Disproportional surface segregation in ligand-free gold–silver alloy solid solution nanoparticles, and its implication for catalysis and biomedicine

Stein, Frederic; Kohsakowski, Sebastian; Martínez‐Hincapié, Ricardo; Reichenberger, Sven; Rehbock, Christoph; Colic, Victor; Guay, Daniel; Barcikowski, Stephan

doi:10.1039/d2fd00092j

Cited by 6 publications

(15 citation statements)

References 79 publications

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“…For the case of CuAg and AuAg, both metals exhibit an fcc structure and, although their Ag enrichment could also be explained in terms of lower surface energies, it has been speculated that the formation of a surface enriched with the less abundant element is driven by entropy. 54 The different metals' oxophilicity also plays a role in the final surface Ag content. Since the less noble metals will tend to oxidize in the presence of O 2 , there could be a driving force at positive potentials to form a surface oxide, which requires the emergence of the underlying metal to the surface and thus a decrease in Ag ECSA.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…For CoAg and FeAg, both host metals exhibit a different crystal structure than Ag (hcp and bcc vs fcc), which results in a system where the formation of an alloy is more thermodynamically hindered and thus a more heterogeneous surface is formed. For the case of CuAg and AuAg, both metals exhibit an fcc structure and, although their Ag enrichment could also be explained in terms of lower surface energies, it has been speculated that the formation of a surface enriched with the less abundant element is driven by entropy . The different metals’ oxophilicity also plays a role in the final surface Ag content.…”

Section: Resultsmentioning

confidence: 99%

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Tuning the Activity of Silver Alloys for the Oxygen Reduction Reaction in Alkaline Media

Montserrat‐Sisó

Wickman

2023

ACS Appl. Energy Mater.

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Ag-based catalysts have recently attracted much attention as potential candidates to substitute costly Pt-based electrocatalysts for the oxygen reduction reaction (ORR) in alkaline media. Although the electrocatalytic activity of Pt-based alloys is known to exhibit a strong dependence on their electronic structures, a relationship between electronic structure and the ORR mechanism in Ag-based alloys still remains to be elucidated. Herein, by means of physical vapor deposition, we prepare Ag binary thin films (CoAg, CuAg, AuAg, and FeAg) with well-controlled compositions as a tool to investigate the ORR mechanism on Ag surfaces. The bimetallic thin films are evaluated for their ORR performance in alkaline media, and their specific activity at 0.8 VRHE is shown to correlate with the Ag electronic structure. Even though all thin films show different responses to potential cycling, all bimetallic samples exhibit a surface Ag enrichment after ORR. It is shown that the ORR occurs through different mechanisms on these Ag-rich surfaces, which in turn is potential-dependent. Tafel slopes reveal faster ORR kinetics at low overpotentials on all surfaces, whereas only CuAg surpasses pure Ag at higher overpotentials. Moreover, despite their incomplete O2 reduction, CuAg and AuAg exhibit an overall superior ORR activity over pure Ag, with a more than 2-fold increase in specific activity at 0.8 VRHE attributed to enhancements originating from electronic effects and surface defects, respectively. Since the potential-dependent improved ORR mechanism observed for Ag bimetallic samples makes a rational design of Ag-based electrocatalysts difficult, these results aim to provide insights for a more tailored design of electrocatalysts by shedding light on the mechanisms through which the ORR kinetics are improved on Ag surfaces in alkaline media.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Tuning the Activity of Silver Alloys for the Oxygen Reduction Reaction in Alkaline Media

Montserrat‐Sisó

Wickman

2023

ACS Appl. Energy Mater.

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“…[54][55][56][57][58][59][60][61][62][63][64] Second, while metallic species can be found in different chemical arrangements with the possibility of surface segregation, there is currently no consensus in the literature on whether gold or silver is more likely to segregate on the surface. 23,57,[65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80] In this contribution, we experimentally show that gas-phase synthesis can lead to decahedral and icosahedral AuAg nanoalloys both exhibiting unambiguous gold surface segregation. Our machine-learning assisted simulations confirmed these experimental findings and enabled investigations over a wider spectrum of chemical compositions.…”

Section: Introductionmentioning

confidence: 84%

“…54–64 Second, while metallic species can be found in different chemical arrangements with the possibility of surface segregation, there is currently no consensus in the literature on whether gold or silver is more likely to segregate on the surface. 23,57,65–80…”

Section: Introductionmentioning

confidence: 99%

Exploring the formation of gold/silver nanoalloys with gas-phase synthesis and machine-learning assisted simulations

Gromoff,

Benzo,

Saidi

et al. 2024

Nanoscale

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“…Metal nanoparticles (NPs) have unique properties, which makes them useful for many applications, such as catalysis [1,2] , biotechnology [3,4] , and modifying feedstock materials within e.g., powder bed fusion using a laser beam (PBF-LB) [5,6] , which enables small series production of fully dense metallic parts with high geometrical freedom, good dimensional accuracy, and reasonable surface finish [7] . Here, however, currently, available metal powder feedstocks have been developed over the last decades for conventional Powder Metallurgy production routes, such as hot compaction, pressing, and sintering or Metal Injection Molding.…”

Section: Introductionmentioning

confidence: 99%

Upscaled laser synthesis of copper nanoparticles in acetone to correlate the surface modification of Nd-Fe-B feedstock properties with part properties after full melting and rapid solidification

Gabriel

Liu

Staab

et al. 2023

Preprint

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The possibilities of nanoadditivation to achieve finer, more equiaxed grains unlock huge potential for the application field of functional materials, e.g. Nd-Fe-B magnets, where the control of the microstructure and the composition is of significant importance. The surface modification of hard magnetic microparticles by non-magnetic nanoparticles (NPs) opens a novel field of research. Here, especially Cu NPs with low amounts of oxides are of high relevance as colloidal nano-additive material. To increase the productivity of surfactant-free, laser-generated Cu NPs, we performed a process parameter study via laser ablation in acetone aiming for the highest possible productivity, increasing the throughput of NP additivation on the surface of functional feedstock micro powders. By optimizing the process parameters of laser power, laser fluence, repetition rate, volume flow, and spot size, a productivity of 0.19 µg/J of Cu NPs in acetone was achieved. Then we investigated how a fine microstructure of the magnet powder MQP-S can be retained to some extent along the process chain, throughout the melting and resolidification process during suction casting. A loading series of Cu NP nanoadditivation on magnet micro powders of 0.1, 0.5, 1.0, and 2.5 wt.% was analyzed regarding magnetic properties and microstructure of the as-built part. Using full melting conditions of MQP-S by producing samples via suction casting modified with different amounts of Cu NP additions leads to finer grains, but increasing α-Fe content. Overall, the results enable higher production rates of Cu NPs in acetone and provide insights into the influence of NP-supporting characteristics on the properties of permanent magnet micro powders after full melting and resolidification.

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Disproportional surface segregation in ligand-free gold–silver alloy solid solution nanoparticles, and its implication for catalysis and biomedicine

Abstract: Catalytic activity and toxicity of mixed-metal nanoparticles have been shown to correlate often and are known to be ruled by surface composition. The surface chemistry of fully inorganic, ligand-free silver-gold...

Cited by 6 publications

References 79 publications

Tuning the Activity of Silver Alloys for the Oxygen Reduction Reaction in Alkaline Media

Tuning the Activity of Silver Alloys for the Oxygen Reduction Reaction in Alkaline Media

Exploring the formation of gold/silver nanoalloys with gas-phase synthesis and machine-learning assisted simulations

Upscaled laser synthesis of copper nanoparticles in acetone to correlate the surface modification of Nd-Fe-B feedstock properties with part properties after full melting and rapid solidification

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