Mechanism of Selective Hydrogenation of 4-Nitrophenylacetylene Using Pt–Zn Intermetallic Nanoparticles: The Role of Hydrogen Coverage

Abstract

Selective hydrogenation of the nitroaromatics containing other reducible functional groups is very important, but the mechanism still remains controversial. Inspired by recent work on the excellent transformation of 4nitrophenylacetylene into 4-aminophenylacetylene using the Pt−Zn intermetallic nanoparticles as catalysts (Nat. Commun. 2019, 10, 3787), theoretical investigations have been performed to unravel the mechanism. Both the positive Zn species and the moderate hydrogen coverage were found to profoundly affect the adsorption structures and the bonding strength of the functional groups, thus dramatically affecting the adsorption selectivity. In contrast to the bare surface that the hydrogenation of the −CC group competes with the −NO 2 group, the overall barrier for the hydrogenation of the −NO 2 group on the 12H−PtZn (022̅ ) model is 0.90 eV, much lower than those of the −CC group for various intermediates by at least 0.28 eV, well explaining the experimental observation of the very high selectivity and conversion. The computational results strongly support that the pre-adsorbed hydrogen greatly changes the adsorption modes of the reactants and alters the reaction mechanism and, therefore, should be carefully evaluated for the hydrogenation of nitroaromatics on metal surfaces.

High Metal Loading, Two Nanometer-Sized Platinum Zinc Intermetallic Nanoparticles from Atomically Dispersed Precursors for Hydrogenation Reaction

“…Structurally ordered intermetallic nanoparticles (NPs) have attracted much interest as a new generation of catalysts with promising activity and durability, especially in several fast-growing fields, such as electrocatalysis − and selective hydrogenation. , Incorporation of non-precious metals (M) into precious metals such as platinum (Pt) is desirable because of the considerations of not only sustainability and elemental abundance but also improved activity and stability . It is common that Pt intermetallic NPs could achieve higher catalytic activity than pure Pt after the optimization of compositions and structures .…”