The growth and degradation of binary and ternary octahedral Pt–Ni-based fuel cell catalyst nanoparticles studied using advanced transmission electron microscopy

Heggen, Marc; Gocyla, Martin; Dunin-Borkowski, Rafal E.

doi:10.1080/23746149.2017.1282834

Cited by 10 publications

(11 citation statements)

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“…The degradation of Pt-based alloy nanoparticles will depend on the content and local distribution of the elements present; a third element may effectively improve the stability of such binary Pt-based catalyst. , In our previous study, introducing a third element not only reduced pore formation after EA but additionally, as shown experimentally and explained by kinetic Monte Carlo (KMC) simulations, changed the evolution of nanoparticle shape due to modified properties of Pt-skin . These preliminary studies demonstrated a high complexity and interdependence of the processes occurring during EA.…”

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confidence: 83%

Atomically Resolved Anisotropic Electrochemical Shaping of Nano-electrocatalyst

et al. 2019

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Catalytic properties of advanced functional materials are determined by their surface and near-surface atomic structure, composition, morphology, defects, compressive and tensile stresses, etc; also known as a structure–activity relationship. The catalysts structural properties are dynamically changing as they perform via complex phenomenon dependent on the reaction conditions. In turn, not just the structural features but even more importantly, catalytic characteristics of nanoparticles get altered. Definitive conclusions about these phenomena are not possible with imaging of random nanoparticles with unknown atomic structure history. Using a contemporary PtCu-alloy electrocatalyst as a model system, a unique approach allowing unprecedented insight into the morphological dynamics on the atomic-scale caused by the process of dealloying is presented. Observing the detailed structure and morphology of the same nanoparticle at different stages of electrochemical treatment reveals new insights into atomic-scale processes such as size, faceting, strain and porosity development. Furthermore, based on precise atomically resolved microscopy data, Kinetic Monte Carlo (KMC) simulations provide further feedback into the physical parameters governing electrochemically induced structural dynamics. This work introduces a unique approach toward observation and understanding of nanoparticles dynamic changes on the atomic level and paves the way for an understanding of the structure–stability relationship.

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confidence: 83%

Atomically Resolved Anisotropic Electrochemical Shaping of Nano-electrocatalyst

et al. 2019

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“…Ternary octahedral Pt–Ni-based nanoparticles, such as Pt–Ni–Fe and Pt–Ni–Cu NPs, characterized by high activity and promising stability for the ORR, were recently described . Owing to the excellent catalytical properties of both Pt–Ni and Pt–Co bimetallic systems, ternary Pt–Ni–Co NPs have also attracted much attention, with precise control over the composition, size, and phase of the nanoparticles during synthesis and subsequent treatment identified as being crucial for their electrocatalytic activity and stability. , Most of the combinations, however, still experience transition-metal leakage, and addition of noble metals with higher dissolution potentials has proved to be a useful strategy . A recent synthesis of PtCo NPs with added Au showed improved durability by weakening the binding energy of surface oxygen species and suppressed Co surface segregation .…”

Section: Introductionmentioning

confidence: 99%

Adsorbate-Induced Segregation of Cobalt from PtCo Nanoparticles: Modeling Au Doping and Core AuCo Alloying for the Improvement of Fuel Cell Cathode Catalysts

Farkaš

Perry²,

Jones

et al. 2020

J. Phys. Chem. C

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Platinum, when used as a cathode material for the oxygen reduction reaction, suffers from high overpotential and possible dissolution, in addition to the scarcity of the metal and resulting cost. Although the introduction of cobalt has been reported to improve reaction kinetics and decrease the precious metal loading, surface segregation or complete leakage of Co atoms causes degradation of the membrane electrode assembly, and either of these scenarios of structural rearrangement eventually decreases catalytic power. Ternary PtCo alloys with noble metals could possibly maintain activity with a higher dissolution potential. First-principles-based theoretical methods are utilized to identify the critical factors affecting segregation in Pt–Co binary and Pt–Co–Au ternary nanoparticles in the presence of oxidizing species. With a decreasing share of Pt, surface segregation of Co atoms was already found to become thermodynamically viable in the PtCo systems at low oxygen concentrations, which is assigned to high charge transfer between species. While the introduction of gold as a dopant caused structural changes that favor segregation of Co, creation of CoAu alloy core is calculated to significantly suppress Co leakage through modification of the electronic properties. The theoretical framework of geometrically different ternary systems provides a new route for the rational design of oxygen reduction catalysts.

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“…Several research groups have shown impressive results about the activity of Pt‐Ni octahedral nanocatalysts, synthesized via colloidal methods, toward the oxygen reduction reaction (ORR). [ 1–5 ] The results are usually obtained from rotating disc electrode (RDE) electrocatalytic measurements on small synthetic batches and compared to standard catalysts from catalyst manufacturers (Johnson Matthey in the case of our study). This methodology is considered a prerequisite before scaling‐up the synthesis and testing the catalyst in a genuine proton exchange membrane fuel cell (PEMFC).…”

Section: Introductionmentioning

confidence: 99%

Octahedral to Cuboctahedral Shape Transition in 6 nm Pt₃Ni Nanocrystals for Oxygen Reduction Reaction Electrocatalysis

Zysler

Zitoun

2020

Part & Part Syst Charact

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this study), leads to difficulty producing scaled-up catalyst quantities sufficient for a PEMFC test.Extensive efforts have been carried out to obtain control on the shape, exposed facets, [7] and size of Pt-Ni bimetallic nanoparticles (NPs); [8][9][10][11] with different elemental composition, [12] surface composition, [13][14][15] and porosity [16] to enhance the ORR activity and durability with the lowest possible amount of Pt. Therefore, it is extremely important to design the synthesis of shape-controlled Pt-Ni NPs toward their potential use in cathode layers of PEMFCs. The syntheses of Pt-Ni NPs have explored a variety of metal precursors, [17] postsynthesis treatment, [18] and dealloying or etching processes [19][20][21][22][23][24] to yield the best electrocatalysts. The ability to tune the morphology by surfactantassisted synthesis [25] has been instrumental in enhancing the mass activity of polyhedral Pt-Ni NPs. The reaction mechanism of growth [26] and etching [27] has been scarcely reported.Solvothermal synthesis usually generates octahedral NPs with high ORR activity of the {111} facets and yield bimetallic nanoparticles with a Pt skeleton and a Ni-rich core. [28] Pt-Ni cuboctahedra nanocrystals with a high activity toward the same reaction have been reported. Cui et al. [13] have reported very high activities. Recently, a very high specific activity has been reported for a well-defined octahedral particle but the rather large particle size (10-15 nm) impedes the mass activity. [29] In this paper, we investigate the structure-properties relationship of Pt 3 Ni NPs with a particle size of 5-6 nm, which is close to the optimal value for ORR electrocatalysts and the lowest reported to still display shape and preferential crystallographic orientation of the facets. We show how a simple synthetic parameter, the ratio between the solution and the free volume in the reactor, leads to the formation of octahedral or cuboctahedral PtNi nanocrystals. Interestingly, each shape displays a different chemical ordering with Pt or Nirich surface, as evidenced by high-angle annular dark-field (HAADF)-high-resolution transmission electron microscopy (HRTEM) mapping. In the case of cuboctahedral NPs, after a few cyclic voltammograms in acidic medium, the NPs retain their geometry but display a Pt-rich skin which explains their ORR activity.Pt 3 Ni stands as one of the most active electrocatalysts for the oxygen reduction reaction (ORR). The activity varies with the morphology of the nanocrystals with a high activity observed for the octahedral shape where only the high density {111} crystallographic planes are exposed. Herein, the synthesis of 6 nm Pt 3 Ni octahedral nanocrystals with a Pt enriched shell or cuboctahedral nanocrystals with a Ni enriched shell is described. Interestingly, the cuboctahedral nanocrystals display a six-pointed star/skeleton of platinum, which features a very uncommon atomic distribution. In the synthesis, a decrease in the oxygen partial pressure induces the transition from octahedral to cub...

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The growth and degradation of binary and ternary octahedral Pt–Ni-based fuel cell catalyst nanoparticles studied using advanced transmission electron microscopy

Cited by 10 publications

References 95 publications

Atomically Resolved Anisotropic Electrochemical Shaping of Nano-electrocatalyst

Atomically Resolved Anisotropic Electrochemical Shaping of Nano-electrocatalyst

Adsorbate-Induced Segregation of Cobalt from PtCo Nanoparticles: Modeling Au Doping and Core AuCo Alloying for the Improvement of Fuel Cell Cathode Catalysts

Octahedral to Cuboctahedral Shape Transition in 6 nm Pt₃Ni Nanocrystals for Oxygen Reduction Reaction Electrocatalysis

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The growth and degradation of binary and ternary octahedral Pt–Ni-based fuel cell catalyst nanoparticles studied using advanced transmission electron microscopy

Cited by 10 publications

References 95 publications

Atomically Resolved Anisotropic Electrochemical Shaping of Nano-electrocatalyst

Atomically Resolved Anisotropic Electrochemical Shaping of Nano-electrocatalyst

Adsorbate-Induced Segregation of Cobalt from PtCo Nanoparticles: Modeling Au Doping and Core AuCo Alloying for the Improvement of Fuel Cell Cathode Catalysts

Octahedral to Cuboctahedral Shape Transition in 6 nm Pt3Ni Nanocrystals for Oxygen Reduction Reaction Electrocatalysis

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Octahedral to Cuboctahedral Shape Transition in 6 nm Pt₃Ni Nanocrystals for Oxygen Reduction Reaction Electrocatalysis