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Intermetallic structures with atomic precision for selective hydrogenation of nitroarenes

Pei, Yuchen, Qi, Zhiyuan, Goh, Tian Wei, Wang, Lin-Lin, Maligal-Ganesh, Raghu V., MacMurdo, Heather L., Zhang, Shiran, Xiao, Chaoxian, Li, Xinle, (Feng) Tao, Franklin, Johnson, Duane D., Huang, Wenyu
Journal of catalysis 2017 v.356 pp. 307-314
adsorption, alloys, catalysts, density functional theory, dissociation, geometry, hydrogen, hydrogenation, nanoparticles, porous media, silica
Bridging the structure-properties relationship of bimetallic catalysts is essential for the rational design of heterogeneous catalysts. Different from random alloys, intermetallic compounds (IMCs) present atomically-ordered structures, which is advantageous for catalytic mechanism studies. We used Pt-based intermetallic nanoparticles (iNPs), individually encapsulated in mesoporous silica shells, as catalysts for the hydrogenation of nitroarenes to functionalized anilines. With the capping-free nature and ordered atomic structure, PtSn iNPs show >99% selectivity to hydrogenate the nitro group of 3-nitrostyrene albeit with a lower activity, in contrast to Pt3Sn iNPs and Pt NPs. The geometric structure of PtSn iNPs in eliminating Pt threefold sites hampers the adsorption/dissociation of molecular H2 and leads to a non-Horiuti-Polanyi hydrogenation pathway, while Pt3Sn and Pt surfaces are saturated by atomic H. Calculations using density functional theory (DFT) suggest a preferential adsorption of the nitro group on the intermetallic PtSn surface contributing to its high selectivity.