High Catalytic Activity and Chemoselectivity of Sub-nanometric Pd Clusters on Porous Nanorods of CeO₂ for Hydrogenation of Nitroarenes

Abstract

Sub-nanometric Pd clusters on porous nanorods of CeO2 (PN-CeO2) with a high Pd dispersion of 73.6% exhibit the highest catalytic activity and best chemoselectivity for hydrogenation of nitroarenes to date. For hydrogenation of 4-nitrophenol, the catalysts yield a TOF of ∼44059 h(-1) and a chemoselectivity to 4-aminophenol of >99.9%. The superior catalytic performance can be attributed to a cooperative effect between the highly dispersed sub-nanometric Pd clusters for hydrogen activation and unique surface sites of PN-CeO2 with a high concentration of oxygen vacancy for an energetically and geometrically preferential adsorption of nitroarenes via nitro group. The high concentration of surface defects of PN-CeO2 and large Pd dispersion contribute to the enhanced catalytic activity for the hydrogenation reactions. The high chemoselectivity is mainly governed by the high Pd dispersion on the support. The catalysts also deliver high catalytic activity and selectivity for nitroaromatics with various reducible substituents into the corresponding aminoarenes.

Band gap energies for white nanosheets/yellow nanoislands/purple nanorods of CeO2

“…3(b) and (c) demonstrated indirect and direct photon band gap energies of 1.8 and 2.1 eV for the purple CeO 2 nanorods, respectively. [32][33][34] In order to further investigate the reason for the differences in the photon band energies among the samples, the XPS analysis technique was conducted to understand the electron states on the surfaces of the fabricated samples. 3(d) highlights the UV absorption spectrum for the yellow CeO 2 nanoislands.…”

Synthesis and catalytic property of urania-palladium-graphene nanohybrids

“…The shift of edge energy is tiny, so it might not be easily observed in the XPS profiles. Previous studies have shown that nitro groups can be easily adsorbed on the basic or reducible supports [43][44][45]. Hence, UO2 tends to adsorb 4-nitrophenol, which then can be further reduced by the injected electrons on UO2.…”

Regenerable Subnanometer Pd Clusters on Zirconia for Highly Selective Hydrogenation of Biomass-Derived Succinic Acid in Water

“…The smaller clusters may create more active sites around the metal-support interface. Conversely, the growth of particles likely loses the metal-support interface that gradually inhibits the ability of the adsorbed species to turn over at the metal-support boundary [47]. Furthermore, very small metal clusters with electronic quantum size effects, in other words the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap, lead to lower activation barriers of the reaction, which have a decisive role in the increase of reactivity [48].…”