Sodium silicide (NaSi, Na4Si4) is a binary inorganic compound consisting of sodium and silicon. It is a solid black or grey crystalline material.Material Safety Data Sheet, SiGNa Chemistry, Inc. It can be synthesized by melting sodium or a sodium-potassium alloy with finely powdered silica gel. Temperature control of the reaction determine the final product's reactivity; heating above 400 °C creates an air-stable and less reducing product, while the product produced at room temperature is a pyrophoric and highly moisture-sensitive powder.Dye, J. L., Cram, K. D., Urbin, S. A., Redko, M. Y., Jackson, J. E., & Lefenfeld, M. (2005). Alkali Metals Plus Silica Gel: Powerful Reducing Agents and Convenient Hydrogen Sources. Journal of the American Chemical Society, 127(26), 9338–9339. https://doi.org/10.1021/ja051786+
Sodium silicide's empirical formula (NaSi) is deceptive, as it is a Zintl phase: instead of containing discrete anions, it contains tetrahedra, which leads to the more descriptive formula Na4Si4. These silicon tetrahedra condense into various crosslinked silicon polymers at high pressure.Cabrera, R. Q., Salamat, A., Barkalov, O. I., Leynaud, O., Hutchins, P., Daisenberger, D., Machon, D., Sella, A., Lewis, D. W., & McMillan, P. F. (2009). Pressure-induced structural transformations of the Zintl phase sodium silicide. Journal of Solid State Chemistry, 182(9), 2535–2542. https://doi.org/10.1016/j.jssc.2009.06.037
Sodium silicide reacts readily with water yielding gaseous hydrogen and aqueous sodium silicate in an exothermic reaction (~175 kJ·mol−1):Hydrogen Production from Sodium Silicide Powder; Prospects for On-Board Generation, 14 July 2006 2 NaSi + 5 H2O → 5 H2 + Na2Si2O5
This is used in hydrogen technologies to generate hydrogen as a fuel. It is also used as high energy dense storage for hydrogen under low pressure.
See also Silicide Binary compounds of silicon
External links SiGNa Chemistry, Inc.
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