Rh_1−xPd_xnanoparticle composition dependence in CO oxidation by oxygen: catalytic activity enhancement in bimetallic systems

Abstract

Bimetallic 15 nm Rh(1-x)Pd(x) nanoparticle catalysts of five different compositions and supported on Si wafers have been synthesized, characterized using TEM, SEM, and XPS, and studied in CO oxidation by O(2) in two pressure regimes: atmospheric pressure and 100-200 mTorr. The RhPd bimetallic nanocrystals exhibited similar synergetic effect of increased reaction activity at both atmospheric (760 Torr) and moderate (100-200 mTorr) pressures compared with pure Pd or Rh. The magnitude of the effect depends on the relative pressures of the CO and O(2) reactant gases and the reaction temperature. The catalytic activity of the nanocrystals measured at moderate pressure is directly correlated to the APXPS studies, which were carried out in the same pressure. The APXPS studies suggest that the Pd-Rh interfaces are important for the enhanced activity of the bimetallic nanoparticles.

Evolution of surface of Pd-Rh bimetallic nanocubes and its correlation with CO oxidation

“…Apparently, the activation energies of Pd Table 2). Such observation was consistent with the conclusion reported in the literature where the activation barriers of Pd x Rh 1−x NPs decreased with the increased atomic fraction of Pd [53]. On the other hand, the activation energy of the Pd 0.6 Rh 0.4 −H 2 −CO oxidation−O 2 for CO oxidation was 63 kJ mol −1 .…”

“…On the other hand, the activation energy of the Pd 0.6 Rh 0.4 −H 2 −CO oxidation−O 2 for CO oxidation was 63 kJ mol −1 . AP-XPS studies of Pd 0.6 Rh 0.4 −H 2 −CO oxidation−O 2 during CO oxidation uncovered that its active phase was RhO x loaded on PdRh bimetallic alloy [53]. This was consistent with the reports where the active RhO x was the active phase of Rh NPs with a size ≤ 2.5 nm [48,55], in which the activation barrier of RhO x was reported at ca.…”

“…The in-situ XPS study showed that the active surface phases of the as-synthesized pure Pd NCs and Rh NCs to CO oxidation were metallic Pd and metallic Rh, respectively. The activation energies of metallic Pd and Rh for CO oxidation reaction were in qualitative agreement with the values reported in literatures [52][53][54].…”

Synthesis, catalysis, surface chemistry and structure of bimetallic nanocatalysts

“…1 Bimetallic materials are important catalysts due to their numerous advantages. [2][3][4][5][6][7] For example, composition (at large scale), coordination environment of the metal atom (on the atomic scale), and electronic state of the parent metal can be tuned systematically due to the spectacular success in the synthesis of bimetallic nanoparticles in the recent decade. [8][9][10][11][12][13] As heterogeneous catalysis is performed on the surface of a catalyst, the surface structure and chemistry of a bimetallic catalyst in term of geometric and electronic structures of metal atoms on the surface are the most important parameters which determine the catalytic performance of a bimetallic catalyst.…”

Synthesis, Characterization and Synthetic Applications of Fly-ash:H3PO4 Nanocatalyst

“…Neodymium oxide (Nd2O3) nanocatalyst was used for studying the surface activity of SERS substrates [33]. Some nanomaterials are used as efficient catalysts for CO oxidation [34], [35], as electrochemical redox systems [36], for hydrogenation [37], for functional-thiolate stabilization [38] and fullerene-substituted oligopyridine. Recently Sujitha and Kannan [39] synthesized and characterized green gold nanoparticles using citrus fruit (Citrus limon, Citrus reticulata and Citrus sinensis) aqueous extract.…”