A new application of photocatalysts: synthesis of nano-sized metal and alloy catalysts by a photo-assisted deposition method

Supported Pd catalysts were synthesized using various semiconductor materials by a photo-assisted deposition method under UV-light irradiation. The Pd precursor was deposited and partially reduced by the direct interaction with the photo-excited state of the semiconductor materials, and subsequently transformed into metal particles by H-2 reduction. CO adsorption and Pd K-edge XAFS measurements demonstrated that the mean diameter of the deposited Pd particles can be controlled by the type of employed semiconductor materials. The catalytic activities in the direct synthesis of hydrogen peroxide (H2O2) using H-2 and O-2 gases under atmospheric pressure were strongly dependent on the type of supports. Here, the use of TiO2 comprising a mixed phase of anatase and rutile was the most efficient based on the amount of Pd. The photo-assisted deposition also provides a simple and straightforward method to synthesize PdAu alloy nanoparticles. For the structural model of PdAu nanoparticles, we suggest that most of the Au atoms are preferentially located in the core region, whereas the Pd atoms are preferentially located in the shell region. The PdAu/TiO2 catalysts prepared by the photo-assisted deposition method were shown to perform significantly better than the pure Pd/TiO2 catalysts.