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Title: Potential of ZrO clusters as replacement Pd catalyst

Abstract

Atomic clusters with specific size and composition and mimicking the chemistry of elements in the periodic table are commonly known as superatoms. It has been suggested that superatoms could be used to replace elements that are either scarce or expensive. Based on a photoelectron spectroscopy experiment of negatively charged ions, Castleman and co-workers [Proc. Natl. Acad. Sci. U.S.A. 107, 975 (2010)] have recently shown that atoms of Ni, Pd, and Pt which are well known for their catalytic properties, have the same electronic structure as their counterpart isovalent diatomic species, TiO, ZrO, and WC, respectively. Based on this similarity they have suggested that ZrO, for example, could be a replacement catalyst for Pd. Since catalysts are seldom single isolated atoms, one has to demonstrate that clusters of ZrO also have the same electronic structure as same sized Pd clusters. To examine if this is indeed the case, we have calculated the geometries, electronic structure, electron affinity, ionization potential, and hardness of Pd{sub n} and (ZrO){sub n} clusters (n = 1-5). We further studied the reaction of these clusters in neutral and charged forms with H{sub 2}, O{sub 2}, and CO and found it to be qualitatively different in most cases.more » These results obtained using density functional theory with hybrid B3LYP functional do not support the view that ZrO clusters can replace Pd as a catalyst.« less

Authors:
; ;  [1];  [2]
  1. Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)
  2. Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, USA and Department of Chemistry, Stanford University, Stanford, California 94305 (United States)
Publication Date:
OSTI Identifier:
22419888
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ATOMIC CLUSTERS; ATOMS; CARBON MONOXIDE; CATALYSTS; DENSITY FUNCTIONAL METHOD; ELECTRONIC STRUCTURE; HARDNESS; IONIZATION POTENTIAL; IONS; PERIODIC SYSTEM; PHOTOELECTRON SPECTROSCOPY; TITANIUM OXIDES; TUNGSTEN CARBIDES; ZIRCONIUM OXIDES

Citation Formats

Behera, Swayamprabha, King, Nicholas, Jena, Puru, E-mail: pjena@vcu.edu, and Samanta, Devleena. Potential of ZrO clusters as replacement Pd catalyst. United States: N. p., 2014. Web. doi:10.1063/1.4887086.
Behera, Swayamprabha, King, Nicholas, Jena, Puru, E-mail: pjena@vcu.edu, & Samanta, Devleena. Potential of ZrO clusters as replacement Pd catalyst. United States. doi:10.1063/1.4887086.
Behera, Swayamprabha, King, Nicholas, Jena, Puru, E-mail: pjena@vcu.edu, and Samanta, Devleena. Mon . "Potential of ZrO clusters as replacement Pd catalyst". United States. doi:10.1063/1.4887086.
@article{osti_22419888,
title = {Potential of ZrO clusters as replacement Pd catalyst},
author = {Behera, Swayamprabha and King, Nicholas and Jena, Puru, E-mail: pjena@vcu.edu and Samanta, Devleena},
abstractNote = {Atomic clusters with specific size and composition and mimicking the chemistry of elements in the periodic table are commonly known as superatoms. It has been suggested that superatoms could be used to replace elements that are either scarce or expensive. Based on a photoelectron spectroscopy experiment of negatively charged ions, Castleman and co-workers [Proc. Natl. Acad. Sci. U.S.A. 107, 975 (2010)] have recently shown that atoms of Ni, Pd, and Pt which are well known for their catalytic properties, have the same electronic structure as their counterpart isovalent diatomic species, TiO, ZrO, and WC, respectively. Based on this similarity they have suggested that ZrO, for example, could be a replacement catalyst for Pd. Since catalysts are seldom single isolated atoms, one has to demonstrate that clusters of ZrO also have the same electronic structure as same sized Pd clusters. To examine if this is indeed the case, we have calculated the geometries, electronic structure, electron affinity, ionization potential, and hardness of Pd{sub n} and (ZrO){sub n} clusters (n = 1-5). We further studied the reaction of these clusters in neutral and charged forms with H{sub 2}, O{sub 2}, and CO and found it to be qualitatively different in most cases. These results obtained using density functional theory with hybrid B3LYP functional do not support the view that ZrO clusters can replace Pd as a catalyst.},
doi = {10.1063/1.4887086},
journal = {Journal of Chemical Physics},
number = 3,
volume = 141,
place = {United States},
year = {Mon Jul 21 00:00:00 EDT 2014},
month = {Mon Jul 21 00:00:00 EDT 2014}
}
  • The H-H interaction potential in Pd{sub {ital x}}H{sub 2} ({ital x}=2,4) clusters is investigated by means of {ital ab} {ital initio} Hartree-Fock techniques. Both linear arrangements and spatial configurations, in which the H-H bond is taken perpendicular to the line, or plane, of the Pd atoms, are considered. The Pd-Pd distances are kept fixed while the H-H potential-energy curves are calculated. Only the linear geometry allows a reduction of the H-H distance with respect to the gas phase. Fusion rates are calculated for the latter geometry. Our results show that, even for the unrealistic situation in which the two Hmore » atoms are in between two Pd atoms at the shortest distance found in the metal (5.2 a.u.), the fusion rate (10{sup {minus}56}) is far below the values inferred by some authors from experimental data.« less
  • The crystal structure of partially Pd{sup 2+}-exchanged zeolite X, dehydrated at 400 C in a flowing O{sub 2} stream (a = 24.982(4){angstrom}), has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd{bar 3} at 21(1) C. The crystal was first Pd{sup 2+}-exchanged in a flowing stream of 0.05 M aqueous Pd(NH{sub 3}){sub 4}Cl{sub 2} for 3 days. After dehydration at 400 C in flowing oxygen, the crystal was evacuated at 21(1) C and 2 x 10{sup {minus}6} Torr for 2 h. The structure was refined to the final error indices R{sub 1} = 0.070 and R{submore » 2} = 0.051 for the 196 reflections for which I > 2{sigma}(I). In this structure, Pd{sup 2+} ions are found at four crystallographic sites: Na{sup +} ions fill just one, and nonframework oxygens are found at two. Eight Pd{sup 2+} ions and eight O{sup 2{minus}} ions fill the 16 double six-oxygen ring (D6R) centers (site I) per unit cell; this interpretation of the electron density at site I behaves well in least-squares refinement. Each of these Pd{sup 2+} ions is octahedrally coordinated by framework oxygens. Sixteen Pd{sup 4+} ions at site I{prime} (Pd-O = 2.103(13){angstrom}) lie in six-ring planes. With the eight oxide ions at site I at central positions and 16 more terminal, they form eight linear O-Pd-O-Pd-O clusters along 3-fold axes per unit cell. Each passes through the center of a D6R and extends into its two adjacent sodalite cavities. Considering bond lengths and charge balance, it is proposed that they are [HO-Pd{sup IV}-O-Pd{sup IV}-OH]{sup 4+} clusters with O-Pd-O-Pd-O linear. Thirty-two Na{sup +} ions fill site II and are recessed 1.03(1){angstrom} into the supercage from the single six-ring plane (Na-O = 2.258(11){angstrom}). About two Pd{sup 2+} ions at another site I{prime} (Pd-O = 2.371(11){angstrom}) are displaced 1.11 {angstrom} from six-ring plane into sodalite cages. About four Pd{sup 2+} ions lie at site III{prime} in the supercage (Pd-O = 2.16(5){angstrom}).« less
  • [Pd{sub 16}Ni{sub 4}(CO){sub 22}(PPh{sub 3}){sub 4}]{sup 2-} (1) and [Pd{sub 33}Ni{sub 9}(CO){sub 41}(PPh{sub 3}){sub 6}]{sup 4-} (2) were obtained as the two major products from the reduction of PdCl{sub 2}(PPh{sub 3}){sub 2} with [Ni{sub 6}(CO){sub 12}]{sup 2-}. Their crystal structures as [PPh{sub 4}]{sup +} salts were unambiguously determined from CCD X-ray crystallographic analyses; the resulting stoichiometries were ascertained from elemental analyses. Infrared, multinuclear {sup 1}H, {sup 31}P{l_brace}{sup 1}H{r_brace} NMR, UVvis, CV, variable-temperature magnetic susceptibility, and ESI FT/ICR mass spectrometric measurements were performed. The Pd{sub 16}Ni{sub 4} core of 1 ideally conforms to a ccp {nu}{sub 3} tetrahedron of pseudo-T{sub d}more » ({sub {ovr 4}}3m) symmetry. Its geometry normal to each tetrahedral Pd7Ni3 face (i.e., along each of the four 3-fold axes) may be viewed as a four-layer stacking of 20 metal atoms in a ccp [a(Ni{sub 1}) b(Pd{sub 3}) c(Pd{sub 6}) a(Pd{sub 7}Ni{sub 3})] sequence. A comparative analysis of the different ligand connectivities about the analogous metal-core geometries in 1 and the previously reported [Os{sub 20}(CO){sub 40}]{sup 2-} has stereochemical implications pertaining to the different possible modes of carbon monoxide attachment to ccp metal(111) surfaces. The unique geometry of the Pd{sub 33}Ni{sub 9} core of 2, which has pseudo-D{sub 3h} ({sub {ovr 6}}2m) symmetry, consists of five equilateral triangular layers that are stacked in a hcp [a(Pd{sub 7}Ni{sub 3}) b(Pd{sub 6}) a(Pd{sub 7}Ni{sub 3}) b(Pd{sub 6}) a(Pd{sub 7}Ni{sub 3})] sequence. Variable-temperature magnetic susceptibility measurements indicated both 1 and 2 to be diamagnetic over the entire temperature range from 5.0 to 300 K. Neutral Pd{sub 12}(CO){sub 12}(PPh{sub 3}){sub 6} (3) and [Pd{sub 29}(CO){sub 28}(PPh{sub 3}){sub 7}]{sup 2-} (4) as the [PPh{sub 4}]{sup +} salt were obtained as minor decomposition products from protonation reactions of 1 and 2, respectively, with acetic acid. Compound 3 of pseudo-D{sub 3d} ({sub {ovr 3}}2/m) symmetry represents the second highly deformed hexacapped octahedral member of the previously established homopalladium family of clusters containing uncapped, monocapped, bicapped, and tetracapped Pd6 octahedra. The unprecedented centered 28-atom polyhedron for the Pd{sub 29} core of 4 of pseudo-C{sub 3v} (3m) symmetry may be described as a four-layer stacking of 29 metal atoms in a mixed hcp/ccp [a(Pd{sub 1}) b(Pd{sub 3}) a(Pd{sub 10}) c(Pd{sub 15})] sequence.« less
  • Bimetallic nanostructures with non-random metal atoms distribution are very important for various applications. To synthesize such structures via benign wet chemistry approach remains challenging. This paper reports a synthesis of a Au/Pd alloy nanostructure through the galvanic replacement reaction between Pd ultrathin nanowires (2.4 {+-} 0.2 nm in width, over 30 nm in length) and AuCl3 in toluene. Both morphological and structural changes were monitored during the reaction up to 10 h. Continuous changes of chemical composition and crystalline structure from Pd nanowires to Pd68Au32 and Pd45Au55 alloys, and to Au nanoparticles were observed. More interestingly, by using combined techniquesmore » such as high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDS), UV-vis absorption, and extended X-ray absorption fine structure (EXAFS) spectroscopy, we found the formation of Pd68Au32 non-random alloy with Au-rich core and Pd-rich shell, and random Pd45Au55 alloy with uniformly mixed Pd and Au atom inside the nanoparticles, respectively. Density functional theory (DFT) calculations indicated that alkylamine will strongly stabilize Pd to the surface, resulting in diffusion of Au atoms into the core region to form a non-random alloy. We believe such benign synthetic techniques can also enable the large scale preparation of various types of non-random alloys for several technically important catalysis applications.« less