Effective Ensemble of Pt Single Atoms and Clusters over the (Ni,Co)(OH)2 Substrate Catalyzes Highly Selective, Efficient, and Stable Hydrogenation Reactions

A Pt-Ni-Co catalyst was synthesized with Pt single atoms and atomic clusters (SAACs) dispersed over (Ni,Co)(OH)(2) nanoparticles on a carbon matrix, which leads to high catalytic activity, up to 100% conversion, and selectivity in the hydrogenation of nitroaromatics under moderate conditions (H-2 similar to 1.0 MPa and <= 40 degrees C). A synergistically coordinated ensemble effect of the Pt SAACs is identified with the strongly polarized Pt single atoms preferentially adsorbing the -NO2 and the Pt clusters adsorbing and homolytically dissociating H-2 molecules, and the H species then readily move to the adsorbed -NO2 group, overcoming a much reduced energy barrier on the (Ni,Co)(OH)(2), enhancing the reaction rate by ca. 50 times. The approach not only reveals the coordinated ensemble catalysis mechanism of SAACs but also provides a strategy of developing highly efficient and selective catalysts by fine tuning of the electronic microenvironment from single atoms to atomic clusters co-located over a multimetallic substrate. The demonstrated case for nitroarenes can be readily applied for other species containing -NO2 or other easily hydrogenated groups (such as C=C, C Z, and C=O).