Improving gold catalysis of nitroarene reduction with surface Pd

Nitroarene reduction reactions are commercialized catalytic processes that play a key role in the synthesisof many products including medicines, rubbers, dyes, and herbicides. Whereas bimetallic compositionshave been studied, a better understanding of the bimetallic structure effects may lead to improved indus-trial catalysts. In this work, the influence of surface palladium atoms supported on 3-nm Au nanoparticles(Pd-on-Au NPs) on catalytic activity for 4-nitrophenol reduction is explored. Batch reactor studies indi-cate Pd-on-Au NPs exhibit maximum catalytic activity at a Pd surface coverage of 150 sc%, with aninitial turnover frequency of ~3.7 mol-nitrophenol/mol-metalsurface/s, which was ~5.5× and ~13× moreactive than pure Au NPs and Pd NPs, respectively. Pd NPs, Au NPs, and Pd-on-Au NPs below 175 sc%show compensation behavior. Three-dimensional Pd surface ensembles (with ~4–5 atoms) previouslyidentified through X-ray adsorption spectroscopy provide the active sites responsible for the catalyticmaximum. These results demonstrate the ability to adjust systematically a structural feature (i.e., Pdsurface coverage) to yield a more active material.