Outstanding Catalytic Activity of Ultra‐Pure Platinum Nanoparticles

Januszewska, Aneta; Dercz, Grzegorz; Piwowar, Justyna; Jurczakowski, Rafał; Lewera, Adam

doi:10.1002/chem.201303185

Cited by 13 publications

(12 citation statements)

References 53 publications

(62 reference statements)

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“…19 In preparation of thin Pd layer underpotential deposition (UPD) of Pd on Pt was used. First palladium was reduced on Pt nanoparticles from 1 mM PdCl 2 + 2−5 mM HCl + 0.5 M H 2 SO 4 solution to determine the onset of normal palladium reduction on platinum, which was between +0.74 and +0.77 V vs RHE.…”

Section: ■ Methodsmentioning

confidence: 99%

Probing the Limits of d-Band Center Theory: Electronic and Electrocatalytic Properties of Pd-Shell–Pt-Core Nanoparticles

2015

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Theoretical DFT calculations suggest that chemisorption energy, activation barrier, and energy of dissociation of small molecules on metal surface can be correlated to the d-band center of gravity of that metal. This holds true for many systems and reactions, but there are also reports where significant discrepancies were found. Here we present the critical assessment of applicability of the d-band center theory to nonuniform catalytic systems, such as core−shell nanoparticles. For Pt-core−Pd-shell nanoparticles we found a significant enhancement of catalytic activity toward formic acid oxidation, which was assigned to observed changes of density of states close to the Fermi level, in general in agreement with d-band center theory. However, at the same time the changes in dband center for Pt-core−Pd-shell nanoparticles were contrary to those predicted by theory due to incorporation of Pt valence electrons to the overall band structure, which shifted the d-band center in the direction opposite to that predicted by the theory. Our data stress the role of experimental determination of electronic properties of catalytic systems when explaining the observed catalytic activity, as real systems can be more complicated than the one used for theoretical calculations. As a result the changes in d-band center energy must be used with care for explanation of the observed changes in catalytic activity. We show that for nonuniform systems density of states close to the Fermi level is a better predictor of chemisorption strength and catalytic activity than the d-band center. ■ INTRODUCTIONEstablishing the relationship between surface electronic structure and its catalytic activity would revolutionize many branches of science and technology. Among many fundamental studies contributing to better understanding how the electronic properties influence the catalytic activity, one of the most spectacular is the d-band center theory, developed by Norskov and co-workers, correlating the energy of the d-band center of gravity (ε d ) of the metal catalyst to the adsorption energy, activation energy, and dissociation energy of small molecules. 1−3 According to that theory the electron density of states (DOS) close to the Fermi level is correlated to the adsorbate− substrate adsorption energy due to interactions between electrons occupying d-type orbitals of the metal (d-band) and those of the adsorbate. As a result modifying the d-band DOS (d-DOS) should influence the adsorption strength and catalytic activity of the metal surface. To reflect the electronic properties of the d-band (d-DOS) ε d was proposed. According to d-band center theory, ε d can be altered, i.e., as a result of lattice strain. Changing the lattice parameters influences the degree of overlapping between d orbitals forming a d-band in metal and as a result causing narrowing or widening of the d-band and shifting ε d toward or away from the Fermi level. 1−3 There have been significant efforts to verify the d-band center theory. The effect of lattice strain on the d-ba...

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Section: ■ Methodsmentioning

confidence: 99%

Probing the Limits of d-Band Center Theory: Electronic and Electrocatalytic Properties of Pd-Shell–Pt-Core Nanoparticles

2015

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“…A significant number of studies have been dedicated to improve the activity of polycrystalline Pt by increasing the surface to mass ratio and by preparing Pt based alloys and/or core-shell nanostructures [1][2][3][4][5][6]. More recently, new synthesis methods have allowed the preparation of preferentially oriented Pt nanoparticles and thin films without the use of organic surfactants, either via electrodeposition [7,8], the polyol method [9] or cathodic corrosion [10], resulting in materials with both specifically oriented and clean surfaces, while keeping interesting surface to mass ratio. As most electrochemical reactions are well known to be structure sensitive [11], these new preparation methods allow for the preparation of Pt catalysts with specific surface structures tuned for the desired reactions.…”

Section: Introductionmentioning

confidence: 99%

Preferentially (100) oriented Pt thin film with less than a monolayer of Bi, Pd and Sb adatoms: application for formic acid oxidation

Bertin

Fleury

Roy

et al. 2015

Electrochimica Acta

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“…DEMS (electrochemical) experiments were performed in pure supporting electrolyte (0.5M H2SO4) without any cleaning step ( Fig. 4), as high purity of the nanoparticles was warranted by the synthesis procedure used [19] and was checked using XPS (Fig. 2) as described above.…”

Section: Resultsmentioning

confidence: 99%

“…N5.0 Argon and He BIP Plus (N6.7), by Air Products were used for electrolyte deaeration and as a carrier gas for DEMS experiment, respectively. Unsupported Pt, Rh and Pt-Rh nanoparticles were synthesized utilizing modified polyol method, as we described elsewhere [19], using RhCl3 (Alfa Aesar) and K2PtCl4 (Alfa Aesar) as precursors in required molar ratio, and ethylene glycol (ACS grade, Fluka) as a reducing agent.…”

Section: Methodsmentioning

confidence: 99%

On the Lack of Beneficial Role of Rh Towards C-C Bond Cleavage During Low Temperature Ethanol Electrooxidation on Pt-Rh Nanoalloys

Piwowar¹,

Lewera²

2018

Preprint

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Numerous reports in scientific literature claim the increased activity of Rh-containing systems towards C-C bond scission in electrocatalytic oxidation of ethanol at ambient temperatures. Due to the claimed C-C bond breaking ability, Rh-containing systems are intensively investigated and widely recognized as the most promising candidates as anode materials for ethanol-feed low temperature fuel cells. This study aims at verifying the claim of beneficial role of Rh towards C-C bond scission during low temperature ethanol electrooxidation on Pt-Rh nanoparticles. We determined that the surface-normalized amounts of CO 2 produced during ethanol oxidation are comparable on Pt, Rh and Pt-Rh nanoalloys, and smaller than CO 2 amounts obtained on exactly the same electrode from oxidation of monolayer of adsorbed CO. The whole amount of CO 2 detected during ethanol oxidation, regardless of Rh presence, or lack of thereof, seems to come exclusively from oxidation of submonolayer of CO ads produced during dissociative adsorption of ethanol at low electrode potential, and its subsequent oxidation at sufficiently high electrode potential. Our work suggest that Rh-containing alloys are not more active towards C-C bond scission than pure Pt, and on both metals the mechanism of oxidation of ethanol to CO 2 proceeds via the submonolayer of CO ads , which limits the quantity of CO 2 produced from ethanol at room temperature to negligible amount. The higher activity of Rh-containing materials towards C-C bond scission claimed in literature was determined to be due to overinterpretation of selectivity data.

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Outstanding Catalytic Activity of Ultra‐Pure Platinum Nanoparticles

Cited by 13 publications

References 53 publications

Probing the Limits of d-Band Center Theory: Electronic and Electrocatalytic Properties of Pd-Shell–Pt-Core Nanoparticles

Probing the Limits of d-Band Center Theory: Electronic and Electrocatalytic Properties of Pd-Shell–Pt-Core Nanoparticles

Preferentially (100) oriented Pt thin film with less than a monolayer of Bi, Pd and Sb adatoms: application for formic acid oxidation

On the Lack of Beneficial Role of Rh Towards C-C Bond Cleavage During Low Temperature Ethanol Electrooxidation on Pt-Rh Nanoalloys

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