This communication presents our recent results that the activity of photocatalytic H2 production can be significantly enhanced when a small amount of MoS2 is loaded on CdS as cocatalyst. The MoS2/CdS catalysts show high rate of H2 evolution from photocatalytic re-forming of lactic acid under visible light irradiation. The rate of H2 evolution on CdS is increased by up to 36 times when loaded with only 0.2 wt % of MoS2, and the activity of MoS2/CdS is even higher than those of the CdS photocatalysts loaded with different noble metals, such as Pt, Ru, Rh, Pd, and Au. The junction formed between MoS2 and CdS and the excellent H2 activation property of MoS2 are supposed to be responsible for the enhanced photocatalytic activity of MoS2/CdS.

Photocatalytic H 2 production on MoS 2 /CdS photocatalysts in the presence of different sacrificial reagents under visible light (λ > 420 nm) has been investigated. The transformation process of the Mo species loaded on CdS, together with the junctions formed between MoS 2 and CdS, was clearly demonstrated with X-ray photoelectron spectroscopy and transmission electron microscopy. Photocatalytic H 2 evolution was optimized for MoS 2 /CdS catalysts. The 0.2 wt % MoS 2 /CdS catalyst calcined at 573 K achieves the highest overall activity for H 2 evolution, and the 0.2 wt % MoS 2 /CdS catalyst demonstrates even higher activity than the 0.2 wt % Pt/CdS, irrespective of different sacrificial reagents used. The junctions formed between MoS 2 and CdS play an important role in enhancing the photocatalytic activity of MoS 2 /CdS catalysts. Electrochemical measurements indicate that MoS 2 is an excellent H 2 evolution catalyst, which is another very important factor responsible for the enhancement of the photocatalytic activity of MoS 2 /CdS catalysts.

A molecular device with a photocathode for hydrogen generation has been successfully demonstrated, based on an earth abundant and inexpensive p-type semiconductor NiO, an organic dye P1 and a cobalt catalyst Co1.

S olar fuel production through artificial photosynthesis may be a key to generating abundant and clean energy, thus addressing the high energy needs of the world's expanding population. As the crucial components of photosynthesis, the artificial photosynthetic system should be composed of a light harvester (e.g., semiconductor or molecular dye), a reduction cocatalyst (e.g., hydrogenase mimic, noble metal), and an oxidation cocatalyst (e.g., photosystem II mimic for oxygen evolution from water oxidation). Solar fuel production catalyzed by an artificial photosynthetic system starts from the absorption of sunlight by the light harvester, where charge separation takes place, followed by a charge transfer to the reduction and oxidation cocatalysts, where redox reaction processes occur. One of the most challenging problems is to develop an artificial photosynthetic solar fuel production system that is both highly efficient and stable. The assembly of cocatalysts on the semiconductor (light harvester) not only can facilitate the charge separation, but also can lower the activation energy or overpotential for the reactions. An efficient light harvester loaded with suitable reduction and oxidation cocatalysts is the key for high efficiency of artificial photosynthetic systems.In this Account, we describe our strategy of hybrid photocatalysts using semiconductors as light harvesters with biomimetic complexes as molecular cocatalysts to construct efficient and stable artificial photosynthetic systems. We chose semiconductor nanoparticles as light harvesters because of their broad spectral absorption and relatively robust properties compared with a natural photosynthesis system. Using biomimetic complexes as cocatalysts can significantly facilitate charge separation via fast charge transfer from the semiconductor to the molecular cocatalysts and also catalyze the chemical reactions of solar fuel production. The hybrid photocatalysts supply us with a platform to study the photocatalytic mechanisms of H 2 /O 2 evolution and CO 2 reduction at the molecular level and to bridge natural and artificial photosynthesis. We demonstrate the feasibility of the hybrid photocatalyst, biomimetic molecular cocatalysts, and semiconductor light harvester for artificial photosynthesis and therefore provide a promising approach for rational design and construction of highly efficient and stable artificial photosynthetic systems.

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Colloidal MoS(2) nanoparticles with diameters of less than 10 nm were prepared with a simple solvothermal method and demonstrated high efficiency in catalyzing H(2) evolution in Ru(bpy)(3)(2+)-based molecular systems under visible light.

Zinc orthogermanate was prepared via a hydrothermal method and a remarkable synergistic effect on the photocatalytic activity for overall water splitting was found for Zn 2 GeO 4 co-loaded with noble metals (Pt, Rh, Pd, Au) and metal oxides (RuO 2 , IrO 2 ). The photocatalytic activity of Pt-RuO 2 /Zn 2 GeO 4 for overall water splitting is 2.2 times of Pt/Zn 2 GeO 4 and 3.3 times of RuO 2 /Zn 2 GeO 4 . Photocatalytic half reactions evaluation of water splitting for H 2 and O 2 productions shows that Pt plays the major roles in H 2 production and RuO 2 promotes the O 2 production. The roles and valence states of co-catalysts and the mechanism of photocatalytic reaction are discussed.