2 research outputs found
Redispersion of Gold Supported on Oxides
Although many gold heterogeneous catalysts have been
shown to exhibit
significant activity and high selectivity for a wide range of reactions
in both the liquid and gas phases, they are prone to irreversible
deactivation. This is often associated with sintering or loss of the
interaction of the gold with the support. Herein, we report on the
use of methyl iodide as a method of dispersing gold nanoparticles
supported on silica, titania, and alumina supports. In the case of
titania- and alumina-based catalysts, the gold was transformed from
nanometer particles into small clusters and some atomically dispersed
gold. In contrast, although there was a drop in the gold particle
size on the silica support following CH<sub>3</sub>I treatment, the
size remained in the submicrometer range. The structural changes were
correlated with changes in the selectivity and activity for ethanol
dehydration and benzyl alcohol oxidation. From these observations,
it is clear that this treatment provides a method by which deactivated
gold catalysts can be reactivated via redispersion of the gold
Designer Titania-Supported Au–Pd Nanoparticles for Efficient Photocatalytic Hydrogen Production
Photocatalytic hydrogen evolution may provide one of the solutions to the shift to a sustainable energy society, but the quantum efficiency of the process still needs to be improved. Precise control of the composition and structure of the metal nanoparticle cocatalysts is essential, and we show that fine-tuning the Au–Pd nanoparticle structure modifies the electronic properties of the cocatalyst significantly. Specifically, Pd<sub>shell</sub>–Au<sub>core</sub> nanoparticles immobilized on TiO<sub>2</sub> exhibit extremely high quantum efficiencies for H<sub>2</sub> production using a wide range of alcohols, implying that chemical byproducts from the biorefinery industry can be used as feedstocks. In addition, the excellent recyclability of our photocatalyst material indicates a high potential in industrial applications. We demonstrate that this particular elemental segregation provides optimal positioning of the unoccupied d-orbital states, which results in an enhanced utilization of the photoexcited electrons in redox reactions. We consider that the enhanced activity observed on TiO<sub>2</sub> is generic in nature and can be transferred to other narrow band gap semiconductor supports for visible light photocatalysis