Bimetallic palladium catalysts: influence of the co-metal on the catalyst performance

Sites for the selective hydrogenation of ethyne to ethene on supported NiO/Au catalysts

“…It was proposed that the Au component served to adsorb and activate the C-Cl bond whereas the H 2 dissociated at the Ni 0 . The addition of tin to the Pt/SiO 2 catalyst produced a remarkable positive shift in both the product distribution and TOF in the liquid-phase hydrogenation of unsaturated aldehyde to corresponding alcohols [43,44]. The simultaneous increase in both activity and selectivity indicates the formation of a new type of mixed (M x+ )/(Pt) 0 clusters, different in nature when Our investigations of model Au, Ni/Au, and Ni catalysts by XPS, DRIFT, and XAS techniques showed that nickel in both Ni/Au and Ni catalysts exists as NiO, gold in the Au catalyst exists as Au 0 nanoclusters, whereas the Au 0 nanoclusters co-exist with Au 3+ cations in the NiO/Au samples [7].…”

Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts

“…EXAFS characterization on different co-precipitated Pd/Fe 2 O 3 catalysts has been deeply investigated by the research group of Prof. Tsang [109,[131][132][133][134]. The motivation beyond the use of EXAFS spectroscopy needs to be found in the necessity to define both the dimension of Pd nanoparticles (too small to be accurately detected by classic XRD and TEM analysis) as well as to confirm the presence of Pd-Fe bimetallic clusters on the catalyst surface (as suggested by XPS measurements).…”

“…With respect to other PGM elements, palladium is characterized by a fundamental electronic configuration unique among transition metals (4d 10 , 5s 0 ) [107] that can be strongly influenced by the coordination environment [108]. The modification of catalytic properties of palladium by adding a second metal can be related, from a general point of view, in terms of (i) "ligand" effects (related to shifting of the d-band density); (ii) "ensemble" effect (a dilution of palladium surface by a relatively unreactive second co-metal); (iii) "stabilizing" effect (improving the active sites stability) [109][110][111][112][113][114]. Hence, heterogeneous catalysts based on palladium bimetallic systems have gained increasing attention for their enhanced activity and durability in different reactions .…”

Recent Advances in the Liquid‐Phase Synthesis of Metal Nanostructures with Controlled Shape and Size for Catalysis

“…According to the Sabatier's principle, an intermediate formed by a reactant at the surface must be stable enough to be formed, but not too stable since it must decompose yielding the products. Geometric (''ensemble'') effect implies that the reactant needs for adsorption sometimes multiple atoms with a specific arrangement (18,106). Structure sensitivity of a variety of the reactions was first studied using model catalysts, which were single metal crystals.…”

“…This phase was claimed to be responsible for the direct alkyne hydrogenation to alkane (106), while some reports did not find this detrimental effect (18,119). In addition, this phase often can hardly be stable under the reaction conditions: the partial pressure of hydrogen necessary to obtain a stable bPdH phase during the reaction has to be one order of magnitude higher than the equilibrium pressure of hydrogen above the b-PdH phase at the same temperature (116).…”