Photocatalytic H-2 production on hybrid catalyst system composed of inorganic semiconductor and cobaloximes catalysts

An artificial photocatalytic system mimicking photosystem I (PSI) has been assembled using semiconductor (CdS) as photosensitizer, cobaloximes (Co-III complexes) as H-2 evolution catalysts, and triethanolamine (TEOA) as sacrificial electron donor. This artificial photocatalytic system shows high hydrogen evolution activity (turnover number up to 171 based on Co-III(dmgH)(2)pyCl 1) under visible light irradiation. The apparent quantum efficiency (QE) for 1/CdS hybrid photocatalytic system in acetonitrile solution at 420 nm is calculated to be 9.1%. The interfacial electron transfer from photoexcited CdS to Co-III complexes is very efficient through the weak adsorption of Co-III complexes on CdS. The adsorption of 1 on CdS in acetonitrile fits Langmuir equation, the maximum monolayer adsorption capacity is 3 x 10(-3) mmol g(-1), which means most of 1 are in the solution. The rate of hydrogen production exhibits a quadratic dependence on the total concentration of I. Therefore, a bimetallic catalysis pathway is proposed. The efficient electron transfer, the broad electronic absorption character of CdS photosensitizer as well as the H-2 evolution ability of Co-III complexes, account for the high photocatalytic activity of this hybrid photocatalytic system. (C) 2011 Elsevier Inc. All rights reserved