Evidence of a Unique Electron Donor−Acceptor Property for Platinum Nanoparticles as Studied by XPS

Qiu, Limei; Liu, Fen; Zhao, Lei; Yang, Wensheng; Yao, Jiannian

doi:10.1021/la053071q

Cited by 193 publications

(166 citation statements)

References 14 publications

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“…63 Several studies have shown that charge transfer and the co-ordination mode of PVP molecules with noble metal nanoparticles to be size dependent. [64][65][66] The XPS data in this study also indicates that the interaction mode of PVP capping ligands is also dependent on the nature of the surface facet for Pd NCs. This finding is important for both shape selective NC synthesis with high energy faceted surfaces, suggesting that the structure and electronic interaction of the ligand is important in preserving the long term stability and structure of high energy surfaces.…”

Section: Oxidation and Interaction Of Pvp With Pd Nanocrystalsmentioning

confidence: 82%

Stability, Oxidation, and Shape Evolution of PVP-Capped Pd Nanocrystals

et al. 2014

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Access to the full text of the published version may require a subscription. Rights © 2014 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form AbstractA critical aspect in the practical application and enhanced catalytic performance of shape controlled nanocrystals is their stability and morphology retention under ambient conditions.Changes to the morphology of shape-controlled Pd nanocrystals capped by PVP are assessed by TEM and surface oxidation was evaluated by X-ray photoelectron spectroscopy (XPS), over 12 months. Surface oxidation of PVP-capped Pd nanocrystals resulted in loss of edge and corner sites and transition to spherical morphologies. The shape stability of the nanocrystals was found to follow the trend cubic < cuboctahedra < octahedral ~ concave cubes. For low index planes, {111} surfaces are more resistant to oxidation compared to {100} facets, correlating with the surface free energy of the nanocrystals. Cubic and cuboctahedral nanocrystals transitioned to spherical particles while octahedral nanocrystals retained their morphology. The presence of high energy {110} facets were observed in the cubic nanocrystals which undergo surface reconstruction. The presence of surface defects such as stacking faults were also found to influence the rate of the structural changes.Concave cubic nanocrystals, which possess high index facets and surface energies were consistently found to display excellent morphology retention. The concave cubic 2 nanocrystals displayed superior shape stability and reduced oxidation compared to cubic and cuboctahedral nanocrystals. XPS analysis further determined that PVP capping ligands on different Pd surface facets strongly influences the morphological consistency. The stability of the concave cubes can be attributed to stronger chemisorption of PVP capping ligands to the high index plane making them less susceptible to oxidation.

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Section: Oxidation and Interaction Of Pvp With Pd Nanocrystalsmentioning

confidence: 82%

Stability, Oxidation, and Shape Evolution of PVP-Capped Pd Nanocrystals

et al. 2014

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“…In addition to this, there is an additional peak for unreduced palladium at 343.24 and 337.82 eV corresponding to the 3d3/2 and 3d5/2 levels, respectively. The emergence of new peaks at higher binding energy 29 suggests that there is a charge transfer from the metal-to-polymer matrix. The analysis further reveals that 29.44% of Pd 0 is influenced by the donor-acceptor interaction; 56.40% of Pd 0 is unaffected by this interaction and the remaining 14.16% is unreduced Pd.…”

Section: Resultsmentioning

confidence: 99%

Carbon-Supported Palladium–Polypyrrole Nanocomposite for Oxygen Reduction and Its Tolerance to Methanol

Jeyabharathi

Venkateshkumar

Mathiyarasu

et al. 2010

J. Electrochem. Soc.

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Carbon-supported palladium-polypyrrole ͑Pd-PPy/C͒ nanocomposite was synthesized by oxidative polymerization of pyrrole and reduction of palladium͑II͒ precursor salt in the presence of Vulcan XC-72R. The Pd-PPy/C composites were characterized by X-ray diffraction ͑XRD͒, Fourier transform IR, X-ray photoelectron spectroscopy ͑XPS͒, thermogravimetric analysis ͑TGA͒, and transmission electron microscopy ͑TEM͒ techniques. The XRD analysis of Pd-PPy/C shows the formation of the face-centered cubic structure of Pd particles and the mean particle size calculated from TEM was 5.3 Ϯ 2.0 nm. The electrochemical stability of Pd-PPy/C was examined by cyclic voltammetry in an acid solution. The thermal stability and Pd loading in the composite was assessed using TGA. The introduction of Pd in the conducting PPy/C matrix gives better catalytic activity toward oxygen reduction with resistance to methanol oxidation. This was further elucidated by the XPS analysis showing d-band vacancy that is attributed to metal-polymer interaction. From the polarization studies, it is observed that even in the presence of methanol there is no significant cathodic shift in the half-wave potential, revealing that Pd-PPy/C is tolerant to methanol. Rotating ring disk electrode studies show that there is only a negligible quantity of hydrogen peroxide produced in the potential region where its production is expected to be high. This confirms that Pd-PPy/C catalyzes reduction of oxygen directly to water through a four-electron pathway. © 2010 The Electrochemical Society. ͓DOI: 10.1149/1.3489266͔ All rights reserved. Methanol crossover from anode to cathode poses a big challenge for the development of direct methanol fuel cells ͑DMFCs͒ because it produces a mixed potential and reduces cell performance. To circumvent this problem, considerable effort has been invested in finding novel methanol-tolerant cathode catalysts with good stability and catalytic activity for oxygen reduction. In state-of-the-art DMFCs, ͑a͒ chevral-phase-type compounds, 1,2 ͑b͒ N 4 macrocyclic complexes, 3-5 ͑c͒ bimetallic platinum and palladium based alloys involving transition metals and p-block metals, 6-13 and ͑d͒ trimetallic alloys 14,15 are reported as DMFC cathode catalysts that show methanol tolerance. In one or the other ways, these catalysts are successful to some extent in achieving the required performance. The synthesis of methanol-tolerant cathode materials with high oxygen reduction activity and stability in fuel cell operating conditions is a challenge to the commercialization of DMFCs. 16 A variety of polymer-metal systems [17][18][19][20] involving polymers such as polyaniline, polypyrrole, poly͑3,4-ethylenedioxythiophene͒, etc., and metals such as Pt, Pd, Au, etc., are known for chemical and electrocatalytic applications. Mimicking metal-porphyrin complexes using heterocyclic polymer-metal composites is one of the novel ways of finding metal-N sites, which are known for the oxygen reduction reaction ͑ORR͒ catalytic activity. 21,22 Recently, Bashyam and Zelena...

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“…In general, PtNPs are prepared via the chemical reduction of Pt 4+ ions by hydrogen [6,9], alcohols [2,5,[10][11][12][13], borohydride [14][15][16][17][18], glycol [3,6], or ethylene glycol [19,20] in the presence of a stabilizer or on a solid support (Scheme 1). Among the aforementioned reducing agents, borohydride (BH 4 -) is most suitable for minimizing the particle size because it enables rapid reduction to afford very small nuclei, whose growth is hindered.…”

Section: Introductionmentioning

confidence: 99%

High-yield synthesis of PVP-stabilized small Pt clusters by microfluidic method

et al. 2012

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Monodisperse PVP-stabilized Pt nanoparticles (PtNPs) with an average diameter of 1.4 ± 0.3 nm were efficiently produced via the complete reduction of Pt 4+ ions by BH 4 -in a micromixer.Because of microfluidic mixing, hydrolytic decomposition of BH 4 -by the PtNPs formed in the initial stage of the reaction was suppressed, and hence, the PtNP yield was higher than that in the conventional batch mixing. The results of various spectroscopic analyses including EXAFS, FTIR of CO and XPS revealed that the microfluidically synthesized PtNPs were negatively charged and had a high population of edges and vertices on their surface. The PtNPs dispersed in oxygen-saturated water catalyzed the selective oxidation of PhCH 2 OH to PhCHO. Highlights: Microfluidic method enhanced the yield of PtNPs. The PVP-stabilized PtNPs were small and monodisperse (1.4 ± 0.3 nm). The PVP-stabilized PtNPs were negatively charged. The PVP-stabilized PtNPs in water oxidized PhCH 2 OH selectively to PhCHO.

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Evidence of a Unique Electron Donor−Acceptor Property for Platinum Nanoparticles as Studied by XPS

Cited by 193 publications

References 14 publications

Stability, Oxidation, and Shape Evolution of PVP-Capped Pd Nanocrystals

Stability, Oxidation, and Shape Evolution of PVP-Capped Pd Nanocrystals

Carbon-Supported Palladium–Polypyrrole Nanocomposite for Oxygen Reduction and Its Tolerance to Methanol

High-yield synthesis of PVP-stabilized small Pt clusters by microfluidic method

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