Synthesis of a calcium-bridged siloxene by a solid state reaction for optical and electrochemical properties

Imagawa, Haruo; Takahashi, Naoko; Nonaka, Takamasa; Kato, Yuichi; Nishikawa, Kaneyasu; Itahara, Hiroshi

doi:10.1039/c5ta00321k

Cited by 35 publications

(50 citation statements)

References 23 publications

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“…In addition, Ca‐rich regions would be partially Ca‐extracted CaSi 2 particles (Figures c and ). These particles would not be detected by XRD measurement because Ca extraction induced structural disorder . The average Ca:Si ratio was 0.29:2 and the amount of Cl was less than 0.1 at% for the entire region of the SEM image in Figure (A).…”

Section: Resultsmentioning

confidence: 98%

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Formation mechanism of Cu₂O particles using layered CaSi₂ as a reduction/oxidation mediator

Itahara¹,

Nakano²

2019

J Am Ceram Soc

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We demonstrate that Cu2O particles can be produced along with siloxene formation by simply dispersing layered CaSi2 into an aqueous solution of CuCl2 and HCl at room temperature. The Cl− ions induce oxidative extraction of Ca from CaSi2 to form siloxene and trigger the reductive deposition of Cu particles. All particles are then gradually oxidized to form Cu2O particles under optimized conditions as follows. A trace amount of residual CaSi2 is dissolved in the solution, which provides OH− ions, and a portion of the formed Cu particles are dissolved as [Cu(OH)4]2− ions. Accordingly, Cu2O particles would be formed through the comproportionation reaction between Cu and [Cu(OH)4]2− ions in the solution. However, under conditions with an excess amount of Cl− ions results in further oxidation of Cu to also form Cu2Cl(OH)3. Thus, CaSi2 acts as an effective reduction and/or oxidation mediator to tune the number of Cl− and OH− ions and control the oxidation state of Cu.

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Section: Resultsmentioning

confidence: 98%

“…The dangling bonds or the surface of the formed siloxene are reactive. Siloxene may also have introduced an advantage as a mixing counter partner with Cu 2 O because siloxene is a semiconductor with photocatalytic activity and anode performance for Li ion batteries …”

Section: Introductionmentioning

confidence: 99%

Formation mechanism of Cu₂O particles using layered CaSi₂ as a reduction/oxidation mediator

Itahara¹,

Nakano²

2019

J Am Ceram Soc

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“…The higher deposition rate of Ca than the conventional RDE, control of the annealing temperature to induce the Kirkendall effect, and the choice of the growth surface play important roles to obtain the ordered microwalls. CaSi 2 powders are known as raw materials for the fabrication of functional Si‐based nanomaterials with characteristic electrochemical and optical properties . Si‐based nanosheets attached firmly on the current collector are desired as electrode materials for secondary batteries because a reduction of the electrical contact resistance is expected.…”

Section: Discussionmentioning

confidence: 99%

“…The layered CaSi 2 is transformed, based on the Ca extraction reactions, into organic‐modified Si nanosheets and Si‐based nanoflake particles . In a previous report, it was shown that nanoflakes aggregated with slit‐like nanopores were prepared by using layered CaSi 2 powders (particle size <32 μm) as a raw material and that they exhibited nanostructure‐derived characteristic properties such as an excellent anode performance in Li‐ion batteries and a broad absorption tail ranging from visible to ultraviolet wavelengths . For battery applications, electrode materials attached firmly on the current collector are desired to reduce the electrical contact resistance.…”

Section: Introductionmentioning

confidence: 99%

Ordered CaSi₂ Microwall Arrays on Si Substrates Induced by the Kirkendall Effect

Meng

Ueki

Tatsuoka

et al. 2017

Chemistry A European J

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We have specified the synthetic conditions to obtain one-directionally ordered CaSi microwall arrays vertically grown on a Si substrate. Our basic concept is based on the utilization of the Kirkendall effect for reactive deposition epitaxy (RDE). We found for the first time that: 1) a much larger Ca vapor supply on the Si substrate than the conventional RDE, 2) the adoption of a two-step heating process, and 3) the selection of the crystal axis of the Si surface are the keys to control the microstructures of CaSi on the Si substrate. The CaSi phase was first formed on Si, then the CaSi phase was formed at the CaSi/Si interface. Based on the Kirkendall effect, the interdiffusion of Ca and Si was enhanced in the vertical direction rather than in the parallel direction to the Si surface. CaSi tends to grow along four equivalent Si{111} planes, however, the specific orientation of the Si surface resulted in CaSi microwalls grown along its Si(111‾ ) plane, the only plane directing nearly vertical to the surface among the Si{111} planes. These results suggest that the Kirkendall effect under asymmetric growth of target materials would be a rational strategy to obtain their ordered microstructures.

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“…The common method to prepare siloxene is the deintercalation of Ca atom by different oxidant (metal chlorides, I 2 , aqueous HCl, etc. )34,35 from CaSi 2 , which is a hexagonal layered structure consisting of alternating Ca layers and corrugated Si (111) planes 36. In the fields of solar‐electric energy conversion37 and lithium storage,38,39 siloxene has been demonstrated as an efficient metal‐free semiconductor for photocatalytic water‐splitting, and an excellent anode material for Li‐ion batteries.…”

Section: Introductionmentioning

confidence: 99%

Highly Stable Lithium−Sulfur Batteries Promised by Siloxene: An Effective Cathode Material to Regulate the Adsorption and Conversion of Polysulfides

Wang

Zhou

Huang

et al. 2020

Adv Funct Materials

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Designing an appropriate cathode is still a challenge for lithium–sulfur batteries (LSBs) to overcome the polysulfides shuttling and sluggish redox reactions. Herein, 2D siloxene nanosheets are developed by a rational wet‐chemistry exfoliation approach, from which S@siloxene@graphene (Si/G) hybrids are constructed as cathodes in Li‐S cells. The siloxene possesses corrugated 2D Si backbone with abundant O grafted in Si6 rings and hydroxyl‐functionalized surface, which can effectively intercept polysulfides via synergistic effects of chemical trapping capability and kinetically enhanced polysulfides conversion. Theoretical analysis further reveals that siloxene can significantly elevate the adsorption energies and lower energy barrier for Li+ diffusion. The LSBs assembled with 2D Si/G hybrid cathodes exhibit greatly enhanced rate performance (919, 759, and 646 mAh g−1 at 4 C with sulfur loading of 1, 2.9, and 4.2 mg cm−2, respectively) and superb durability (demonstrated by 1000 cycles with an initial capacity of 951 mAh g−1 and negligible 0.032% decay rate at 1 C with sulfur loading of 4.2 mg cm−2). It is expected that the study presented here may open up a new vision toward developing high‐performance LSBs with siloxene for practical applications.

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Synthesis of a calcium-bridged siloxene by a solid state reaction for optical and electrochemical properties

Abstract: A Ca-bridged siloxene resulting from the deintercalation of Ca from CaSi2was synthesized, which shows stable Li storage performance.

Cited by 35 publications

References 23 publications

Formation mechanism of Cu₂O particles using layered CaSi₂ as a reduction/oxidation mediator

Formation mechanism of Cu₂O particles using layered CaSi₂ as a reduction/oxidation mediator

Ordered CaSi₂ Microwall Arrays on Si Substrates Induced by the Kirkendall Effect

Highly Stable Lithium−Sulfur Batteries Promised by Siloxene: An Effective Cathode Material to Regulate the Adsorption and Conversion of Polysulfides

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Synthesis of a calcium-bridged siloxene by a solid state reaction for optical and electrochemical properties

Abstract: A Ca-bridged siloxene resulting from the deintercalation of Ca from CaSi2was synthesized, which shows stable Li storage performance.

Cited by 35 publications

References 23 publications

Formation mechanism of Cu2O particles using layered CaSi2 as a reduction/oxidation mediator

Formation mechanism of Cu2O particles using layered CaSi2 as a reduction/oxidation mediator

Ordered CaSi2 Microwall Arrays on Si Substrates Induced by the Kirkendall Effect

Highly Stable Lithium−Sulfur Batteries Promised by Siloxene: An Effective Cathode Material to Regulate the Adsorption and Conversion of Polysulfides

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Formation mechanism of Cu₂O particles using layered CaSi₂ as a reduction/oxidation mediator

Formation mechanism of Cu₂O particles using layered CaSi₂ as a reduction/oxidation mediator

Ordered CaSi₂ Microwall Arrays on Si Substrates Induced by the Kirkendall Effect