Single-Atom Alloy Pd–Ag Catalyst for Selective Hydrogenation of Acrolein

Abstract

Pd–Ag alloy catalysts with very dilute amounts of Pd were synthesized. EXAFS results demonstrated that when the concentration of Pd was as low as 0.01 wt %, Pd was completely dispersed as isolated single atoms in Ag nanoparticles. The activity for the hydrogenation of acrolein was improved by the presence of these isolated Pd atoms due to the creation of sites with lower activation energy for H2 dissociation. In addition, for the same particle size, the 0.01% Pd/8% Ag alloy nanoparticles exhibited higher selectivity than their monometallic counterparts, suggesting that the Pd atom may act as a site for the favorable bonding of the acrolein molecule for facile hydrogenation of the aldehyde functionality.

Intermetallic Compounds as an Alternative to Single‐atom Alloy Catalysts: Geometric and Electronic Structures from Advanced X‐ray Spectroscopies and Computational Studies

“…This results in active sites having well‐defined and uniform local coordination environments and catalytic properties unique from the individual components. SAA catalysts have been shown to be active and selective for both the hydrogenation and dehydrogenation of various hydrocarbons and oxygenates . Several SAA's have also been reported to be resistant to poisoning by CO due to greatly reduced adsorption enthalpies on the isolated atoms compared to pure metal surfaces .…”

“…In all studies, the enhanced catalytic function has been attributed to the unique geometric and electronic properties of the isolated metal atoms. In reported SAA's, Ni, Pd, or Pt has commonly been chosen as the catalytic component while a coinage metal (i. e. Cu, Ag, Au) was selected as the host . However, mixtures of these elements typically form solid solutions where each metal is randomly distributed throughout the bulk lattice; so high host‐to‐catalyst atomic ratios are required to ensure complete isolation of active sites.…”

Single Atom Alloy Preparation and Applications in Heterogeneous Catalysis

“…At the same time, Meyer et al . prepared PdAg SAA through traditional impregnation method and evaluated its catalytic performances for acrolein hydrogenation at 200 °C. They found that sequential impregnation was more favorable for the single atom alloy formation than co‐impregnation.…”

“…SAA catalyst studies are mainly focused on their applications in hydrogenation reactions . It should be pointed out that SAA catalyst applications for dehydrogenation,[31b,31c,41] oxidation were also reported in several literatures.…”

Design of Noble Metal Electrocatalysts on an Atomic Level

“…Their excellent property towards ethanol electrooxidation reaction (EOR) benefits from exposing abundant active sites. Alternatively, adjusting the surface chemical environment by the interaction of two or multiple metals is a useful method to enhance the intrinsic activity of each site . For example, the nanoporous Au membranes with atomically thin Pd and Pt overlayer coating synthesized by Ding‘s group via an underpotential deposition process, exhibited extremely high activity for ORR .…”