Origin of Oxygen Reduction Reaction Activity on “Pt<sub>3</sub>Co” Nanoparticles: Atomically Resolved Chemical Compositions and Structures

Chen, Shuo; Sheng, Wenchao; Yabuuchi, Naoaki; Ferreira, Paulo J.; Allard, Lawrence F.; Shao‐Horn, Yang

doi:10.1021/jp807143e

Cited by 286 publications

(351 citation statements)

References 93 publications

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“…54 The same dependence of Co content on particle size has also been observed for acid-treated Pt 3 Co nanoparticles. 55 All of the cycled samples showed lower Co contents than the starting powder sample at any given particle diameter, agreeing with the XRF data which show overall loss of Co after cycling. The EDS data for all the samples, with the exception of those of MEA square, were best fit with an asymptotic exponential function.…”

Section: Resultssupporting

confidence: 88%

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt₃Co Catalyst Degradation in Aqueous and Fuel Cell Environments

Gilbert

Kropf

Kariuki

et al. 2015

J. Electrochem. Soc.

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Platinum-cobalt alloy nanoparticles are of great interest as cathode catalysts for PEMFCs as they have been shown to have enhanced activity versus platinum. However, their relative stability against loss of electrochemically-active surface area in relation to Pt catalysts is still debated. In this study, the evolutions of Pt 3 Co particle size distributions (PSDs) in fuel cell and aqueous environments were followed during accelerated stress tests (ASTs) using in-operando ASAXS. The measured evolutions showed a degradation mechanism dominated by loss of particles smaller than the critical particle diameter (<5.2 to 6.1 nm, CPD), which depended on environment and the AST. These evolutions were compared to that of a Pt catalyst with a similar initial PSD, which was found to have a lower degradation rate than Pt 3 Co. The ASAXS data, as well as data from aqueous dissolution, X-ray absorption spectroscopy, individual particle energy-dispersive spectroscopy, X-ray fluorescence spectrometry, and kinetic Monte Carlo calculations support a loss mechanism of increased Pt dissolution from Pt 3 Co versus Pt due to destabilization caused by extensive dealloying of particles <∼5 nm during ASTs. Polymer electrolyte fuel cells (PEFCs) are a promising highefficiency energy conversion technology suitable for mobile and stationary applications. Two of the major issues still needing to be addressed for large-scale adoption are cost and durability. The major contributing factor to these issues is the electrocatalyst needed for the cathodic oxygen reduction reaction (ORR). Pt has been shown to be the best monometallic catalyst material for ORR 1 with high activity and good stability in the acidic environment of the PEFC.2,3 However, there is still a need for a more active, more stable, and less expensive cathode electrocatalyst to meet the demanding cost and lifetime requirements for many applications, especially for automotive propulsion power.Pt alloys are of great interest as ORR electrocatalysts as they are generally less expensive and have been shown to have enhanced activity versus Pt. [4][5][6] This enhancement in activity was found to be directly correlated with the Pt-Pt interatomic distance 7,8 and to the Pt d-band occupancy in the alloy. [8][9][10] However, there are concerns that the use of base metal alloying elements, which are generally less stable than Pt in acidic environments, could be accompanied by a loss in particle stability and corresponding loss in ORR activity. Conflicting reports exist about the overall stability of Pt alloy catalysts in relation to pure Pt catalysts. 5,6,[11][12][13] Some studies suggest that alloying has a positive effect while others show no significant impact on stability. It is known that relative stability is dependent on particle size, 14-16 the larger the initial particle size the more stable, and the majority of Pt alloy synthesis techniques are based on high temperature annealing processes which result in larger initial particle sizes. Therefore any comparisons between larger annea...

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Section: Resultssupporting

confidence: 88%

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt₃Co Catalyst Degradation in Aqueous and Fuel Cell Environments

Gilbert

Kropf

Kariuki

et al. 2015

J. Electrochem. Soc.

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“…Nonetheless, several research groups have reported the synthesis of ''Pt-skin'' structures upon carbon-supported Pt-alloy nanoparticles. 90,151,168,169 They achieved this either through hightemperature annealing in an inert or reducing atmosphere or by electrochemical cycling in a CO-saturated electrolyte. Each of these studies demonstrated a higher ORR activity than for a standard leached ''Pt-skeleton'' catalyst.…”

Section: Strategies To Improve the Performance Of Pt-alloy Nanoparticlesmentioning

confidence: 99%

Understanding the electrocatalysis of oxygen reduction on platinum and its alloys

Stephens

Bondarenko

Grønbjerg

et al. 2012

Energy Environ. Sci.

1,085

1,024

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The high cost of low temperature fuel cells is to a large part dictated by the high loading of Pt required to catalyse the oxygen reduction reaction (ORR). Arguably the most viable route to decrease the Pt loading, and to hence commercialise these devices, is to improve the ORR activity of Pt by alloying it with other metals. In this perspective paper we provide an overview of the fundamentals underlying the reduction of oxygen on platinum and its alloys. We also report the ORR activity of Pt 5 La for the first time, which shows a 3.5-to 4.5-fold improvement in activity over Pt in the range 0.9 to 0.87 V, respectively. We employ angle resolved X-ray photoelectron spectroscopy and density functional theory calculations to understand the activity of Pt 5 La.

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“…Both the compressive strain effect and the ligand effect contribute to the modification of the surface catalytic properties. 12,32,51,52 Moreover, the Pt-skin surfaces are indeed the stable surface structure in acid solutions for the ORR reactions 9,14,[17][18][19]53 and in the reductive atmospheres for the hydrogenation reactions. [54][55][56] In contrast, there is no consistent picture for the active surface structure of the Pt-based bimetallic catalysts in oxidation reactions, such as the CO oxidation.…”

Section: ' Introductionmentioning

confidence: 99%

Synergetic Effect of Surface and Subsurface Ni Species at Pt−Ni Bimetallic Catalysts for CO Oxidation

et al. 2011

J. Am. Chem. Soc.

269

193

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Various well-defined Ni-Pt(111) model catalysts are constructed at atomiclevel precision under ultra-high-vacuum conditions and characterized by X-ray photoelectron spectroscopy and scanning tunneling microscopy. Subsequent studies of CO oxidation over the surfaces show that a sandwich surface (NiO 1-x /Pt/Ni/Pt(111)) consisting of both surface Ni oxide nanoislands and subsurface Ni atoms at a Pt(111) surface presents the highest reactivity. A similar sandwich structure has been obtained in supported Pt-Ni nanoparticles via activation in H 2 at an intermediate temperature and established by techniques including acid leaching, inductively coupled plasma, and X-ray adsorption nearedge structure. Among the supported Pt-Ni catalysts studied, the sandwich bimetallic catalysts demonstrate the highest activity to CO oxidation, where 100% CO conversion occurs near room temperature. Both surface science studies of model catalysts and catalytic reaction experiments on supported catalysts illustrate the synergetic effect of the surface and subsurface Ni species on the CO oxidation, in which the surface Ni oxide nanoislands activate O 2 , producing atomic O species, while the subsurface Ni atoms further enhance the elementary reaction of CO oxidation with O.

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Origin of Oxygen Reduction Reaction Activity on “Pt₃Co” Nanoparticles: Atomically Resolved Chemical Compositions and Structures

Cited by 286 publications

References 93 publications

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt₃Co Catalyst Degradation in Aqueous and Fuel Cell Environments

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt₃Co Catalyst Degradation in Aqueous and Fuel Cell Environments

Understanding the electrocatalysis of oxygen reduction on platinum and its alloys

Synergetic Effect of Surface and Subsurface Ni Species at Pt−Ni Bimetallic Catalysts for CO Oxidation

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Origin of Oxygen Reduction Reaction Activity on “Pt3Co” Nanoparticles: Atomically Resolved Chemical Compositions and Structures

Cited by 286 publications

References 93 publications

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt3Co Catalyst Degradation in Aqueous and Fuel Cell Environments

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt3Co Catalyst Degradation in Aqueous and Fuel Cell Environments

Understanding the electrocatalysis of oxygen reduction on platinum and its alloys

Synergetic Effect of Surface and Subsurface Ni Species at Pt−Ni Bimetallic Catalysts for CO Oxidation

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Product

Resources

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Origin of Oxygen Reduction Reaction Activity on “Pt₃Co” Nanoparticles: Atomically Resolved Chemical Compositions and Structures

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt₃Co Catalyst Degradation in Aqueous and Fuel Cell Environments

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt₃Co Catalyst Degradation in Aqueous and Fuel Cell Environments