Pd/ZnO catalysts with different origins for high chemoselectivity in acetylene semi-hydrogenation

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The heterogeneity of active sites is the main obstacle for selectivity control in heterogeneous catalysis. Single atom catalysts (SACs) with homogeneous isolated active sites are highly desired in chemoselective transformations. In this work, a Pd 1 /ZnO catalyst with single-atom dispersion of Pd active sites was achieved by decreasing the Pd loading and reducing the sample at a relatively low temperature. The Pd 1 /ZnO SAC exhibited excellent catalytic performance in the chemoselective hydrogenation of acetylene with comparable chemoselectivity to that of PdZn intermetallic catalysts and a greatly enhanced utilization of Pd metal. Such unusual behaviors of the Pd 1 /ZnO SAC in acetylene semi-hydrogenation were ascribed to the high-valent single Pd active sites, which could promote electrostatic interactions with acetylene but restrain undesired ethylene hydrogenation via the spatial restrictions of σ-chemical bonding toward ethylene. A Pd-based single atom catalyst was achieved on a ZnO support, which exhibits excellent catalytic performances with a comparably high chemoselectivity but a different origin to that of PdZn catalysts in acetylene semi-hydrogenation.