Particle-Size-Dependent Electronic Metal–Support Interaction in Pd/TiO2 Catalysts for Selective Hydrogenation of 3-Nitrostyrene

The Pd/TiO2 catalysts with varying Pd nanoparticle sizes are used to study the control of selectivity toward the hydrogenation of 3-nitrostyrene (3-NS). Our results show the selectivities of 3-vinylanilline (3-VA) rise by decreasing the particle size, while the selectivity of 3-ethylnitrobenzene (3-EN) is the opposite. However, over the Pd/SiO2 catalysts, 3-EN moieties are the dominant product regardless of their differences in particle size. We find that the electronic interactions between Pd NPs and the TiO2 support rise by decreasing particle size, as a result, creating more admetals on the Pd NPs in contact with TiO2, which favorably adsorb the nitro group of 3-NS, thus resulting in enhanced selectivity of 3-VA. However, the classical strong metal–support interactions (SMSI) induced by reduction at elevated temperatures play no significant role in the controlling of selectivities of 3-VA and 3-EN. The SiO2-supported Pd NPs without electronic metal–support interactions (EMSIs) prefer the reduction of the vinyl group of 3-NS. This work underlines the importance of EMSI governing the selectivity for hydrogenation of unsaturated nitroarene reactions.