hoell, A.; Beller, M.; Junge, H.; Wohlrab, S.: Dye activation of heterogeneous Copper(II)-Species for visible light driven hydrogen generation. International Journal of Hydrogen Energy 44 (2019), p. 28409-28420
10.1016/j.ijhydene.2019.04.006

Abstract:
Heterogeneous Cu catalysts are widely used in photocatalytic hydrogen generation. The typical working mode includes the transfer of photo-induced charges from a semiconductor to CuO which itself is reduced to Cu2O to initiate the catalytic cycle. In this contribution a photosensitizer (dye), excited by visible light absorption, was used to transfer an electron to the CuO which after reduction catalyzes the water reduction to hydrogen. Several copper(II)-catalysts on high surface silica were prepared by impregnation or precipitation and applied in photocatalytic water reduction. The best catalyst CuO(Cl0.1)/SiO2, synthesized via incipient wetness impregnation of CuCl2 in MCM-41 and a following precipitation with NaOH, achieved a 6 times higher activity (1702 mmol h1 g1) compared to a previously investigated copper system (280 mmol h1 g1 for CuI) under the same reaction conditions. All materials were fully characterized by XRD, TEM and N2 sorption and further by magnetic resonance and X-ray methods EPR, ASAXS and XAS. In situ measurements evidenced a reduction of the initial Cu(II)-species, which confirms the (proposed) photocatalytic mechanism.