Structure of Co-2 × 2 nanoislands grown on Ag/Ge(111)-√3 × √3 surface studied by scanning tunneling microscopy

Huang, Xiao Lan; Lin, Chun Liang; Tomaszewska, Agnieszka; Chen, Chun Rong; Fu, Tsu Yi

doi:10.1186/1556-276x-7-189

Cited by 6 publications

(4 citation statements)

References 25 publications

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“…For example, Morgenstern et al observed that Co nucleation and growth take place at the steps and on terraces of Ag(111) . Co growth in 3D (Volmer–Weber growth mode) forming islands was also observed on the Ag/Ge(111) surface, Au(111) surface, and HOPG surface …”

Section: Resultsmentioning

confidence: 99%

Electrodeposited Cobalt Nanosheets on Smooth Silver as a Bifunctional Catalyst for OER and ORR: In Situ Structural and Catalytic Characterization

Zan

Amin

Mostafa

et al. 2022

ACS Appl. Mater. Interfaces

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Developing earth-abundant, cost-effective, and active bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is key to boosting sustainable energy systems such as electrolyzers and lithium–air batteries. However, the performance of promising cobalt-based materials is impaired by the external effects of binders and carbon additives as well as inhomogeneous electrode fabrication. In this work, binder- and carbon-free flower-like Co-decorated Ag catalytic nanosheets were in situ-synthesized via a simple electrodeposition approach. The morphology, composition, and structure of Co/Ag before and after OER were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Co/Ag thin film electrodes with various Co contents exhibited a bifunctional activity toward ORR and OER due to a synergistic effect. XPS analysis suggested the formation of Co3O4 as the main active species for OER. In particular, Co (83%)/Ag surface revealed a 60 mV lower ORR overpotential than a pure Ag surface and even lower than drop-casted Co3O4 nanoparticles on Ag surface. Only 1.5% peroxide was generated, suggesting a four-electron transfer ORR. In addition, the OER onset potential on Co/Ag is 60 mV less than Co3O4. Tafel slopes of 71 and 75 mV dec–1 were obtained for ORR and OER, respectively. Importantly, the three-dimensional (3D) growth mechanism of a cobalt layer (∼1 nm) on a well-defined atomic smooth Ag surface is unraveled by in situ electrochemical scanning tunneling microscopy (EC-STM). EC-STM suggests that Co prefers to nucleate at the step edges of Ag and grows in a 3D, forming nanoparticles, where the deposition/dissolution process of the Co adlayer on Ag is reversible. This investigation may provide insights into design strategies of efficient oxygen electrocatalysts.

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Section: Resultsmentioning

confidence: 99%

Electrodeposited Cobalt Nanosheets on Smooth Silver as a Bifunctional Catalyst for OER and ORR: In Situ Structural and Catalytic Characterization

Zan

Amin

Mostafa

et al. 2022

ACS Appl. Mater. Interfaces

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“…Tsay et al demonstrated that Co grown on a Ge(111)/Ag-(√3 × √3)R30°s ubstrate does not intermix with Ge and preserves its magnetic properties [19]. This work was followed by a series of articles that addressed the various aspects of this appealing system [20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Cobalt containing nano-islands on Ge(111)-c(2×8)

Mocking¹,

Poelsema²,

Zandvliet³

2013

Surface Science

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“…This finding was interpreted in terms of buffering properties of the intermediate Ag layer, which prevent the deposited Co atoms from germanide formation. The remarkable properties of the Co/Ag/Ge(111) surface system inspired the work in our laboratory, where, in the last several years, attention was paid to the characterization of the early stages of Co nucleation on the Ag/Ge(111) surface by means of scanning tunneling microscopy (STM) [ 12 - 14 ]. By comparing the method of the Ag/Ge(111) surface fabrication used by Tsay et al with the Ag/Ge(111) surface diagram [ 15 ], we ascribed the buffering properties to the √3 × √3 phase and explained them in the light of the existing structural models of the latter [ 16 , 17 ].…”

Section: Introductionmentioning

confidence: 99%

Nickel-containing nano-sized islands grown on Ge(111)-c(2 × 8) and Ag/Ge(111)-(√3 × √3) surfaces

Tomaszewska

Huang

et al. 2013

Nanoscale Res Lett

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The formation of nano-islands on both a Ge(111)-c(2 × 8) surface and an Ag/Ge(111)-(√3 × √3) surface evaporated with 0.1 ML Ni was investigated by scanning tunneling microscopy (STM). We have noticed that at temperatures lower than 670 K, the reaction between Ni and the individual substrate surfaces proceeds to form different structures: flat-topped islands with a 2√7 × 2√7 or a 3 × 3 reconstruction on the Ni/Ge(111)-c(2 × 8) surface vs. islands with a 7 × 7 reconstruction on the Ni/Ag/Ge(111)-(√3 × √3) surface. From this we have inferred that within a temperature range between room temperature and 670 K, the intermediate Ag layer retards mixing between Ni and Ge atoms. As a result, the grown islands are composed of pure Ni atoms. Within a temperature range from 670 to 770 K, most islands produced on the Ag/Ge(111)-(√3 × √3) surface are identical with those formed on the Ni/Ge(111)-c(2 × 8) surface, suggesting that above 670 K, Ni atoms are likely to bind with Ge atoms. However, an essential difference between STM images of the surfaces under study exists in the appearance of large elongated islands on the Ni/Ag/Ge(111)-(√3 × √3) surface. The formation of the latter is explained in terms of a difference in energy for Ni diffusion on the Ge(111)-c(2 × 8) and Ag/Ge(111)-(√3 × √3) surfaces.

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Structure of Co-2 × 2 nanoislands grown on Ag/Ge(111)-√3 × √3 surface studied by scanning tunneling microscopy

Cited by 6 publications

References 25 publications

Electrodeposited Cobalt Nanosheets on Smooth Silver as a Bifunctional Catalyst for OER and ORR: In Situ Structural and Catalytic Characterization

Electrodeposited Cobalt Nanosheets on Smooth Silver as a Bifunctional Catalyst for OER and ORR: In Situ Structural and Catalytic Characterization

Cobalt containing nano-islands on Ge(111)-c(2×8)

Nickel-containing nano-sized islands grown on Ge(111)-c(2 × 8) and Ag/Ge(111)-(√3 × √3) surfaces

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