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Yu W.,King Abdullah University of Science and Technology | Yu W.,Changchun University of Science and Technology | Isimjan T.,Solar and Photovoltaics Engineering Research Center | Lin B.,King Abdullah University of Science and Technology | Takanabe K.,King Abdullah University of Science and Technology
IOP Conference Series: Materials Science and Engineering | Year: 2014

Noble metals as cocatalysts for hydrogen evolution are widely investigated for semiconductor photocatalytic water splitting. In this paper, we present a novel way to attach not only noble metals, but also transitional metals onto CdS nanocrystals as cocatalysts for hydrogen evolution. The hydrogen evolution performances for each metal were compared and result shows that Pd attached CdS gives the highest hydrogen evolution rate of 250 μmol/h. The amounts of metal ions attached on the surface were measured by inductively coupled plasma optical emission spectrometry (ICP-OES). This work confirms that surface modification is a promising way of attaching cocatalysts onto semiconductor photocatalysts. Source


Yu W.,Changchun University of Science and Technology | Isimjan T.,Solar and Photovoltaics Engineering Research Center | Gobbo S.D.,Solar and Photovoltaics Engineering Research Center | Anjum D.H.,Imaging and Characterization core Laboratory KAUST | And 6 more authors.
ChemSusChem | Year: 2014

A simple and versatile method for the preparation of photocatalyst particulates modified with effective cocatalysts is presented; the method involves the sequential soaking of photocatalyst particulates in solutions containing bifunctional organic linkers and metal ions. The modification of the particulate surfaces is a universal and reproducible method because the molecular linkers utilize strong covalent bonds, which in turn result in modified monolayer with a small but controlled quantity of metals. The photocatalysis results indicated that the CdS with likely photochemically reduced Pd and Ni, which were initially immobilized via ethanedithiol (EDT) as a linker, were highly efficient for photocatalytic hydrogen evolution from Na2S-Na2SO3-containing aqueous solutions. The method developed in this study opens a new synthesis route for the preparation of effective photocatalysts with various combinations of bifunctional linkers, metals, and photocatalyst particulate materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Sun J.,Solar and Photovoltaics Engineering Research Center | Yang Y.,King Abdullah University of Science and Technology | Khan J.I.,Solar and Photovoltaics Engineering Research Center | Alarousu E.,Solar and Photovoltaics Engineering Research Center | And 4 more authors.
ACS Applied Materials and Interfaces | Year: 2014

We explored for the first time the ultrafast carrier trapping of a metal-doped titanium dioxide (TiO2) semiconductor using broad-band transient absorption (TA) spectroscopy with 120 fs temporal resolution. Titanium dioxide was successfully doped layer-by-layer with two metal ions, namely tungsten and cobalt. The time-resolved data demonstrate clearly that the carrier trapping time decreases progressively as the doping concentration increases. A global-fitting procedure for the carrier trapping suggests the appearance of two time components: a fast one that is directly associated with carrier trapping to the defect state in the vicinity of the conduction band and a slow one that is attributed to carrier trapping to the deep-level state from the conduction band. With a relatively long doping deposition time on the order of 30 s, a carrier lifetime of about 1 ps is obtained. To confirm that the measured ultrafast carrier dynamics are associated with electron trapping by metal doping, we explored the carrier dynamics of undoped TiO2. The findings reported here may be useful for the implementation of high-speed optoelectronic applications and fast switching devices. © 2014 American Chemical Society. Source

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