Photogeneration of Hydrogen from Water by Hybrid Molybdenum Sulfide Clusters Immobilized on Titania

Two new hybrid molybdenum(IV) Mo 3 S 7 cluster complexes derivatized with diimino ligands have been prepared by replacement of the two bromine atoms of [Mo 3 S 7 Br 6 ] 2− by a substituted bipyridine ligand to afford heteroleptic molybdenum(IV) Mo 3 S 7 Br 4 (diimino) complexes. Adsorption of the Mo 3 S 7 cores from sample solutions on TiO 2 was only achieved from the diimino functionalized clusters. The adsorbed Mo 3 S 7 units were reduced on the TiO 2 surface to generate an electrocatalyst that reduces the overpotential for the H 2 evolution reaction by approximately 0.3 V (for 1 mA cm −2 ) with a turnover frequency as high as 1.4 s −1 . The nature of the actual active molybdenum sulfide species has been investigated by X‐ray photoelectron spectroscopy. In agreement with the electrochemical results, the modified TiO 2 nanoparticles show a high photocatalytic activity for H 2 production in the presence of Na 2 S/Na 2 SO 3 as a sacrificial electron donor system.