In Situ Small-Angle X-ray Scattering Observation of Pt Catalyst Particle Growth During Potential Cycling

Smith, Matt C.; Gilbert, James A.; Mawdsley, Jennifer R.; Seifert, Sönke; Myers, Deborah J.

doi:10.1021/ja801138t

Cited by 80 publications

(90 citation statements)

References 14 publications

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“…The reduction in the electrochemical surface area is mostly caused by the Ostwald ripening phenomenon where Pt dissolution and redeposition occur during potential cycling in the investigated potential range resulting in an irreversible change in the Pt particle size. 39 By contrast, no significant change occurred in the CV of OMCN that does not inherently undergo a similar dissolution/redeposition process to Pt, indicating the superior structural durability of OMCN with respect to the Pt/C catalyst in an acidic medium. Figure 8a,b compares the ORR activities of OMCN and Pt/C after the ADT and methanol additions at 900 rpm in the oxygensaturated electrolyte.…”

Section: Articlementioning

confidence: 96%

Ordered Mesoporous Carbon Nitrides with Graphitic Frameworks as Metal-Free, Highly Durable, Methanol-Tolerant Oxygen Reduction Catalysts in an Acidic Medium

et al. 2011

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Developments of high-performance cost-effective electrocatalyts that can replace Pt catalysts have been a central theme in polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs). In this direction, nitrogen-doped carbon nanostructures free of metallic components have attracted particular attention. Here we show that directing graphitic carbon nitride frameworks into mesoporous architecture can generate a highly promising metal-free electrocatalyst for an oxygen reduction reaction (ORR) in an acidic medium. The ordered mesoporous carbon nitride (OMCN) was synthesized with a nanocasting strategy using ordered mesoporous silica as a template. A variety of characterizations revealed that the OMCN is constructed with graphitic carbon nitride frameworks and ordered arrays of uniform mesopores. The OMCN showed significantly enhanced electrocatalytic activity for ORR compared to bulk carbon nitride and ordered mesoporous carbon in terms of the current density and onset potential. A high surface area and an increased density of catalytically active nitrogen groups in the OMCN appear to contribute concomitantly to the enhanced performance of the OMCN. Furthermore, the OMCN exhibited superior durability and methanol tolerance to a Pt/C catalyst, suggesting its widespread utilization as an electrocatalyst for PEMFCs and DMFCs.

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Section: Articlementioning

confidence: 96%

Ordered Mesoporous Carbon Nitrides with Graphitic Frameworks as Metal-Free, Highly Durable, Methanol-Tolerant Oxygen Reduction Catalysts in an Acidic Medium

et al. 2011

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“…For practical use, reducing the use of Pt, a precious metal, while maintaining the electrocatalytic activity or increasing the mass activity (MA) of Pt is highly desired and urgently needed. To this end, nanoparticles of various Pt-based alloys and bimetals have been prepared [1][2][3][4][5][6][7][8]. However, recently, it seems that the strategy has approached its limit.…”

Section: Introductionmentioning

confidence: 99%

Electrocatalytic activity for oxygen reduction reaction of Pt nanoparticle catalysts with narrow size distribution prepared from (n=3–8) complexes

Higuchi¹,

Taguchi²,

Hayashi³

et al. 2011

Journal of Electroanalytical Chemistry

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“…14,[18][19][20][21][22] A comprehensive discussion of the ASAXS method and its use in characterizing carbon-supported metal catalysts can be found in several publications and textbooks. [23][24][25][26][27][28][29] One advantage this technique has is its ability to obtain element specific PSDs.…”

mentioning

confidence: 99%

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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In Situ Small-Angle X-ray Scattering Observation of Pt Catalyst Particle Growth During Potential Cycling

Cited by 80 publications

References 14 publications

Ordered Mesoporous Carbon Nitrides with Graphitic Frameworks as Metal-Free, Highly Durable, Methanol-Tolerant Oxygen Reduction Catalysts in an Acidic Medium

Ordered Mesoporous Carbon Nitrides with Graphitic Frameworks as Metal-Free, Highly Durable, Methanol-Tolerant Oxygen Reduction Catalysts in an Acidic Medium

Electrocatalytic activity for oxygen reduction reaction of Pt nanoparticle catalysts with narrow size distribution prepared from (n=3–8) complexes

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

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In Situ Small-Angle X-ray Scattering Observation of Pt Catalyst Particle Growth During Potential Cycling

Cited by 80 publications

References 14 publications

Ordered Mesoporous Carbon Nitrides with Graphitic Frameworks as Metal-Free, Highly Durable, Methanol-Tolerant Oxygen Reduction Catalysts in an Acidic Medium

Ordered Mesoporous Carbon Nitrides with Graphitic Frameworks as Metal-Free, Highly Durable, Methanol-Tolerant Oxygen Reduction Catalysts in an Acidic Medium

Electrocatalytic activity for oxygen reduction reaction of Pt nanoparticle catalysts with narrow size distribution prepared from (n=3–8) complexes

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

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