In-situ electrochemical atomic force microscopy study of aging of magnetron sputtered Pt-Co nanoalloy thin films during accelerated degradation test

Khalakhan, Ivan; Vorokhta, Mykhailo; Václavů, Michal; Šmíd, Břetislav; Lavková, Jaroslava; Matolı́nová, Iva; Fiala, Roman; Tsud, Nataliya; Škála, Tomáš; Matolín, Vladimı́r

doi:10.1016/j.electacta.2016.06.035

Cited by 24 publications

(14 citation statements)

References 41 publications

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“…Rather drastic changes occur upon cycling to 1.4 V RHE , where AFM reveals pronounced coarsening of the film, resulting in a significant increase of the mean grain size to 11 nm. Moreover, we observe a broadening of the size distribution, which is in correspondence with our previous results ,, and the literature. , …”

Section: Resultssupporting

confidence: 93%

“…Despite aforementioned improvements in activity, binary alloy catalysts often do not maintain their structure during operation. For example, in the acidic environment of fuel cells, transition metals were reported to dissolve, leading to a deterioration of their activity − and, moreover, poisoning of the membrane and the catalyst . To improve the catalyst lifetime, a profound understanding of the degradation mechanisms is needed in order to propose appropriate mitigation strategies.…”

Section: Introductionmentioning

confidence: 99%

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Nanoscale Morphological and Structural Transformations of PtCu Alloy Electrocatalysts during Potentiodynamic Cycling

et al. 2018

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PtCu bimetallic alloys are known to provide better activity than pure platinum in proton exchange membrane fuel cells. However, such catalysts undergo complex degradation processes during fuel cell operation, resulting in deterioration of their activity. By using in situ electrochemical (EC) atomic force microscopy combined with in situ EC infrared reflection absorption spectroscopy, we provide a comprehensive investigation of morphological and structural transformations of PtCu model thin film catalysts during accelerated degradation tests (ADTs). The ADTs consist of potentiodynamic cycling to three different upper potentials relevant for different modes of fuel cell operation. The results show that, depending on the upper potential limit, PtCu alloy electrocatalysts are subject to drastic changes in the surface composition, morphology, and structure.

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Section: Resultssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Nanoscale Morphological and Structural Transformations of PtCu Alloy Electrocatalysts during Potentiodynamic Cycling

et al. 2018

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“…With the availability of the state-of-the-art in situ techniques, fuel cell catalyst degradation has received renewed interest. Advanced in situ electrochemical transmission electron microscopy (TEM), − scanning tunneling microscopy (STM), − atomic force microscopy (AFM), − and X-ray scattering ,,− techniques have been proven to be valuable tools to provide additional insights into the catalyst degradation mechanisms by investigating its behavior directly under specific electrochemical reactions. For example, Jacobse et al .…”

Section: Introductionmentioning

confidence: 99%

Evolution of the PtNi Bimetallic Alloy Fuel Cell Catalyst under Simulated Operational Conditions

Khalakhan

Bogar

Vorokhta

et al. 2020

ACS Appl. Mater. Interfaces

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Comprehensive understanding of the catalyst corrosion dynamics is a prerequisite for the development of an efficient cathode catalyst in proton-exchange membrane fuel cells. To reach this aim, the behavior of fuel cell catalysts must be investigated directly under reaction conditions. Herein, we applied a strategic combination of in situ/online techniques: in situ electrochemical atomic force microscopy, in situ grazing incidence small angle X-ray scattering, and electrochemical scanning flow cell with online detection by inductively coupled plasma mass spectrometry. This combination of techniques allows indepth investigation of the potential-dependent surface restructuring of a PtNi model thin film catalyst during potentiodynamic cycling in an aqueous acidic electrolyte. The study reveals a clear correlation between the upper potential limit and structural behavior of the PtNi catalyst, namely, its dealloying and coarsening. The results show that at 0.6 and 1.0 V RHE upper potentials, the PtNi catalyst essentially preserves its structure during the entire cycling procedure. The crucial changes in the morphology of PtNi layers are found to occur at 1.3 and 1.5 V RHE cycling potentials. Strong dealloying at the early stage of cycling is substituted with strong coarsening of catalyst particles at the later stage. The coarsening at the later stage of cycling is assigned to the electrochemical Ostwald ripening process.

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“…While technology has now started reaching cost-efficient targets by replacing conventional platinum catalysts with platinum alloys with cheaper transition metals, − the problem remains with durability because of their higher susceptibility to corrosion and deactivation. Complex bimetallic systems have been found to lose their superficial structure and chemical integrity due to the harsh conditions in the PEMFC cathode, such as the relatively high potentials and low pH. − To date, several different processes have been identified causing reduction of performance of fuel cells assembled with benchmark Pt/C nanoparticle catalysts. − Corrosion of the carbon support and platinum dissolution were found to act as primary sources of degradation, triggering a set of secondary degradation mechanisms like particle detachment, particle agglomeration (coalescence), and Ostwald ripening. , The latter two are responsible for a gradual increase of catalyst nanoparticle size, resulting in a reduction of the active surface area and consequently a decrease in fuel cell efficiency. In turn, in the case of a binary PtM system (with M being a transition metal), faster dissolution of the less noble metal due to high overpotentials introduces a second degree of freedom, further affecting catalyst degradation pathways.…”

Section: Introductionmentioning

confidence: 99%

Interplay Among Dealloying, Ostwald Ripening, and Coalescence in Pt_XNi_100–X Bimetallic Alloys under Fuel-Cell-Related Conditions

et al. 2021

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Platinum-based bimetallic alloys have been largely investigated during the last few years as a valid alternative to bare Pt cathode catalysts for proton-exchange membrane fuel cells (PEMFCs) to improve their cost-efficiency. Nonetheless, Pt bimetallic alloys are characterized by a reduced stability, which is poorly understood at a fundamental level. It is thus essential to describe the entire chain of interconnected degradation mechanisms to formulate a comprehensive model of catalyst degradation that will help interpret bimetallic alloy behavior in real complex fuel cell systems. By combining in situ inductively coupled plasma mass spectroscopy, in situ grazing-incidence small-angle X-ray scattering, and ex situ scanning electron microscopy, we have studied the morphological evolution of Pt X Ni100–X model catalysts with different Ni contents (ranging from 0 to 75%) undergoing potentiodynamic cycling to two different upper potentials mimicking the different operational conditions of a PEMFC: 1.0 and 1.3 VRHE. Data analysis allowed us to develop a methodology to distinguish the influence of Ni dissolution, particle coalescence, and Ostwald ripening on particle size distribution and interparticle distance and to realize time-dependent interplay maps to highlight the timeframe in which the aforementioned phenomena are prevailing or coexisting. Results show that Ni dissolution is the only phenomenon inducing morphological evolution when the lower upper potential is chosen. On the contrary, at 1.3 VRHE, Ni dissolution is rapidly overcome by particle coalescence at first and by Ostwald ripening in the later stages of the investigated time range. The onset of every phenomenon was found to occur earlier in time for larger values of Ni concentrations.

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In-situ electrochemical atomic force microscopy study of aging of magnetron sputtered Pt-Co nanoalloy thin films during accelerated degradation test

Cited by 24 publications

References 41 publications

Nanoscale Morphological and Structural Transformations of PtCu Alloy Electrocatalysts during Potentiodynamic Cycling

Nanoscale Morphological and Structural Transformations of PtCu Alloy Electrocatalysts during Potentiodynamic Cycling

Evolution of the PtNi Bimetallic Alloy Fuel Cell Catalyst under Simulated Operational Conditions

Interplay Among Dealloying, Ostwald Ripening, and Coalescence in Pt_XNi_100–X Bimetallic Alloys under Fuel-Cell-Related Conditions

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In-situ electrochemical atomic force microscopy study of aging of magnetron sputtered Pt-Co nanoalloy thin films during accelerated degradation test

Cited by 24 publications

References 41 publications

Nanoscale Morphological and Structural Transformations of PtCu Alloy Electrocatalysts during Potentiodynamic Cycling

Nanoscale Morphological and Structural Transformations of PtCu Alloy Electrocatalysts during Potentiodynamic Cycling

Evolution of the PtNi Bimetallic Alloy Fuel Cell Catalyst under Simulated Operational Conditions

Interplay Among Dealloying, Ostwald Ripening, and Coalescence in PtXNi100–X Bimetallic Alloys under Fuel-Cell-Related Conditions

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Interplay Among Dealloying, Ostwald Ripening, and Coalescence in Pt_XNi_100–X Bimetallic Alloys under Fuel-Cell-Related Conditions