Fuyu Wen

Enhancement of photocatalytic H2 evolution on CdS by loading MoS2 as Cocatalyst under visible light irradiation.

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.

Hybrid Artificial Photosynthetic Systems Comprising Semiconductors as Light Harvesters and Biomimetic Complexes as Molecular Cocatalysts

Solar fuel production through artificial photosynthesis may be a key to generating abundant and clean energy, thus addressing the high energy needs of the worlds 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 H2/O2 evolution and CO2 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.

Visible light driven hydrogen production from a photo-active cathode based on a molecular catalyst and organic dye-sensitized p-type nanostructured NiO

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.

Visible light driven H2 production in molecular systems employing colloidal MoS2 nanoparticles as catalyst

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.

A Hybrid Photocatalytic System Comprising ZnS as Light Harvester and an [Fe2S2] Hydrogenase Mimic as Hydrogen Evolution Catalyst

Photo opportunity: A highly efficient and stable hybrid artificial photosynthetic H(2) evolution system is assembled by using a semiconductor (ZnS) as light-harvester and an [Fe(2)S(2)] hydrogenase mimic ([(μ-SPh-4-NH(2) )(2) Fe(2) (CO)(6)]) as catalyst for H(2) evolution. Photocatalytic H(2) production is achieved with more than 2607 turnovers (based on [Fe(2)S(2)]) and an initial turnover frequency of 100 h(-1) through the efficient transfer of photogenerated electrons from ZnS to the [Fe(2)S(2)] complex.

Roles of cocatalysts in semiconductor-based photocatalytic hydrogen production

A photocatalyst is defined as a functional composite material with three components: photo-harvester (e.g. semiconductor), reduction cocatalyst (e.g. for hydrogen evolution) and oxidation cocatalyst (e.g. for oxidation evolution from water). Loading cocatalysts on semiconductors is proved to be an effective approach to promote the charge separation and transfer, suppress the charge recombination and enhance the photocatalytic activity. Furthermore, the photocatalytic performance can be significantly improved by loading dual cocatalysts for reduction and oxidation, which could lower the activation energy barriers, respectively, for the two half reactions. A quantum efficiency (QE) as high as 93 per cent at 420 nm for H2 production has been achieved for Pt–PdS/CdS, where Pt and PdS, respectively, act as reduction and oxidation cocatalysts and CdS as a photo-harvester. The dual cocatalysts work synergistically and enhance the photocatalytic reaction rate, which is determined by the slower one (either reduction or oxidation). This work demonstrates that the cocatalysts, especially the dual cocatalysts for reduction and oxidation, are crucial and even absolutely necessary for achieving high QEs in photocatalytic hydrogen production, as well as in photocatalytic water splitting.

Photocatalytic Splitting of H2S to Produce Hydrogen by Gas-Solid Phase Reaction

Hydrogen production by gas-solid phase photocatalytic splitting of H2S was investigated on five semiconductor photocatalysts including TiO2, CdS, ZnS, ZnO, and ZnIn2S4. ZnS shows the highest rate of hydrogen production under the identical conditions. Loading Ir on ZnS can effectively promote the hydrogen production. The addition of Cu2+ during the ZnS preparation significantly enhances the photocatalytic activity of the catalyst for hydrogen production.