Revealing salt-expedited reduction mechanism for hollow silicon microsphere formation in bi-functional halide melts

The thermochemical reduction of silica to silicon using chemical reductants requires high temperature and has a high activation energy, which depends on the melting temperature of the reductant. The addition of bi-functional molten salts with a low melting temperature may reduce the required energy,...

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Bibliographic Details
Published in:Communications chemistry 2018-08, Vol.1 (1), Article 42
Main Authors: Song, Gyujin, Ryu, Jaegeon, Kim, Jin Chul, Lee, Jeong Hyeon, Kim, Sungho, Wang, Chongmin, Kwak, Sang Kyu, Park, Soojin
Format: Article
Language:English
Subjects:
639/301/299/161/891
639/4077/4079/891
Aluminum
Aluminum chloride
Chemistry
Chemistry and Materials Science
Chemistry/Food Science
Chlorides
Heat of reaction
High temperature
Low temperature
Melt temperature
Molten salts
Porous silicon
Reaction mechanisms
Silicon dioxide
Thermochemical reduction
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Summary:The thermochemical reduction of silica to silicon using chemical reductants requires high temperature and has a high activation energy, which depends on the melting temperature of the reductant. The addition of bi-functional molten salts with a low melting temperature may reduce the required energy, and several examples using molten salts have been demonstrated. Here we study the mechanism of reduction of silica in the presence of aluminum metal reductant and aluminum chloride as bi-functional molten salts. An aluminum–aluminum chloride complex plays a key role in the reduction mechanism, reacting with the oxygen of the silica surfaces to lower the heat of reaction and subsequently survives a recycling step in the reaction. This experimentally and theoretically validated reaction mechanism may open a new pathway using bi-functional molten salts. Furthermore, the as-synthesized hollow porous silicon microsphere anodes show structural durability on cycling in both half/full cell tests, attributed to the high volume-accommodating ability. Thermochemical reduction of silica by molten salts is known to yield promising microstructured silica energy materials. Here a combined experimental and computational study suggests a mechanism for low temperature thermochemical reduction of silica by molten aluminum chloride.
ISSN:2399-3669
2399-3669
DOI:10.1038/s42004-018-0041-z