Enriching Pt3 ensemble with isolated 3-fold hollow site by crystal-phase engineering of Pt3Fe single-nanoparticle for acetylene hydrogenation

Tuning the crystal-phase of bimetallic particles enables a precise control of catalytically active sites but is experimentally challenged by the averaging ensemble effects that are caused by the particle communications occurred during the crystal-phase transformation. Here, H2-treatment at 773–973 K of Pt3Fe single-nanoparticle, confined by a permeable silica shell, achieved crystal-phase transformation from the disordered A1 phase to the chemically ordered L12 phase. Detailed microscopic and spectroscopic characterizations have identified that the disordered A1 particle possessed contiguously connected large Pt domains while the ordered L12 particle afforded regularly populated Pt3 ensembles surrounded by Fe single-atoms. The isolated 3-fold hollow Pt site in the three-atom ensemble efficiently boosted the adsorption of acetylene, yielding a much higher hydrogenation activity. The reaction rate of the L12 particle was twice of that for the A1 particle. Moreover, the charge transfer from the neighboring Fe single-atoms to the Pt atoms on the L12 particle expedited the desorption of ethylene, promoting the selectivity as well. Overall, both geometric and electronic interactions in the ordered crystal-phase synergistically facilitated the selective hydrogenation of acetylene to ethylene.