Cu/Pd alloys

Bimetallic (98) and alloy catalysts (97), of interest for hydrogenation reactions, have been investigated in in situ characterizations of methanol synthesis from CO and H2 in the presence of novel Cu-Pd alloy catalysts supported on carbon the results show surface segregation of palladium on the catalyst particles in CO atmospheres, but surfaces with equal amounts of copper and palladium when the atmosphere is H2 (97). 

Cu-Pd alloy system structure, phase stability and catalysis... 

Fig. 13. Concentration profiles for the CusPd alloy at different temperatures (300-700 K) in different Monte Ccfflo simulations [40]. (a) Simulation set SI (b) simulation set S2. The EAM parameters used were optimized specifically for the Cu-Pd alloy.

The stability of such intermediates can be strongly affected by alloying and recent work with Cu/Pd alloys referred to above, has shown destabilisation of the formate by the influence of Pd which is not present in the top layer, but is in the second layer (Newton et al., 1991,1992). 

Another striking example of the decisive role of the mode of preparation may be found in the behavior of Cu-Pd alloys [Rienacker et al. (65)] (see Fig. 18). When copper is alloyed with palladium the activation energy remains practically constant up to 65% Pd on further addition of Pd, E falls rapidly down to the low value of Pd. This is only true, however, for normally prepared, disordered alloys. If, by tempering, the so-called ordered alloys are prepared, in which the Pd-atoms have definite crystallographic positions, the result is essentially different (see Fig. 18) now the activation energy of the alloys is nearly additively composed of the contributions of the components in the alloy. Analogous results were obtained for the system Cu-Pt [Rienacker (69)]. 

Fig. 18. Dehydrogenation of formic acid on Cu-Pd alloys, according to Rienacker, Wcssing, and Trautrnarm (6S) (Cu and Pd form a continuous scries of solid solutions). O—disordered alloys X—ordered alloys.

Van Dijk MA, Tchebotareva AL, Orrit M, Lippitz M, Berciaud S, Lasne D, Cognet L, Lounis B (2006) Absorption and scattering microscopy of single metal nanoparticles. Phys Chem Chem Phys 8 3486-3495 Vasan HN, Rao CNR (1995) Nanoscale Ag-Pd and Cu-Pd alloys. J Mater Chem 5 1755-1757 Walter EC, Ng K, Zach MP, Penner RM, Favier F (2002a) Electronic devices from electrodeposited metal nanowires. Microelectron Eng 61-62 555-561... 

Fig. 20.4 ZPS-purified a valence DOS showing the charge flow directions upon Ag/Pd and Cu/ Pd alloy formation [47] and b core-level DOS of Pt and Rh adatoms [48]. Results suggest that AgPd alloy and Rh adatoms serve as donor-type catalysts because of the polarization awhile Pt adatoms and CuPd alloy as acceptor-type catalysts because of the dominance of quantum...

Figure 19. Density of states (DOS) calculated for crystals in the bulk (—) and polyhedron at a grain boundary (—) in (a) Ni,Si and (b) Cu,Pd alloys, respectively (Reproduced by permission of the American Physical Society from Eberhart and Vvedenski, 1986)...

G.L.W., and Muller, S. (2009) Stability and instability of long-period superstmctures in binary Cu-Pd alloys a first principles study. Acta Mater., 57, 1660. 

Fig. 16. AuCu3 antiphase domain structure in Cu3Pd alloys. Curves for electron-atom ratio versus domain size M are derived from the equation given in the text. Points show experimental data determined for Cu-Pd alloys. The electron concentration is calculated on the assumption that Pd contributes no electrons. After Sato and Toth.<22 ...

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