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

Two new hybrid molybdenum(IV) Mo3S7 cluster complexes derivatized with diimino ligands have been prepared by replacement of the two bromine atoms of [Mo3S7Br6]2− by a substituted bipyridine ligand to afford heteroleptic molybdenum(IV) Mo3S7Br4(diimino) complexes. Adsorption of the Mo3S7 cores from sample solutions on TiO2 was only achieved from the diimino functionalized clusters. The adsorbed Mo3S7 units were reduced on the TiO2 surface to generate an electrocatalyst that reduces the overpotential for the H2 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 TiO2 nanoparticles show a high photocatalytic activity for H2 production in the presence of Na2S/Na2SO3 as a sacrificial electron donor system.

The financial support of the Spanish Ministerio de Economia y Competitividad (MINECO) (Grant CTQ2011-23157), Fundació Bancaixa-UJI (research project P1.1B2013-19), and Generalitat Valenciana (Prometeo/2014/022 and ACOMP/2014/274) is gratefully acknowledged. R.G. and T. L.-V. also acknowledge the MINECO for financial support through projects MAT2012-37676 (Fondos FEDER) and PRI-PIBIN-2011-0816. The authors also thank the Servei Central d’Instrumentació Cientifica (SCIC) of the Universitat Jaume I for providing us with NMR spectroscopy and mass spectrometry facilities and the SSTTI of the Universitat d’Alacant for the XPS measurements (UAUSTI13-05). D.R. thanks the Spanish Ministerio de Economía y Competetividad for a predoctoral fellowship. A.G. thanks the Spanish Ministerio de Ciencia e Innovación (MICINN) for a postdoctoral fellowship and the Russian Foundation for Basic Research (projects N8 12-03-00305, 12-03-33028). E.K. acknowledges support of SB RAS (project #35), the Ministry of Education and Science of the Russian Federation (SP 85.2012.1 and NSh-1183.2014.3), and the Skolkovo Foundation (Grant Agreement for Russian educational organization No.1 on 28.11.2013).