Molecule Saturation Boosts Acetylene Semihydrogenation Activity and Selectivity on a Core‐Shell Ruthenium@Palladium Catalyst

Abstract

Increasing selectivity without the expense of activity is desired but challenging in heterogeneous catalysis. By revealing the molecule saturation and adsorption sensitivity on overlayer thickness, strain, and coordination of Pd-based catalysts from first-principles calculations, we designed a stable Pd monolayer (ML) catalyst on a Ru terrace to boost both activity and selectivity of acetylene semihydrogenation. The least saturated molecule is most sensitive to the change in catalyst electronic and geometric properties. By simultaneously compressing the Pd ML and exposing the high coordination sites, the adsorption of more saturated ethylene is considerably weakened to facilitate the desorption for high selectivity. The even stronger weakening to the least saturated acetylene drives its hydrogenation such that it is more exothermic, thereby boosting the activity. Tailoring the molecule saturation and its sensitivity to structure and composition provides a tool for rational design of efficient catalysts.

Ionic Liquid-Guided One-Step Green Synthesis of Au–Pd Superbranched Trigonal Nanoframes and Their Highly Selective Hydrogenation of 4-Nitrostyrene

“…Bimetallic nanomaterials are frequently used as catalysts in various reactions, such as CO 2 and NO x reduction, oxidation, hydrogenation, dehydrogenation, electrocatalysis, and photocatalysis because of their unique morphology, tunable electronic structures and superior performance, − among which hydrogenation is an important reaction in the chemical industry, biology, medicine, food, and others. ,,, However, for the substances with two or more reducible functional groups, i.e., alkenyl, alkynyl, nitro, carbonyl, and cyano, to purposefully realize the hydrogenation to one targeted group remains a huge challenge, since they all can be hydrogenated. Thus, artistically designing the synthetic strategies to successfully prepare task-specific catalysts for selective hydrogenation is very crucial. ,,− As a concept verification application, 4-nitrostyrene hydrogenation was used as a model reaction to evaluate the catalytic performance of Au–Pd STNFs. Figure a shows two possible hydrogenation pathways of 4-nitrostyrene.…”

“…At the same time, the content of the Pd element is relatively low (11%) in Au–Pd STNFs-1, causing the weaker Pd–Pd metallic bonds. These decrease the surface energy of Pd 0 and give rise to the preferential adsorption of the groups with lower polarity (alkenyl) onto the surface of the catalyst and hydrogenation and the prohibited hydrogenation to the ones with higher polarity (nitro). , In addition, the proportion of metallic elements in catalysts also has obvious effects on the hydrogenation selectivity. , Moreover, the large specific surface area provides adequate active sites, and 2D open frameworks not only make reactive ions/molecules thoroughly accessible to them but also promote the transport and diffusion of ions/molecules in and out of them . Yet, the self-supported structures and large sizes improve their stability and facilitate recycling.…”

“…48,52 In addition, the proportion of metallic elements in catalysts also has obvious effects on the hydrogenation selectivity. 50,53 Moreover, the large specific surface area provides adequate active sites, and 2D open frameworks not only make reactive ions/molecules thoroughly accessible to them but also promote the transport and diffusion of ions/molecules in and out of them. 65 Yet, the self-supported structures and large sizes improve their stability and facilitate recycling.…”

“…Pd NPs are widely used as catalysts in heterogeneous hydrogenation owing to their superior H 2 activation ability and high activity but low selectivity. ,, As an example in Figure e, commercial Pd/C had no selectivity in 4-nitrostyrene hydrogenation, and two reducible groups of double bond and nitro were hydrogenated disorderly. Alternatively, by bringing a second metal to form alloys, ,,, intermetallic compounds, or core–shell structures, ,, the electronic structures and geometric properties of Pd-based catalysts are regulated, whereby the hydrogenation selectivity can be improved. In the present work, the XPS result confirms that there exists obvious electron transfer from Pd to Au in Au–Pd STNFs-1.…”