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  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 h
1 g
1) compared to a previously investigated copper system (280 mmol h
1 g
1 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.