Platinum Monolayer Electrocatalysts for the Oxygen Reduction Reaction: Improvements Induced by Surface and Subsurface Modifications of Cores

Cai, Yun; Adžić, Radoslav R.

doi:10.1155/2011/530397

Cited by 32 publications

(19 citation statements)

References 76 publications

(97 reference statements)

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“…It has been long known that there is a volcano-shaped relationship between the ORR activity and the d-band center of transition metals where Pt lies nearest the top of the volcano [17,59,60]. To reach the peak performance, it has been argued that the d-band center of Pt needs to be downshifted by 0.1 -0.2 eV so as to weaken the interactions with oxygen intermediates [61]. In fact, in a prior study [37], we observed that the ORR activity of Pt/GQD nanocomposites reached the maximum with about 20% structural defects of the GQDs.…”

Section: Resultsmentioning

confidence: 99%

Oxygen reduction catalyzed by nanocomposites based on graphene quantum dots-supported copper nanoparticles

Liu

Yang

Chen

2016

International Journal of Hydrogen Energy

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Nanocomposites based on graphene quantum dots (GQDs)-supported copper nanoparticles were prepared by thermal refluxing of copper salts in 1,2-propanediol at 140 °C in the presence of GQDs. Transmission electron microscopic measurements showed that the resulting Cu/GQD nanoparticles increased from 5 to 15 nm in average diameter with increasing metal loadings. Raman spectroscopic measurements showed that all nanocomposites exhibited well-defined D and G vibrational bands. X-ray photoelectron spectroscopic studies indicated the formation of Cu 2 O and CuO in the nanocomposite particles, along with various defect concentrations within the GQD graphitic skeletons. Electrochemical studies showed that the nanocomposites exhibited apparent electrocatalytic activity in oxygen reduction in alkaline media, and the sample with a Cu/C atomic ratio of 2.88% exhibited the best ORR activity among the series, within the context of onset potential, number of electron transfer and kinetic current density. The performance was further improved by deliberate hydrothermal treatments of the sample, and 160 °C was identified as the optimal temperature, which was ascribed to manipulation of the electronic interactions between copper nanoparticles and oxygen intermediates by the GQD structural defects.

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Section: Resultsmentioning

confidence: 99%

Oxygen reduction catalyzed by nanocomposites based on graphene quantum dots-supported copper nanoparticles

Liu

Yang

Chen

2016

International Journal of Hydrogen Energy

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“…The most extensive and successful work in the field is due to Adzic and co-workers, who prepared finely tuned Pt monolayer catalysts with very high ORR intrinsic catalytic activity and the highest reported mass specific activity [65,66,79,[81][82][83]86,[88][89][90][91][92]96,[163][164][165][166][167][168][169][170][171][172][173][174][175][176][177][178][179][180]. In more detail, they have predicted theoretically (by means of Density Functional Theory (DFT) calculations) and confirmed experimentally that the most active catalyst for ORR is based on a Pt skin and a Pd-based core [81] which can be further improved by the use of a mixed Pt-noble metal skin and can reach an enhancement of mass activity in the 3-20-fold range [82].…”

Section: Oxygen Reductionmentioning

confidence: 99%

Electrocatalysts Prepared by Galvanic Replacement

et al. 2017

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Galvanic replacement is the spontaneous replacement of surface layers of a metal, M, by a more noble metal, M noble , when the former is treated with a solution containing the latter in ionic form, according to the general replacement reaction: nM + mM noble n+ → nM m+ + mM noble. The reaction is driven by the difference in the equilibrium potential of the two metal/metal ion redox couples and, to avoid parasitic cathodic processes such as oxygen reduction and (in some cases) hydrogen evolution too, both oxygen levels and the pH must be optimized. The resulting bimetallic material can in principle have a M noble-rich shell and M-rich core (denoted as M noble (M)) leading to a possible decrease in noble metal loading and the modification of its properties by the underlying metal M. This paper reviews a number of bimetallic or ternary electrocatalytic materials prepared by galvanic replacement for fuel cell, electrolysis and electrosynthesis reactions. These include oxygen reduction, methanol, formic acid and ethanol oxidation, hydrogen evolution and oxidation, oxygen evolution, borohydride oxidation, and halide reduction. Methods for depositing the precursor metal M on the support material (electrodeposition, electroless deposition, photodeposition) as well as the various options for the support are also reviewed. 1. Principle of Galvanic Replacement/Deposition 1.1. Thermodynamic Considerations When a metal, M (e.g., Cu, Fe, Co, Ni, Al, etc.), is immersed in a solution containing ions of a more noble metal, M noble n+ (e.g., Pt, Au, Pd, Ag, Ru, Ir, Rh, Os, etc.-i.e., a metal with a higher standard potential) then, due to the difference in their standard electrochemical potentials, E 0 noble − E 0 > 0, and provided that the ionic form of M is stable under the given experimental conditions (of temperatue, pH, complexing agents etc.), the following reaction is thermodynamically favored and can take place spontaneously: M noble n+ + n/m M → M noble + n/m M m+ (1) This reaction, which bears similarities with transmetalation reactions between metal complexes [1] and is also known as immersion plating [2] in the plating industry and galvanic replacement [3] in materials chemistry, can be considered to originate from the coupling of the following two half-reactions: M noble n+ + ne − ↔ M noble (E 0 noble) (2) M m+ + me − ↔ M (E 0) (3)

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“…Das Pt 80 Pd 20 -Aerogel zeigt die hçchste massenspezifische Aktivität, die fünfmal hçher ist als jene des kommerziellen Pt/C-Katalysators.D ie Absenkung des d-Bandzentrums in den Legierungen, die häufig als ein Deskriptor des elektronischen Oberflächenzustands von ORR-Katalysatoren verwendet wird, zeigt das gleiche vulkanfçrmige Verhalten in den Pt n Pd 100Àn -Aerogelen. [112][113][114][115][116] Te sts der Alterungsbeständigkeit zufolge zeigen die bimetallischen Aerogele eine viel bessere Langzeitstabilitätals reine Pt-und Pd-Aerogele sowie Pt/C. Ein anderer interessanter Ansatz zur Herstellung hocheffizienter Elektrokatalysatoren ist die Bildung hohler Gelstrukturen aus vorab gebildeten, massiven Gelnetzwerken durch galvanischen Austausch.…”

Section: Metallaerogele -Ein Riesiger Entwicklungssprung Fürdie Elektunclassified

Moderne Anorganische Aerogele

et al. 2017

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Der Begriff Aerogel beschreibt im Wesentlichen eine besondere geometrische Struktur der Materie, die materialunabhängig ist und keinem speziellen Syntheseverfahren unterliegt. Grundsätzlich können daher Aerogele aus unzähligen Materialien bestehen, wodurch die Anwendungsmöglichkeiten nahezu unbegrenzt sind. Dasselbe trifft auf Nanopartikel zu. Diese werden ebenso durch ihre geometrischen Eigenschaften definiert. In den letzten Jahrzehnten standen daher nanoskalige Materialien im Fokus der Forschung, und es entwickelten sich mögliche Anwendungen in vielen naturwissenschaftlichen Bereichen. Heute ist eine Vielzahl an Metall‐, Halbleiter‐, Oxid‐ und anderen Nanopartikeln durch kolloidale Synthesen zugänglich. Dennoch ist es für eine Anwendung oft notwendig, dass diese Materialien zuvor in makroskopische Strukturen angeordnet werden. Dieser Aufsatz gibt eine ausführliche Übersicht über die Entwicklung, die die Welt der kolloidalen Nanopartikel und der Aerogele miteinander vereint. Ermöglicht wurde dies durch die kontrollierte Destabilisierung der vorab gebildeten Nanopartikel, die zu einer Anordnung der Nanopartikel zu einem dreidimensionalen, makroskopischen Netzwerk führt. Dieses revolutionäre Konzept verleiht die Möglichkeit, präzise kontrollierte Nanopartikel als Grundbausteine für makroskopische, poröse Strukturen mit einstellbaren Eigenschaften zu nutzen.

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Platinum Monolayer Electrocatalysts for the Oxygen Reduction Reaction: Improvements Induced by Surface and Subsurface Modifications of Cores

Cited by 32 publications

References 76 publications

Oxygen reduction catalyzed by nanocomposites based on graphene quantum dots-supported copper nanoparticles

Oxygen reduction catalyzed by nanocomposites based on graphene quantum dots-supported copper nanoparticles

Electrocatalysts Prepared by Galvanic Replacement

Moderne Anorganische Aerogele

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